Vaccines doi: 10.3390/vaccines13080840

Authors: Shuhan Zheng Xuan Deng Li Li Feng Luo Hanqing He Ying Wang Xiaoping Xu Shenyu Wang Yingping Chen

Background: Cervical cancer poses a threat to the health of women globally. Adolescent girls are the primary target population for HPV vaccination, and guardians’ attitude towards the HPV vaccine plays a significant role in determining the vaccination status among adolescent girls. Objectives: This study aimed to explore the factors influencing guardians’ HPV vaccine acceptance for their girls and provide clues for the development of health intervention strategies. Methods: Combining the health belief model as a theoretical framework, a questionnaire-based survey was conducted. A total of 2157 adolescent girls and their guardians were recruited. The multivariable logistic model was applied to explore associated factors. Results: The guardians had a high HPV vaccine acceptance rate (86.7%) for their girls, and they demonstrated a relatively good level of awareness regarding HPV and HPV vaccines. Factors influencing guardians’ HPV vaccine acceptance for girls included guardians’ education background (OR = 0.57, 95%CI = 0.37–0.87), family income (OR = 1.94, 95%CI = 1.14–3.32), risk of HPV infection (OR = 3.15, 95%CI = 1.40–7.10) or importance of the HPV vaccine for their girls (OR = 6.70, 95%CI = 1.61–27.83), vaccination status surrounding them (OR = 2.03, 95%CI = 1.41–2.92), awareness of negative information about HPV vaccines (OR = 0.59, 95%CI = 0.43–0.82), and recommendations from medical staff (OR = 2.32, 95%CI = 1.65–3.25). Also, guardians preferred to get digital information on vaccines via government or CDC platforms, WeChat platforms, and medical knowledge platforms. Conclusions: Though HPV vaccine willingness was high among Chinese guardians, they preferred to vaccinate their daughters at the age of 17–18 years, later than WHO’s recommended optimal age period (9–14 years old), coupled with safety concerns. Future work should be conducted based on these findings to explore digital intervention effects on girls’ vaccination compliance.

Vaccines doi: 10.3390/vaccines13080839

Authors: Mioljub Risti? Vladimir Vukovi? Smiljana Raj?evi? Marko Koprivica Nikica Agbaba Vladimir Petrovi?

Background/Objectives: Mumps remains a relevant vaccine-preventable disease globally, especially in settings where immunization coverage fluctuates or vaccine-induced immunity wanes. This study aimed to assess long-term trends in mumps incidence, vaccination coverage, clinical outcomes, and demographic characteristics in the Autonomous Province of Vojvodina (AP Vojvodina), Serbia, over a 47-year period. Methods: We conducted a retrospective observational study using surveillance data from the Institute of Public Health of Vojvodina. Analyses included annual mumps incidence rates (1978–2024), coverage with mumps-containing vaccines (MuCVs; 1986–2024), monthly case counts, and individual-level case data for the 1997–2024 period. Variables analyzed included age, month of notification, gender, vaccination status, presence of clinical complications, and the method used for case confirmation. Results: Following the introduction of MuCV in 1986, the mumps incidence markedly declined, with limited resurgences in 2000, 2009, and 2012. Between 1997 and 2024, a total of 1358 cases were reported, with 62.7% occurring in males. Over time, the age distribution shifted, with adolescents and young adults being increasingly affected during the later (2011–2024) observed period. In 2012, the highest age-specific incidence was observed among individuals aged 10–19 and 20–39 years (49.1 and 45.5 per 100,000, respectively). Vaccination coverage for both MuCV doses was suboptimal in several years. The proportion of unvaccinated cases decreased over time, while the proportion with unknown vaccination status increased. Mumps-related complications—such as orchitis, pancreatitis, and meningitis—were rare and predominantly affected unvaccinated individuals: 84.2% of orchitis, 40.0% of pancreatitis, and all meningitis cases. Only two pancreatitis cases (40.0%) were reported after one MMR dose, while fully vaccinated individuals (two doses) had one orchitis case (5.3%) and no other complications. Laboratory confirmation was applied more consistently from 2009 onward, with 49.6% of cases confirmed that year (58 out of 117), and, in several years after 2020, only laboratory-confirmed cases were reported, indicating improved diagnostic capacity. Conclusions: Despite substantial progress in controlling mumps, gaps in vaccine coverage, waning immunity, and incomplete vaccination records continue to pose a risk for mumps transmission. Strengthening routine immunization, ensuring high two-dose MuCV coverage, improving vaccination record keeping, and enhancing laboratory-based case confirmation are critical. Consideration should be given to booster doses in high-risk populations and to conducting a seroepidemiological study to estimate the susceptible population for mumps in AP Vojvodina.

Vaccines doi: 10.3390/vaccines13080838

Authors: Maria Costantino Mariagrazia Bathilde Marongiu Maria Grazia Corbo Anna Maria Della Corte Anna Rita Frascogna Angela Plantulli Federica Campana Luigi Fortino Emanuela Santoro Emilia Anna Vozzella Walter Longanella Giovanni Boccia Amelia Filippelli Francesco De Caro

Background: RSV remains a leading cause of infant hospitalization worldwide, and the recently approved nirsevimab could represent an effective and safe prophylactic strategy to prevent severe infections in the general neonatal population. Objectives: We conducted a retrospective observational monocentric pilot study in a mixed preterm/term birth cohort to add real-world evidence of the efficacy and safety of nirsevimab in preventing severe RSV infection. Methods: We included a total of 2035 consecutive infants admitted to the Neonatal Unit, University Hospital “San Giovanni di Dio e Ruggi d’Aragona”, Salerno, Italy, from November 2024 to April 2025. We evaluated 30-day safety profiles and season-wide RSV infection rates, and the outcomes were also compared to newborns’ birth rate in the two previous seasons (2022–2023 and 2023–2024). Results: After the introduction of nirsevimab, a lower RSV infection rate was reported compared to previous seasons, and no adverse effects were observed. Compared to previous seasons, the clinical outcomes were more favorable, as only one unvaccinated neonate with RSV infection required invasive ventilation. Conclusions: In this real-world analysis, we demonstrated a good short-term safety profile of nirsevimab, as well as a potentially high efficacy in the general neonatal population with lower RSV infection incidence. However, future studies are needed to better assess its long-term safety and season-wide efficacy.

Vaccines doi: 10.3390/vaccines13080837

Authors: Yongming Sang Samuel N. Nahashon Richard J. Webby

Highly pathogenic avian influenza (HPAI) remains a persistent threat to global poultry production and public health. Current vaccine platforms show limited cross-clade efficacy and often fail to induce mucosal immunity. Recent advances in microbiome research reveal critical roles for gut commensals in modulating vaccine-induced immunity, including enhancement of mucosal IgA production, CD8+ T-cell activation, and modulation of systemic immune responses. Engineered commensal bacteria such as Lactococcus lactis, Bacteroides ovatus, Bacillus subtilis, and Staphylococcus epidermidis have emerged as promising live vectors for antigen delivery. Postbiotic and synbiotic strategies further enhance protective efficacy through targeted modulation of the gut microbiota. Additionally, artificial intelligence (AI)-driven tools enable predictive modeling of host–microbiome interactions, antigen design optimization, and early detection of viral antigenic drift. These integrative technologies offer a new framework for mucosal, broadly protective, and field-deployable vaccines for HPAI control. However, species-specific microbiome variation, ecological safety concerns, and scalable manufacturing remain critical challenges. This review synthesizes emerging evidence on microbiome–immune crosstalk, commensal vector platforms, and AI-enhanced vaccine development, emphasizing the urgent need for One Health integration to mitigate zoonotic adaptation and pandemic emergence.

Vaccines doi: 10.3390/vaccines13080836

Authors: Zhen Lin Zegang Chen Lijiao Pei Yueyun Chen Zhenyu Ding

Lung cancer remains one of the most prevalent and lethal malignancies worldwide. Although conventional treatments such as surgery, chemotherapy, and radiotherapy have modestly improved patient survival, their overall efficacy remains limited, and the prognosis is generally poor. In recent years, immunotherapy, particularly immune checkpoint inhibitors, has revolutionized cancer treatment. Nevertheless, the immunosuppressive tumor microenvironment, tumor heterogeneity, and immune escape mechanisms significantly restrict the clinical benefit, which falls short of expectations. Within this context, cancer vaccines have emerged as a promising immunotherapeutic strategy. By activating the host immune system to eliminate tumor cells, cancer vaccines offer high specificity, low toxicity, and the potential to induce long-lasting immune memory. These advantages have positioned them as a focal point in cancer immunotherapy research. This paper provides a comprehensive overview of recent clinical advances in lung cancer vaccines, discusses the major challenges impeding their clinical application, and explores potential strategies to overcome these barriers.

Vaccines doi: 10.3390/vaccines13080835

Authors: Delphine Béland Victor Mullins-Dansereau Karen Geoffroy Mélissa Viens Kim Leclerc Desaulniers Marie-Claude Bourgeois-Daigneault

Background/Objectives: Leukemia is associated with high recurrence rates and cancer vaccines are emerging as a promising immunotherapy against the disease. Here, we investigate the mechanism of action by which a personalized vaccine made from leukemia cells infected with an oncolytic virus (ICV) induces anti-tumor immunity. Methods: Using the L1210 murine model, leukemia cells were infected and irradiated to create the ICV. The CRISPR-Cas9 system was used to engineer knockout cells to test in treatment efficacy studies. Results: We found that pro-inflammatory interferons (IFNs) that are produced by infected vaccine cells induce the immunoproteasome (ImP), a specialized proteasome subtype that is found in immune cells. Interestingly, we show that while a vaccine using the oncolytic vesicular stomatitis virus (oVSV) completely protects against tumor challenge, the wild-type (wt) virus, which does not induce the ImP, is not as effective. To delineate the contribution of the ImP for vaccine efficacy, we generated ImP-knockout cell lines and found no differences in treatment efficacy compared to wild-type cells. Furthermore, an ICV using another murine leukemia model that expresses the ImP only when infected by an IFN gamma-encoding variant of the virus demonstrated similar efficacy as the parental virus. Conclusions: Taken together, our data show that ImP expression by vaccine cells was not required for the efficacy of leukemia ICVs.

Vaccines doi: 10.3390/vaccines13080834

Authors: Guillaume Demare Elgiraud Ramarosaiky Zavaniarivo Rampanjato Nadine Muller Beate Kampmann Hanna-Tina Fischer

Despite growing global momentum to reduce the number of children who never received a dose of any vaccine, i.e., zero-dose (ZD) children, persistent geographic and social inequities continue to undermine progress toward universal immunization coverage. In Madagascar, where routine vaccination coverage remains below 50% in most regions, the non-governmental organization Doctors for Madagascar and public sector partners are implementing the SOAMEVA program: a targeted community-based initiative to identify and reach ZD children in sixteen underserved districts in the country’s south. This paper outlines the equity-sensitive evaluation design developed to assess the implementation and impact of SOAMEVA. It presents a forward-looking evaluation framework that integrates both quantitative program monitoring and qualitative community insights. By focusing at the fokontany level—the smallest administrative unit in Madagascar—the evaluation captures small-scale variation in ZD prevalence and program reach, allowing for a detailed analysis of disparities often masked in aggregated data. Importantly, the evaluation includes structured feedback loops with community health workers and caregivers, surfacing local knowledge on barriers to immunization access and program adoption. It also tracks real-time adaptations to implementation strategy across diverse contexts, offering insight into how routine immunization programs can be made more responsive, sustainable, and equitable. We propose eight design principles for conducting equity-sensitive evaluation of immunization programs in similar fragile settings.

Vaccines doi: 10.3390/vaccines13080833

Authors: Theocharis Anastasiou Elias Sanidas Thekla Lytra Georgios Mimikos Helen Gogas Marina Mantzourani

The association between COVID-19 vaccination and thromboembolic events has garnered significant research attention, particularly with the advent of vaccines based on adenoviral vectors, including AstraZeneca’s and Johnson & Johnson’s vaccines. This review underscores the uncommon occurrence of venous thromboembolism (VTE), arterial thromboembolism (ATE), and vaccine-induced thrombotic thrombocytopenia (VITT) following COVID-19 vaccination. Although these complications are extremely rare compared to the heightened risk of thrombosis from COVID-19 infection, elements like age, biological sex, type of vaccine and underlying health conditions may contribute to their development. In addition, rare renal complications such as acute kidney injury and thrombotic microangiopathy have been documented, broadening the spectrum of potential vaccine-associated thrombotic manifestations. Current guidelines emphasize early detection, individualized risk assessment, and use of anticoagulation therapy to mitigate risks. Despite these events, the overwhelming majority of evidence supports the continued use of COVID-19 vaccines, given their proven efficacy in reducing severe illness and mortality. In addition, recent comparative data confirm that mRNA-based vaccines are associated with a significantly lower risk of serious thrombotic events compared to adenoviral vector platforms. Ongoing research is essential to further refine preventive and therapeutic strategies, particularly for at-risk populations.

Vaccines doi: 10.3390/vaccines13080832

Authors: Jacqueline Pearce Ellen Versmissen David Sutton Qi Cao Ian Tarpey

Background/Objectives: Typically, studies aiming to assess the ability of canine parvovirus (CPV) vaccines to immunise puppies with maternally derived antibody (MDA) are undertaken using group-housed puppies. Since live attenuated vaccine virus is invariably shed in the faeces, this can result in repeated oral re-exposure and puppies which failed to respond to the initial vaccination may respond instead to shed vaccine virus in the environment, thus artificially enhancing the efficacy of the vaccine. This problem can be avoided by adopting a pair-housed study design where one vaccinated pup is housed with one unvaccinated sentinel. Using this design, we examine the capability of four commercially available canine parvovirus vaccines to immunise MDA-positive pups. Methods: Thirty-four 6-week-old puppies born to vaccinated dams were divided into four vaccine groups with similar MDA ranges. Within each group puppies were paired based on matching MDA titres, and each pair was housed in separate biocontainment accommodation. In each pair, the pup with the highest MDA was vaccinated and the other left as an unvaccinated sentinel. All vaccinates were given a single dose of one of the vaccines. Vaccinates and sentinels were then bled every 2–4 days and CPV antibody was measured. Daily rectal swabs were also collected from all pups to identify any shed vaccinal CPV. Results: All the pups vaccinated with Nobivac DP PLUS seroconverted, with significantly higher antibody titres compared to the pups in other vaccine groups, all shed vaccine virus, and all bar one of the sentinel pups seroconverted. In the other groups, only vaccinated pups with lower levels of MDA seroconverted and shed vaccine virus but none of the sentinel pups seroconverted. Conclusions: Different canine parvovirus vaccines differ in their ability to replicate in and immunise puppies with MDA, the levels of which may vary widely between individuals. The shedding of vaccinal CPV is an important consideration when designing studies to demonstrate efficacy in MDA-positive puppies.

Vaccines doi: 10.3390/vaccines13080830

Authors: Yannan Yin Jinkai Zang Huichun Shi Zhuang Wang Linlin Kuang Shuxia Wang Haikun Wang Ning Li Xiaozhen Liang Zhong Huang

Background: It is still challenging to develop effective vaccines against tumorigenic human gammaherpesviruses such as Epstein–Barr virus (EBV). A major obstacle is the lack of a small animal model that reproduces the natural infection course of human gammaherpesviruses to allow for proper assessment of vaccine efficacy. Murine gammaherpesvirus 68 (MHV68) is a natural pathogen of wild rodents and laboratory mice and therefore can be used as a surrogate for human gammaherpesviruses to evaluate vaccination strategies. Methods: In this study, two mRNA vaccine candidates were generated, one encoding a fusion protein of the MHV68 gH with the gL (gHgL-mRNA) and the other expressing the MHV68 gB protein (gB-mRNA). The immunogenicity and protective efficacy of the mRNA vaccine candidates were evaluated in a mouse model of MHV68 infection. Results: The gHgL-mRNA but not the gB-mRNA candidate vaccine was able to induce neutralizing antibodies in mice, whereas both vaccines could elicit antigen-specific T-cell responses. Following MHV68 intranasal inoculation, complete blocking of the establishment of viral latency was observed in some mice immunized with individual gHgL-mRNA or gB-mRNA vaccines. Notably, co-immunization with the two mRNA vaccines appeared to be more effective than individual vaccines, achieving sterile immunity in 50% of the vaccinated mice. Conclusions: This study demonstrates that immunization with mRNA platform-based subunit vaccines is indeed capable of preventing MHV68 latent infection, thus validating a safe and efficacious vaccination strategy that may be applicable to human gammaherpesviruses.

Vaccines doi: 10.3390/vaccines13080831

Authors: Kristen Feemster William P. Hausdorff Natalie Banniettis Heather Platt Priscilla Velentgas Alejandra Esteves-Jaramillo Robert L. Burton Moon H. Nahm Ulrike K. Buchwald

The authors would like to make the following corrections to this published paper [...]

Vaccines doi: 10.3390/vaccines13080829

Authors: Andzoa N. Jamus Zoe E. R. Wilton Samantha D. Armijo Julian Flanagan Isabella G. Romano Susan B. Core Kathryn M. Frietze

Background/Objectives: Intramuscular immunization elicits systemic IgG and is the primary route of vaccine administration in humans. However, there is growing interest in utilizing other routes of administration to tailor antibody profiles, increase immunity at primary sites of infection, simplify administration, and eliminate needle waste. Here, we investigated the antibody profiles elicited by immunization with bacteriophage virus-like particle vaccine platforms at various routes of administration. Methods: We chose two model bacteriophage vaccines for investigation: bacteriophage MS2 virus-like particles (VLPs) recombinantly displaying a short, conserved peptide from Chlamydia trachomatis major outer membrane protein (MS2) and bacteriophage Qβ VLPs displaying oxycodone through chemical conjugation (Qβ). We comprehensively characterized the antibodies elicited systemically and at various mucosal sites when the vaccines were administered intramuscularly, intranasally or periocularly with or without an intramuscular prime using various prime/boost schemes. Results: Intranasal and periocular immunization elicited robust mucosal and systemic IgA responses for both MS2 and Qβ. The intramuscular prime followed by intranasal or periocular boosts elicited broad antibody responses, and increased antibodies titers at certain anatomical sites. Conclusions: These findings demonstrate the tractability of bacteriophage VLP-based vaccines in generating specific antibody profiles based on the prime–boost regimen and route of administration.

Vaccines doi: 10.3390/vaccines13080828

Authors: Van Hung Nguyen Pascal Crepey B. Adam Williams Verna L. Welch Jean Marie Pivette Charles H. Jones Jane M. True

Background/Objectives: An influenza pandemic is likely to occur in the coming decades and will be associated with substantial healthcare and financial burdens. In this study, we evaluated the potential economic costs of different vaccination scenarios for the US population in the context of a moderate or severe influenza pandemic. Methods: Economic analysis was performed for initiation of pandemic vaccination from 3 months vs. 6 months in the US after declaration of a pandemic. We evaluated three vaccine effectiveness levels (high, moderate, low) and two pandemic severity levels (moderate and severe). Results: No vaccination would lead to total direct and indirect costs of $116 bn in a moderate pandemic and $823 bn in a severe pandemic. Initiation of vaccination at 3 months would result in cost savings versus no vaccination (excluding vaccine price) of $30–84 bn and $260–709 bn in a moderate and severe pandemic, respectively, whereas initiation of vaccination at 6 months would result in cost savings of $4–11 bn and $36–97 bn, respectively. Cost savings of $20 bn and $162 bn would occur in a moderate or severe pandemic, respectively, from use of a low effectiveness vaccine from 3 months instead of a high effectiveness vaccine from 6 months. Conclusions: Rapid initiation of vaccination would have a greater impact than increased vaccine effectiveness in reducing the economic impacts of an influenza pandemic.

Vaccines doi: 10.3390/vaccines13080827

Authors: Kumar Ilangovan David Radley Michael Patton Emma Shittu Maria Maddalena Lino Christos Goulas Kena A. Swanson Annaliesa S. Anderson Alejandra Gurtman Iona Munjal

Background/objectives: This was a post hoc analysis of safety data across the bivalent respiratory syncytial virus prefusion F (RSVpreF) vaccine clinical trial development program. Methods: Data from eight clinical trials in 46,913 immunocompetent adults who received RSVpreF or placebo were analyzed. Local reactions and systemic events were assessed among non-pregnant ≥18-year-olds (n = 9517); adverse events (AEs) among pregnant and non-pregnant 18–59-year-olds (n = 9238); and vaccine-related AEs among non-pregnant ≥18-year-olds (n = 39,314). Post-marketing data in non-pregnant adults were considered. Results: Local reactions and systemic events were reported more frequently in RSVpreF versus placebo recipients; injection site pain was the most common local reaction (RSVpreF, 18.9%; placebo, 7.4%), and fatigue (23.5%; 18.4%) and headache (19.5%; 15.0%) were the most common systemic events. Percentages of AEs within 1 month after vaccination were similar across groups (RSVpreF, 12.8%; placebo, 13.1%); severe AEs were reported in ≤1.5% of participants. Differences in percentages of individuals reporting vaccine-related AEs between the RSVpreF and placebo groups were <0.2% for all related AEs. Serious AEs throughout the study were reported in ≤14.0% (RSVpreF, 12.6%; placebo, 14.0%). No atrial fibrillation, Guillain-Barré syndrome, or acute polyneuropathy cases were reported. The AE data from post-marketing data sources were consistent with the safety profile from the clinical trial program, with no new safety concerns. Conclusions: Integrated data demonstrated that RSVpreF was well tolerated with a favorable safety profile in non-pregnant and pregnant adults. Ongoing surveillance through real-world use and clinical trial experience continue to support the safety profile of RSVpreF. ClinicalTrials.gov: NCT03529773/NCT04071158/NCT04785612/NCT05035212/NCT05096208/NCT05842967/NCT04032093/NCT04424316.

Vaccines doi: 10.3390/vaccines13080826

Authors: Lili Huang Guangfu Li Yuhui Zhang Xue Zhao Kai Wang Chunyu Jia Wei Zhang Jiebing Tan Xiaofen Chen Qin Li Hongyan Jiang Rui An Wenna Leng Yongli Yang Youcai An Yanxia Wang Yaodong Zhang

The authors would like to make the following corrections to this published paper [...]

Vaccines doi: 10.3390/vaccines13080825

Authors: Jiaqi Chen Weitong Lin Chaokai Yang Wenqi Lin Xinghui Cheng Haoyuan He Xinhua Li Jingyou Yu

Background/Objectives: Mucosal vaccines, delivered intranasally or via inhalation, are being studied for respiratory infectious diseases like COVID-19 and influenza. These vaccines aim to provide non-invasive administration and strong immune responses at infection sites, making them a promising area of research. This systematic review and meta-analysis assessed their immunogenicity, safety, and protective efficacy. Methods: The study design was a systematic review and meta-analysis, searching PubMed and Cochrane databases up to 30 May 2025. Inclusion criteria followed the PICOS framework, focusing on mucosal vaccines for COVID-19, influenza, RSV, pertussis, and tuberculosis. Results: A total of 65 studies with 229,614 participants were included in the final analysis. Mucosal COVID-19 vaccines elicited higher neutralizing antibodies compared to intramuscular vaccines (SMD = 2.48, 95% CI: 2.17–2.78 for wild-type; SMD = 1.95, 95% CI: 1.32–2.58 for Omicron), with varying efficacy by route (inhaled VE = 47%, 95% CI: 22–74%; intranasal vaccine VE = 17%, 95% CI: 0–31%). Mucosal influenza vaccines protected children well (VE = 62%, 95% CI: 30–46%, I2 = 17.1%), but seroconversion rates were lower than those of intramuscular vaccines. RSV and pertussis vaccines had high seroconversion rates (73% and 52%, respectively). Tuberculosis vaccines were reviewed systemically, exhibiting robust cellular immunogenicity. Safety was comparable to intramuscular vaccines or placebo, with no publication bias detected. Conclusions: Current evidence suggests mucosal vaccines are immunogenic, safe, and protective, particularly for respiratory diseases. This review provides insights for future research and vaccination strategies, though limitations include varying efficacy by route and study heterogeneity.

Vaccines doi: 10.3390/vaccines13080822

Authors: Gabriela Zambrano-Sánchez Josue Rivadeneira Carlos Manterola Tamara Otzen Luis Fuenmayor-González

Introduction: Long COVID syndrome is defined as persistent or new symptoms that appear after an acute SARS-CoV-2 infection and last at least three months without explanation. It is estimated that between 10% and 20% of those infected develop long COVID; however, data is not precise in Latin America. Although high immunization rates have reduced acute symptoms and the pandemic’s impact, there is a lack of evidence of its efficacy in preventing long COVID in the region. Methods: This scoping review followed PRISMA-ScR guidelines. Studies on vaccinated adults with long COVID from Central and South America and the Caribbean were included (Mexico was also considered). A comprehensive search across multiple databases was conducted. Data included study design, participant characteristics, vaccine type, and efficacy outcomes. Results are presented narratively and in tables. Results: Out of 3466 initial records, 8 studies met the inclusion criteria after rigorous selection processes. These studies encompassed populations from Brazil, Mexico, Latin America, and Bonaire, with 11,333 participants, 69.3% of whom were female. Vaccination, particularly with three or more doses, substantially reduces the risk and duration of long COVID. Variability was noted in the definitions and outcomes assessed across studies. Conclusions: This scoping review highlights that SARS-CoV-2 vaccination exhibits potential in reducing the burden of long COVID in the Americas. However, discrepancies in vaccine efficacy were observed depending on the study design, the population studied, and the vaccine regimen employed. Further robust, region-specific investigations are warranted to delineate the effects of vaccination on long COVID outcomes.

Vaccines doi: 10.3390/vaccines13080824

Authors: Dmitry D. Zhdanov Anastasia N. Shishparenok Yury Y. Ivin Anastasia A. Kovpak Anastasia N. Piniaeva Igor V. Levin Sergei V. Budnik Oleg A. Shilov Roman S. Churyukin Lubov E. Agafonova Alina V. Berezhnova Victoria V. Shumyantseva Aydar A. Ishmukhametov

Objectives: Most antiviral vaccines are created by inactivating the virus using chemical methods. The inactivation and production of viral vaccine preparations after the irradiation of viruses with accelerated electrons has a number of significant advantages. Determining the integrity of the genome of the resulting viral particles is necessary to assess the quality and degree of inactivation after irradiation. Methods: This work was performed on the Sabin 2 model polio virus. To determine the most sensitive and most radiation-resistant part, the polio virus genome was divided into 20 segments. After irradiation at temperatures of 25 °C, 2–8 °C, −20 °C, or −70 °C, the amplification intensity of these segments was measured in real time. Results: The best correlation between the amplification cycle and the irradiation dose at all temperatures was observed for segment 3D, left. Consequently, this section of the poliovirus genome is the least resistant to the action of accelerated electrons and is the most representative for determining genome integrity. The worst dependence was observed for the VP1 right section, which, therefore, cannot be used to determine genome integrity during inactivation. The electrochemical approach was also employed for a comparative assessment of viral RNA integrity before and after irradiation. An increase in the irradiation dose was accompanied by an increase in signals indicating the electrooxidation of RNA heterocyclic bases. The increase in peak current intensity of viral RNA electrochemical signals confirmed the breaking of viral RNA strands during irradiation. The shorter the RNA fragments, the greater the peak current intensities. In turn, this made the heterocyclic bases more accessible to electrooxidation on the electrode. Conclusions: These results are necessary for characterizing the integrity of the viral genome for the purpose of creating of antiviral vaccines.

Vaccines doi: 10.3390/vaccines13080823

Authors: Adolfo Loayza Alicia Hernandez Ana M. Rodriguez Belen Lopez Cristina Gonzalez David Hardisson Itziar de la Pena Maria Serrano Rocio Arnedo Ignacio Zapardiel

Introduction: Following up on treated high-grade cervical intraepithelial neoplasia (HSIL/CIN) lesions poses a challenge. Cervical cytology often has a high false-negative rate, while high-risk human papillomavirus (HR-HPV) DNA testing, though sensitive, lacks specificity. The detection of messenger RNA of the HR-HPV E6 and E7 oncoproteins (E6/E7 mRNA) is proposed as an indicator of viral integration, which is crucial for identifying severe lesions. Additionally, HPV vaccination could reduce recurrence rates in patients treated for high-grade cervical intraepithelial neoplasia. Objective: Our study aimed to assess the clinical utility of E6/E7 mRNA determination in the follow-up of HPV-immunized patients who were treated for HSIL/CIN. Methods: We conducted a retrospective observational study including 407 patients treated for HSIL/CIN. The recurrence rate and the validity parameters of E6/E7 mRNA testing were analyzed. Results: The recurrence rate for high-grade lesions was 1.7%. This low percentage might be related to the vaccination of patients who were not immunized before treatment. The sensitivity of the E6/E7 mRNA test was 88% at the first clinical visit, reaching 100% in the second and third reviews. Specificity was 91% at the first visit, 92% at the second, and 85% at the third. Regarding predictive values, the positive predictive value was 18% at the first visit, 10% at the second, and 14% at the third, while the negative predictive value was 100% across all follow-up visits. Conclusions: The E6/E7 mRNA test appears to be an effective tool for ruling out recurrence after treatment for HSIL/CIN lesions in HPV-immunized patients.

Vaccines doi: 10.3390/vaccines13080821

Authors: Yang-Yang Zhao Fu-Ming Zhu Yong-Juan Zhang Huanhuan Y. Wei

Circular RNAs (circRNAs) have emerged as a transformative class of RNA therapeutics, distinguished by their closed-loop structure conferring nuclease resistance, reduced immunogenicity, and sustained translational activity. While challenges in pharmacokinetic control and manufacturing standardization require resolution, emerging synergies between computational design tools and modular delivery platforms are accelerating clinical translation. In this review, we synthesize recent advances in circRNA therapeutics, with a focused analysis of their stability and immunogenic properties in vaccine and drug development. Notably, key synthesis strategies, delivery platforms, and AI-driven optimization methods enabling scalable production are discussed. Moreover, we summarize preclinical and emerging clinical studies that underscore the potential of circRNA in vaccine development and protein replacement therapies. As both a promising expression vehicle and programmable regulatory molecule, circRNA represents a versatile platform poised to advance next-generation biologics and precision medicine.

Vaccines doi: 10.3390/vaccines13080819

Authors: Billy J. Erazo Flores Laura J. Knoll

Toxoplasma gondii is an intracellular protozoan found worldwide that is capable of infecting nearly all warm-blooded animals, including humans. Its parasitic success lies in its capacity to create chronic infections while avoiding immune detection, altering host immune responses, and disrupting programmed cell death pathways. This review examines the complex relationship between T. gondii and host immunity, focusing on how the parasite influences innate and adaptive immune responses to survive in immune-privileged tissues. We present recent findings on the immune modulation specific to various parasite strains, the immunopathology caused by imbalanced inflammation, and how the parasite undermines host cell death mechanisms such as apoptosis, necroptosis, and pyroptosis. These immune evasion tactics enable prolonged intracellular survival and pose significant challenges for treatment and vaccine development. We also review advancements in therapeutic strategies, including host-directed approaches, nanoparticle drug delivery, and CRISPR-based technologies, along with progress in vaccine development from subunit and DNA vaccines to live-attenuated candidates. This review emphasizes the importance of T. gondii as a model for chronic infections and points out potential avenues for developing innovative therapies and vaccines aimed at toxoplasmosis and similar intracellular pathogens.

Vaccines doi: 10.3390/vaccines13080820

Authors: Barry Lorbetskie Narges Manouchehri Michel Girard Simon Sauvé Huixin Lu

One concern in the yearly re-formulation of influenza vaccines is the time-consuming manufacturing of vaccine potency reagents, particularly for emergency responses. The continuous evaluation of modern techniques such as reversed-phase (RP) chromatography is an asset for streamlining this process. One challenge with RP methods, however, is the need to re-optimize methods for antigens that show poor separation, which can be highly dependent on analyst experience and available data. In this study, we leveraged a large RP dataset of influenza antigens to explore machine learning (ML) approaches of classifying challenging separations for computer-assisted method re-optimization across years, products, and analysts. Methods: To address recurring chromatographic issues—such as poor resolution, strain co-elution, and signal absence—we applied data augmentation techniques to correct class imbalance and trained multiple supervised ML classifiers to distinguish between these peak profiles. Results: With data augmentation, several ML models demonstrated promising accuracy in classifying chromatographic profiles according to the provided labels. These models effectively distinguished patterns indicative of separation issues in real-world data. Conclusions Our findings highlight the potential of ML as a computer assisted tool in the evaluation of vaccine quality, offering a scalable and objective approach to chromatogram classification. By reducing reliance on manual interpretation, ML can expedite the optimization of analytical methods, which is particularly needed for rapid responses. Future research involving larger, inter-laboratory datasets will further elucidate the utility of ML in vaccine analysis.

Vaccines doi: 10.3390/vaccines13080818

Authors: Alma Cárdenas-Flores Minerva Camacho-Nuez Massaro W. Ueti Mario Hidalgo-Ruiz Angelina Rodríguez-Torres Diego Josimar Hernández-Silva José Guadalupe Gómez-Soto Masahito Asada Shin-ichiro Kawazu Alma R. Tamayo-Sosa Rocío Alejandra Ruiz-Manzano Juan Mosqueda

Background: Bovine babesiosis, caused by the tick-borne apicomplexan parasite Babesia spp., is an economically significant disease that threatens the cattle industry worldwide. Babesia bovis is the most pathogenic species, leading to high morbidity and mortality in infected animals. One promising approach to vaccination against bovine babesiosis involves the use of multiple protective antigens, offering advantages over traditional live-attenuated vaccines. Tools such as immunobioinformatics and reverse vaccinology have facilitated the identification of novel antigens. Enolase, a “moonlighting” enzyme of the glycolytic pathway with demonstrated vaccine potential in other pathogens, has not yet been studied in B. bovis. Methods: In this study, the enolase gene from two B. bovis isolates was successfully identified and sequenced. The gene, consisting of 1366 base pairs, encodes a predicted protein of 438 amino acids. Its expression in intraerythrocytic parasites was confirmed by RT-PCR. Two peptides containing predicted B-cell epitopes were synthesized and used to immunize rabbits. Hyperimmune sera were then analyzed by ELISA, confocal microscopy, Western blot, and an in vitro neutralization assay. Results: The hyperimmune sera showed high antibody titers, reaching up to 1:256,000. Specific antibodies recognized intraerythrocytic merozoites by confocal microscopy and bound to a ~47 kDa protein in erythrocytic cultures of B. bovis as detected by Western blot. In the neutralization assay, antibodies raised against peptide 1 had no observable effect, whereas those targeting peptide 2 significantly reduced parasitemia by 71.99%. Conclusions: These results suggest that B. bovis enolase contains B-cell epitopes capable of inducing neutralizing antibodies and may play a role in parasite–host interactions. Enolase is therefore a promising candidate for further exploration as a vaccine antigen. Nonetheless, additional experimental studies are needed to fully elucidate its biological function and validate its vaccine potential.

Vaccines doi: 10.3390/vaccines13080817

Authors: Xi Wang Xinyue Cui Chongyang Wu Ke Tao Shuyuan Pan Wenming Wei

Background/Objectives: Chemically or genetically detoxified pertussis toxin (PTx) is a crucial antigen component of the acellular pertussis vaccine. Chemical detoxification using glutaraldehyde generally causes significant structural changes to the toxin. However, how these structural changes in PTx affect its antigenic properties remains unclear. Additionally, there is limited knowledge regarding how many alterations in antigenic properties impact immunogenicity. Methods: To investigate the impact of structural changes on antigenic properties, we developed a sandwich ELISA to quantify the neutralizing epitopes on PTx. Subsequently, we analyzed different PTx toxoid (PTd) preparations with the assay. Additionally, we assessed the immunogenicity of various acellular pertussis vaccine candidates containing these PTd preparations. Finally, the assay was applied to evaluate the consistency of commercial batches of PTx and PTd intermediates. Results: The assay demonstrated reasonable specificity, accuracy, and precision, and it was sensitive enough to quantify variations in neutralizing epitopes among different PTd samples that shared the same protein concentration. Importantly, we found a positive correlation between the number of neutralizing epitopes in detoxified PTx and its immunogenicity, indicating that the amount of neutralizing epitopes present determines the immunogenicity of glutaraldehyde-inactivated PTx. Moreover, commercial batches of PTx and PTd intermediates exhibited minor variations in neutralizing epitopes. Conclusions: These findings have significant implications for developing acellular pertussis vaccines as they highlight the importance of preserving the neutralizing epitopes of PTx during detoxification to ensure the vaccine’s effectiveness. This assay is also valuable for the quality control of PTd as it more accurately represents the actual antigenic changes of PTx.

Vaccines doi: 10.3390/vaccines13080816

Authors: Lidia Stopyra Karolina Banach Magdalena Wood Justyna Stala Anna Merklinger-Grucha?a

Background: The 2022 conflict in Ukraine triggered mass migration, leading to a significant influx of Ukrainian refugee children into Poland. This situation raises concerns about hepatitis B virus immunity, as Ukraine’s hepatitis B vaccination coverage has been inconsistent compared to Poland’s high vaccination rates. Objective: To evaluate hepatitis B immunity and infection prevalence among Ukrainian refugee children residing in Southern Poland and to assess implications for vaccination strategies in the host country. Methods: A prospective cross-sectional study was conducted on 1322 Ukrainian refugee children (0–18 years) presenting to a pediatric infectious diseases department in Southern Poland between February 2022 and March 2024. Data on vaccination history, demographic characteristics, and selected laboratory parameters, including hepatitis B surface antigen and anti-HBs antibody levels, were collected. Protective immunity was defined as anti-HBs antibody levels ≥10 IU/L. Results: Among the participants (mean age 9.9 years; 50.2% female), 83.2% were reported as vaccinated according to national immunization programs, but only 64.9% demonstrated protective anti-HBs antibody levels. Protective antibody prevalence declined significantly with age, with less than half of adolescents aged 15–18 years showing immunity. Five children (0.4%) were diagnosed with chronic hepatitis B, four of whom were unvaccinated. Conclusions: This study identifies a significant gap in hepatitis B immunity among Ukrainian adolescent refugees residing in Southern Poland, with less than half possessing protective anti-HBs antibody levels. This immunity gap and the high risk of sexual transmission of the hepatitis B virus in adolescents highlight the urgent need for comprehensive surveillance, screening, and catch-up vaccination programs.

Vaccines doi: 10.3390/vaccines13080815

Authors: Filippo Liviero Anna Volpin Patrizia Furlan Silvia Cocchio Vincenzo Baldo Sofia Pavanello Angelo Moretto Fabriziomaria Gobba Alberto Modenese Marcella Mauro Francesca Larese Filon Angela Carta Maria Grazia Lourdes Monaco Gianluca Spiteri Stefano Porru Maria Luisa Scapellato

Background/Objectives: This retrospective multicenter study, conducted within the ORCHESTRA Project, investigated SARS-CoV-2 reinfections among 5777 healthcare workers (HCWs) from four University Hospitals (Modena, Verona, Padova and Trieste) in northern Italy, aiming to assess the risk of reinfection and its determinants, comparing the clinical characteristics of reinfections with those of first infections, and examining the impact of preventive measures and vaccination strategies. Methods: HCWs completed an online questionnaire between June and August 2022. The survey collected demographic, occupational, and clinical data, including information on first infections and reinfections. Statistical analyses were performed using SPSS 28.0, through bivariate and multivariate approaches. Results: Response rates were 41.8% for Modena, 39.5% for Verona, 17.9% for Padova, and 17.4% for Trieste. Among the respondents, 4.8% (n = 276) experienced 2 infections and 0.5% (n = 27) reported 3 infections, out of a total of 330 reinfection cases. Additionally, 43.0% (n = 2787) reported only one infection, while 51.5% were never infected. Reinfection rates increased across five study phases (based on the epidemiological context), likely due to the emergence of new SARS-CoV-2 variants. A booster vaccine dose significantly reduced reinfection risk. Higher reinfection risk was found among HCWs aged ≤30 years, those with chronic respiratory diseases, and those working in COVID-19 wards, particularly nurses and allied health professionals. Reinfections were associated with a lower frequency of symptoms both during the period of swab positivity and after a negative swab, as well as with a shorter duration of swab positivity. No significant differences in symptom duration were found between first infections and reinfections. Conclusions: Despite its limitations, the online questionnaire proved a useful tool. Natural infection and vaccination reduced both reinfection risk and symptom severity. Prior infections should be considered in planning vaccination schedules and prioritizing HCWs.

Vaccines doi: 10.3390/vaccines13080814

Authors: Mioljub Risti? Vladimir Vukovi? Smiljana Raj?evi? Sne?ana Medi? Marko Koprivica Vladimir Petrovi?

Background: Despite decades of high childhood vaccination coverage, pertussis has re-emerged in the Autonomous Province of Vojvodina (AP Vojvodina), Serbia. We aimed to describe the temporal, seasonal, and age-specific patterns of pertussis in AP Vojvodina and to analyze trends by vaccination status in order to highlight changes in epidemiology and potential gaps in vaccine-induced protection. Methods: We retrospectively analyzed 2796 pertussis cases reported between January 1997 and December 2024, examining temporal, seasonal, and age-specific trends, stratifying by vaccination status across four consecutive periods (1997–2003, 2004–2010, 2011–2017, and 2018–2024). Results: Throughout the 28-year period, after low and sporadic cases in the pre-2012 period, a dramatic rise was observed in 2014, 2017, and 2018, culminating in the highest annual number of reported cases in 2024 (1011 cases). Throughout this period, primary vaccination coverage with the DTwP/DTaP three-dose series ranged between 91% and 98%, while first booster coverage gradually declined from 98% in the early 2000s to 83% in 2024. Regarding seasonality, a sharp increase in cases began in 2012, peaking in November 2023 (>350 cases) and early 2024 (312 in January, 268 in February), with a seasonal shift from summer peaks in the 2011–2017 period to higher incidence rates during colder months more recently. Adolescents aged 10–14 years had the highest cumulative incidence (1149.4/100,000), followed by infants under 12 months (978.5/100,000), despite the latter representing fewer absolute cases. The proportion of pertussis in fully vaccinated individuals rose from 6.3% (1997–2003) to 49.7% (2018–2024). Conclusions: These findings suggest that booster immunization in adolescence and routine maternal vaccination during pregnancy could reduce transmission, particularly to infants. Enhanced surveillance and updated immunization policies are critical to mitigating future pertussis outbreaks.

Vaccines doi: 10.3390/vaccines13080813

Authors: Ersilia Buonomo Daniele Di Giovanni Gaia Piunno Stefania Moramarco Giuliana D’Elpidio Ercole Vellone Enkeleda Gjini Mariachiara Carestia Cristiana Ferrari Luca Coppeta

Background: Vaccine hesitancy (VH) represents a growing concern among healthcare professionals and students, potentially undermining public health efforts. Nursing, pediatric nursing, and midwifery students are future vaccinators and educators, making it essential to understand their attitudes, knowledge, and confidence toward vaccination. This study aims to assess vaccine-related perceptions and behaviors among these student populations in an Italian university. Methods: A cross-sectional survey was conducted between November 2022 and February 2024 at the University of Rome “Tor Vergata”. A structured, anonymous questionnaire, including the Vaccination Attitudes Examination (VAX) scale, vaccine knowledge items, and sources of information, was administered to students in nursing (n = 205), pediatric nursing (n = 46), and midwifery (n = 21). Statistical analyses included descriptive statistics, ANOVA, post hoc tests, and Mann–Whitney U tests. Results: Among the 272 participants, 20.6% reported refusing at least one recommended vaccine, and 18.4% delayed vaccination for non-medical reasons. Vaccine knowledge and confidence increased significantly with academic progression (p < 0.001). Midwifery students showed both the highest concern for long-term vaccine effects and the greatest confidence in vaccine safety. Institutional and scientific sources were the most trusted, though traditional and non-institutional media also influenced perceptions, particularly among midwifery students. Conclusions: Despite high COVID-19 vaccine uptake, VH persists among health professional students. Discipline-specific patterns highlight the need for early, targeted educational strategies to enhance vaccine literacy and reduce hesitancy. Tailored training may empower future professionals to become informed and credible advocates for vaccination.

Vaccines doi: 10.3390/vaccines13080812

Authors: Monika Raethke Jeroen Gorter Rachel Kalf Leontine van Balveren Rana Jajou Florence van Hunsel

Background/Objectives: The aim of this study was to systematically assess Adverse Events Following Immunization (AEFI) among children following administration of the human papillomavirus (HPV) vaccine (Cervarix®) included in the Dutch National Immunization Program (NIP) and to characterize the pattern and recurrence risk of AEFI after HPV revaccination. Methods: A longitudinal cohort event monitoring study, using patient-reported outcomes was used among recipients of the HPV vaccine at 10 years of age. Data were available for 3063 children following the first HPV vaccination and for 2209 children following the second HPV vaccination. Results: The most commonly reported AEFI following HPV vaccination were injection site reactions—reported by 46.5% of participants after the first dose and 31.9% after the second dose—followed by headache (8.2% and 3.9%, respectively) and joint pain (4.5% and 3.7%, respectively). Participants who received both HPV vaccine doses reported more AEFI after the first dose than after the second. Among girls, 61.2% reported at least one AEFI following the first dose, compared to 44.2% after the second dose. For boys, these percentages were 55.3% and 38.5%, respectively. This difference was statistically significant (p = 0.002). For some AEFI, such as injection site reactions, there appears to be a potential increased risk of recurrence following the second dose. Conclusions: This prospective longitudinal cohort event monitoring study showed that AEFI were more frequent after the first HPV dose and more frequent for girls compared to boys. An increased risk of recurrence was seen for AEFI, such as injection site reactions and headache. Furthermore, this study provides insight into the course of AEFI and the extent to which children were affected by these symptoms based on real-world data.

Vaccines doi: 10.3390/vaccines13080811

Authors: Anelisa Jaca Lindi Mathebula Thobile Malinga Kimona Rampersadh Masibulele Zulu Ameer Steven-Jorg Hohlfeld Charles Shey Wiysonge Julie C. Jacobson Vann Duduzile Ndwandwe

Background: Immunization is a highly effective intervention for controlling over 20 life-threatening infectious diseases, significantly reducing both morbidity and mortality rates. One notable achievement in vaccination efforts was the global eradication of smallpox, which the World Health Assembly declared on 8 May 1980. Additionally, there has been a remarkable 99.9% reduction in wild poliovirus cases since 1988, decreasing from more than 350,000 cases that year to just 30 cases in 2022. Objectives: The objective of this review was to assess the effects of various interventions designed to increase vaccination uptake among adults. Search Methods: A thorough search was conducted in the CENTRAL, Embase Ovid, Medline Ovid, PubMed, Web of Science, and Global Index Medicus databases for primary studies. This search was conducted in August 2021 and updated in November 2024. Selection Criteria: Randomized trials were eligible for inclusion in this review, regardless of publication status or language. Data Analysis: Two authors independently screened the search outputs to select potentially eligible studies. Risk ratios (RR) with 95% confidence intervals (CI) were calculated for each randomized controlled trial (RCT). A meta-analysis was conducted using a random-effects model, and the quality of the evidence was assessed using the GRADE approach. Main Results: A total of 35 randomized controlled trials met the inclusion criteria and were included in this review, with the majority conducted in the United States. The interventions targeted adults aged 18 and older who were eligible for vaccination, involving a total of 403,709 participants. The overall pooled results for interventions aimed at increasing influenza vaccination showed a risk ratio of 1.41 (95% CI: 1.15, 1.73). Most studies focused on influenza vaccination (18 studies), while the remaining studies examined various other vaccines, including those for hepatitis A, COVID-19, hepatitis B, pneumococcal disease, tetanus, diphtheria, pertussis (Tdap), herpes zoster, and human papillomavirus (HPV). The results indicate that letter reminders were slightly effective in increasing influenza vaccination uptake compared to the control group (RR: 1.75, 95% CI: 0.97, 1.16; 6 studies; 161,495 participants; low-certainty evidence). Additionally, participants who received education interventions showed increased levels of influenza vaccination uptake compared to those in the control group (RR: 1.88, 95% CI: 0.61, 5.76; 3 studies; 1318 participants; low-certainty evidence). Furthermore, tracking and outreach interventions also led to an increase in influenza vaccination uptake (RR: 1.87, 95% CI: 0.78, 4.46; 2 studies; 33,752 participants; low-certainty evidence). Conclusions: Letter reminders and educational interventions targeted at recipients are effective in increasing vaccination uptake compared to control groups.

Vaccines doi: 10.3390/vaccines13080810

Authors: Weijun Peng Yuan Fang Hongbiao Chen Minjie Zhang Yadi Lin Zixin Wang

Background/Objectives: Chickenpox is an ongoing health threat for young children. This study aimed to investigate varicella vaccination uptake among children and its determinants at both the individual and interpersonal levels. Methods: A cross-sectional survey of parents of children aged 0–15 years and with administrative health records was conducted between September and October 2024 in Shenzhen, China. Participants were recruited through multistage random sampling. This analysis was based on a subsample of 996 parents whose children were 1–10 years old and without a prior history of chickenpox. Multivariate logistic regression models were fitted. Results: Among the participants, 47.0% reported that their children had received a varicella vaccination. Parents who believed that chickenpox was highly contagious (adjusted odds ratios [AOR]: 1.62, 95% confidence interval [CI]: 1.23, 2.13), perceived more benefits (AOR: 1.22, 95% CI: 1.05, 1.41) and cues to action (AOR: 1.33, 95% CI: 1.04, 1.69), and exhibited greater self-efficacy (AOR: 1.40, 95% CI: 1.09, 1.80) related to children’s varicella vaccination reported higher varicella vaccination uptake for their children. Greater perceived barriers related to vaccination (AOR: 0.89, 95% CI: 0.83, 0.95) and dysfunctional interactions with children (AOR: 0.97, 95% CI: 0.94, 0.99) were associated with lower varicella vaccination uptake for children. In addition, higher exposure to information encouraging parents to vaccinate their children against chickenpox (AOR: 1.24, 95%CI: 1.08, 1.41) and thoughtful consideration of the veracity of the information were associated with higher varicella vaccination uptake among children (AOR: 1.19, 95% CI: 1.05, 1.36). Conclusions: There is a strong need to promote varicella vaccination for children in China.

Vaccines doi: 10.3390/vaccines13080809

Authors: Jiaojiao Zhang Zhaomin Feng Ying Shen Weixian Shi Ying Sun Jiachen Zhao Dan Wu Jia Li Chunna Ma Wei Duan Jiaxin Ma Yingying Wang Lu Zhang Xiaodi Hu Quanyi Wang Daitao Zhang Peng Yang

This study aimed to estimate the end-of-season influenza vaccine effectiveness (VE) for the 2024/25 season in Beijing, China. Methods: We used a test-negative design (TND) to assess influenza VE among outpatients with influenza-like illness (ILI) enrolled through the influenza virological surveillance in sentinel hospitals in Beijing from week 44, 2024 to week 14, 2025. Cases were ILI patients who tested positive for influenza; controls were those who tested negative. Results: Among 18,405 ILI patients tested, 3690 (20.0%) were positive for influenza, with A(H1N1)pdm09 as the predominant strain (98.9%). The overall influenza vaccination coverage was 12.4%. Adjusted VE was 48.3% (95%CI: 40.4%–55.3%) against any influenza and 48.2% (95%CI: 40.3%–55.1%) against A(H1N1)pdm09, with the highest VE observed in adults aged 18–59 years (79.0%). The adjusted VE was similar for those vaccinated in 2023/24 only (53.1%) or both 2023/24 and 2024/25 seasons (50.8%), but lower for those vaccinated only in the 2024/25 season (48.5%). The adjusted VE was higher during the epidemic period (52.5%) than in the pre-epidemic (48.1%) and post-epidemic (35.3%) periods. Conclusions: Our findings indicate moderate VE against laboratory-confirmed influenza, especially A(H1N1)pdm09, during the end of the 2024/25 season in Beijing, China. Influenza vaccination provided protective effects across different epidemic periods. These timely estimates support ongoing public health communication and immunization strategies.

Vaccines doi: 10.3390/vaccines13080808

Authors: Young Chan Kim Arturo Reyes-Sandoval

Mosquito-borne viruses such as dengue (DENV), yellow fever (YFV), Zika (ZIKV), and chikungunya (CHIKV) have re-emerged in recent decades, affecting millions of people worldwide [...]

Vaccines doi: 10.3390/vaccines13080807

Authors: Andrea Bongiovanni Giulia Santolini Francesco Vairo Francesco Corea Silvia Aquilani Chiara de Waure

Background: Pneumococcal disease is a significant health burden, particularly among older adults and individuals with chronic conditions. Sequential pneumococcal vaccination (PCV13 followed by PPSV23) has been recommended in Italy since 2017 for its demonstrated efficacy, safety, and cost-effectiveness in preventing invasive pneumococcal disease (IPD). Nevertheless, limited data are available on the sequential pneumococcal vaccination coverage in Italy. This study aimed to evaluate the coverage and trends of sequential pneumococcal vaccination among individuals who turned 65 years old within the Viterbo Local Health Authority between 2018 and 2023. Methods: A retrospective cohort study was conducted using data from the Regional Vaccination Registry (AVR), a comprehensive digital vaccination dataset. Vaccination coverage was calculated based on individuals completing the sequential pneumococcal vaccination within two years after turning 65 years old. Trends as well as subgroup variations based on sex, citizenship, district of residence, and municipality size were analyzed. Results: Among 27,657 individuals who turned 65 years of age during the study period, only 2.32% completed the sequential pneumococcal vaccination. Coverage increased steadily from 2018 (0.60%) to a peak in 2020 (3.27%), followed by a plateau and a decline in 2023 (2.53%). Coverage varied across demographic and geographic subgroups: females (2.58%) had higher coverage than males (2.04%), Italian citizens (2.45%) exceeded foreign residents (0.64%), and residents in District C (3.03%) led over District A (1.08%). Smaller municipalities (≤10,000 inhabitants) showed higher coverage (2.52%) than larger ones (1.98%). Conclusions: Adherence to sequential pneumococcal vaccination has been very low throughout the considered study period. This is highly relevant information to consider in the view of new available pneumococcal vaccines for immunization of the elderly. Furthermore, geographic and demographic differences highlight the need for targeted public health interventions.

Vaccines doi: 10.3390/vaccines13080806

Authors: Laith N. AL-Eitan Diana L. Almahdawi Rabi A. Abu Khiarah Mansour A. Alghamdi

Vaccine equity and access remain critical challenges in global health, particularly in regions with complex socio-political landscapes, like the Middle East. This review examines disparities in vaccine distribution within the Middle Eastern context, analyzing the unique challenges and opportunities across the region. It provides an overview of the area’s diverse finances and its impact on healthcare accessibility. We examine vaccination rates and identify critical barriers to vaccination, which may be particular issues in developing countries, such as vaccine thermostability, logistical hurdles, financial constraints, and socio-cultural factors, or broader problems, like political instability, economic limitations, and deficiencies in healthcare infrastructure. However, we also highlight successful efforts at the regional and national levels to improve vaccine equity, along with their outcomes and impacts. Ultimately, by drawing on the experiences of previous programs and initiatives, we propose strategies to bridge the gaps in vaccine access through sustainable financing, local manufacturing, and the strengthening of health systems. This approach emphasizes the importance of regional collaboration and long-term self-sufficiency in enhancing global health security and achieving more equitable outcomes in the Middle East.

Vaccines doi: 10.3390/vaccines13080805

Authors: Mark H. Rozenbaum Maria J. Tort Blair Capitano Ruth Chapman Desmond Dillon-Murphy Benjamin M. Althouse Alejandro Cane

Background/Objectives: The number needed to vaccinate (NNV) is a metric commonly used to evaluate the public health impact of a vaccine as it represents the number of individuals that must be vaccinated to prevent one case of disease. Traditional calculations may underestimate vaccine benefits by neglecting indirect effects and duration of protection (DOP), resulting in NNV overestimation. This study evaluated the NNV for the pediatric 20-valent pneumococcal conjugate (PCV20) US immunization program, as compared to PCV13, with a unique approach to NNV. Methods: A multi-cohort, population-based Markov model accounting for indirect effects was employed to calculate the NNV of PCV20 to avert a case of pneumococcal disease, invasive pneumococcal disease (IPD), hospitalized non-bacteremic pneumonia (NBP), ambulatory NBP, and otitis media (OM), as well as to prevent antibiotic-resistant cases and antibiotic prescriptions. Results: The mean NNV over a 25-year time horizon to prevent one case of pneumococcal disease was 6, with NNVs of 854 for IPD, 106 for hospitalized NBP, 25 for outpatient NBP, and 9 for OM, 11 for a course of antibiotic, and 4 for resistant disease. The mean NNV per year decreased over time, reflecting the DOP and increasing indirect effects over time. Conclusions: This study presents a novel approach to NNVs and shows that relatively few vaccinations are required to prevent disease. The decrease in NNV over time highlights the necessity of including DOP and indirect effects in NNV calculations, ensuring a more realistic assessment of a vaccine’s impact.

Vaccines doi: 10.3390/vaccines13080804

Authors: Maria Rohova Nikolay L. Mihaylov Antoniya Dimova Rouzha Pancheva

Background/Objectives: Medical and nursing students, as future healthcare professionals, influence public trust and vaccine acceptance. Knowledge gaps or misconceptions regarding immunization may undermine their confidence and effectiveness in addressing vaccine hesitancy. This study explores perceptions and attitudes toward childhood vaccination among Bulgarian healthcare students and factors shaping these outcomes. Methods: A cross-sectional survey was conducted in 2024, using an online self-administered questionnaire completed by 374 medical and nursing students. Descriptive statistics were used to analyze vaccine-related responses, comparing attitudes between healthcare programs and education years. Binomial logistic regression was applied to identify predictors of support for mandatory vaccination, first considering demographic and academic variables, and then adding students’ beliefs and common misconceptions. Results: Medical students showed more positive attitudes toward vaccination than nursing students, with 96.8% of medical students versus 89.4% of nursing students believing vaccines are effective (p = 0.005). Students in advanced years demonstrated stronger belief in vaccine effectiveness (p = 0.038). Additionally, misbeliefs about the measles vaccine causing autism decreased significantly, with most students in higher years rejecting this misconception (p = 0.009). Logistic regression revealed that belief in following the vaccine schedule (OR = 22.71; p < 0.001) and confidence in vaccine effectiveness (OR = 10.20; p < 0.001) were the strongest predictors of support for mandatory vaccination, with attitudinal factors explaining over half of the variance. Conclusions: Healthcare students’ attitudes about vaccination influence public health outcomes, as their perspectives reflect experience and beliefs. Targeted vaccine education helps address misconceptions and improve vaccination rates.

Vaccines doi: 10.3390/vaccines13080803

Authors: Liani Coronado àlex Cobos Adriana Mu?oz-Aguilera Sara Puente-Marin Gemma Guevara Cristina Riquelme Saray Heredia Manuel V. Borca Llilianne Ganges

Background/Objectives: Classical swine fever (CSF) continues to challenge global eradication efforts, particularly in endemic regions, where pregnant sows face heightened risks of vertical transmission following exposure to CSFV. Methods: This study evaluates the early protective efficacy of FlagT4G, a novel live attenuated DIVA-compatible vaccine. Pregnant sows were vaccinated at mid-gestation and challenged 14 days later with a highly virulent CSFV strain. Results: FlagT4G conferred complete clinical protection, preventing both maternal viremia and transplacental transmission. No CSFV RNA, specific antibodies, or IFN-α were detected in fetal samples from vaccinated animals. In contrast, unvaccinated sows exhibited clinical signs, high viral loads, and widespread fetal infection. Interestingly, early protection was observed even in the absence of strong humoral responses in some vaccinated sows, suggesting a potential role for innate or T-cell-mediated immunity in conferring rapid protection. Conclusions: The demonstrated efficacy of FlagT4G within two weeks of vaccination underscores its feasibility for integration into emergency vaccination programs. Its DIVA compatibility and ability to induce early fetal protection against highly virulent CSFV strains position it as a promising tool for CSF control and eradication strategies.

Vaccines doi: 10.3390/vaccines13080802

Authors: Ting Xiong Yanfen Lyu Hongmei Li Ting Xu Shuting Wu Zekun Yang Mengyao Jing Fei Xu Dingxiang Liu Ruiai Chen

Background: Infectious bronchitis virus (IBV) is a gammacoronavirus that causes a highly contagious disease in chickens and seriously endangers the poultry industry. The GI-19 is a predominant lineage. However, no effective commercially available vaccines against this virus are available. Methods: In this present study, the CHO eukaryotic and the E.coli prokaryotic expression system were used to express S1-SpyTag and AP205-SpyCatcher, respectively. Subsequently, the purified S1-SpyTag and AP205-SpyCatcher were coupled to form the nanoparticles AP205-S1 (nAP205-S1) in PBS buffer at 4 °C for 48 h. S1-SpyTag and nAP205-S1 were formulated into vaccines with white oil adjuvant and employed to immunize 1-day-old SPF chickens for the comparative evaluation of their immune efficacy. Results: The nAP205-S1 vaccine in chickens induced robust IBV-specific humoral and cellular immune responses in vivo. Importantly, the humoral and cellular immune responses elicited by the nAP205-S1 vaccine were more robust than those induced by the IBV S1-SpyTag vaccine at both the same dose and double the dose, with a notably significant difference observed in the cellular immune response. Furthermore, experimental data revealed that chicken flocks vaccinated with nAP205-S1 achieved 100% group protection following a challenge, exhibiting a potent protective immune response and effectively inhibiting viral shedding. Conclusions: These results reveal the potential of developing a novel nanoparticle vaccine with broadly protective immunity against GI-19 IBV.

Vaccines doi: 10.3390/vaccines13080801

Authors: Long Cheng Denglong Xie Wei Ji Xiaohong Ye Fangheng Yu Xiaohui Yang Nan Gao Yan Zhang Shu Zhu Yongqi Zhou

Background/Objectives: Porcine circovirus type 2 (PCV2) infection causes porcine circovirus disease (PCVD), a global immunosuppressive disease in pigs. Its clinical manifestations include post-weaning multisystemic wasting syndrome (PMWS) and porcine dermatitis and nephropathy syndrome (PDNS), which cause significant economic losses to the swine industry. The Cap protein, which is the major protective antigen of PCV2, can self-assemble to form virus-like particles (VLPs) in the insect baculovirus expression system. Few studies have compared the expression of Cap proteins in different baculovirus expression systems. Methods: In this study, we compared two commonly commercialized baculovirus construction systems with the Cap protein expression in various insect cells. Results: The results demonstrate that the flashBAC system expressed the Cap protein at higher levels than the Bac-to-Bac system. Notably, when expressing four copies of the Cap protein, the flashBAC system achieved the highest protein yield in High Five cells, where it reached 432 μg/mL at 5 days post-infection (dpi) with 27 °C cultivation. Animal experiments confirmed that the purified Cap protein effectively induced specific antibody production in mice and swine. Conclusions: This study provides critical data for optimizing the production of the PCV2 Cap protein, which is of great significance for reducing the production cost of PCV2 vaccines and improving the industrial production efficiency.

Vaccines doi: 10.3390/vaccines13080800

Authors: Huibin Yu Mary Eloise L. Fernandez Chen Peng Dewi Megawati Greg Brennan Loubna Tazi Stefan Rothenburg

Background: Protein kinase R (PKR) inhibits general mRNA translation by phosphorylating the alpha subunit of eukaryotic translation initiation factor 2 (eIF2). PKR also modulates NF-κB signaling during viral infections, but comparative studies of PKR-mediated NF-κB responses across mammalian species and their regulation by viral inhibitors remain largely unexplored. This study aimed to characterize the conserved antiviral and inflammatory roles of mammalian PKR orthologs and investigate their modulation by poxviral inhibitors. Methods: Using reporter gene assays and quantitative RT-PCR, we assessed the impact of 17 mammalian PKR orthologs on general translation inhibition, stress-responsive translation, and NF-κB-dependent induction of target genes. Congenic human and rabbit cell lines infected with a myxoma virus strain lacking PKR inhibitors were used to compare the effects of human and rabbit PKR on viral replication and inflammatory responses. Site-directed mutagenesis was employed to determine key residues responsible for differential sensitivity to the viral inhibitor M156. Results: All 17 mammalian PKR orthologs significantly inhibited general translation, strongly activated stress-responsive ATF4 translation, and robustly induced NF-κB target genes. Inhibition of these responses was specifically mediated by poxviral K3 orthologs that effectively suppressed PKR activation. Comparative analyses showed human and rabbit PKRs similarly inhibited virus replication and induced cytokine transcripts. Amino acid swaps between rabbit PKRs reversed their sensitivity to viral inhibitor M156 and NF-κB activation. Conclusions: Our data show that the tested PKR orthologs exhibit conserved dual antiviral and inflammatory regulatory roles, which can be antagonized by poxviral K3 orthologs that exploit eIF2α mimicry to modulate the PKR-NF-κB axis.

Vaccines doi: 10.3390/vaccines13080799

Authors: Martina Bozhkova Ralitsa Raycheva Steliyan Petrov Dobrina Dudova Teodora Kalfova Marianna Murdjeva Hristo Taskov Velizar Shivarov

Background: Understanding the duration and quality of immune memory following SARS-CoV-2 infection and vaccination is critical for informing public health strategies and vaccine development. While waning antibody levels have raised concerns about long-term protection, the persistence of memory B cells (MBCs) and T cells plays a vital role in sustaining immunity. Materials and Methods: We conducted a longitudinal prospective study over 12 months, enrolling 285 participants in total, either after natural infection or vaccination with BNT162b2 or mRNA-1273. Peripheral blood samples were collected at four defined time points (baseline, 1–2 months, 6–7 months, and 12–13 months after vaccination or disease onset). Immune responses were assessed through serological assays quantifying anti-RBD IgG and neutralizing antibodies, B-ELISPOT, and multiparameter flow cytometry for S1-specific memory B cells. Results: Both mRNA vaccines induced robust B cell and antibody responses, exceeding those observed after natural infection. Memory B cell frequencies peaked at 6 months and declined by 12 months, but remained above the baseline. The mRNA-1273 vaccine elicited stronger and more durable humoral and memory B-cell-mediated immunity compared to BNT162b2, likely influenced by its higher mRNA dose and longer prime-boost interval. Class-switched memory B cells and S1-specific B cells were significantly expanded in vaccine recipients. Natural infection induced more heterogeneous immune memory. Conclusions: Both mRNA vaccination and natural SARS-CoV-2 infection induce a comparable expansion of memory B cell subsets, reflecting a consistent pattern of humoral immune responses across all studied groups. These findings highlight the importance of vaccination in generating sustained immunological memory and suggest that the vaccine platform and dosage influence the magnitude and durability of immune responses against SARS-CoV-2.

Vaccines doi: 10.3390/vaccines13080798

Authors: Lina M. Würfel Anja Potthoff Adriane Skaletz-Rorowski Sandeep Nambiar Nessr Abu Rached

Human immunodeficiency virus (HIV) infection remains a major challenge in global health. In recent years, vaccines have emerged as an important tool for the treatment and prevention of HIV-related complications. This review article addresses the evolving landscape of vaccines for people living with HIV (PLWH), evaluating current vaccination strategies for standard vaccines and travel vaccines in PLWH compared to the general population and offering a summary of the current recommended vaccines. It evaluates studies for vaccine effectiveness and safety and discusses methods to improve vaccination rates among PLWH. Systematic research was carried out using keywords. We address the current state of knowledge and highlight areas for future research and development.

Vaccines doi: 10.3390/vaccines13080797

Authors: Jiho Kim Jenn Davis Bryan Berube Malcolm Duthie Sean A. Gray Darrick Carter

Background/Objectives: mRNA vaccines introduced during the COVID-19 pandemic were a significant step forward in the rapid development and deployment of vaccines in a global pandemic context. These vaccines showed good protective efficacy, but—due to limited breadth of the immune response—they required frequent boosters with manufactured spike sequences that often lagged behind the circulating strains. In order to enhance the breadth, durability, and magnitude of immune responses, we studied the effect of combining priming with an RNA vaccine technology with boosting with protein/adjuvant using a TLR4-agonist based adjuvant. Methods: Specifically, four proprietary adjuvants (EmT4TM, LiT4QTM, MiT4TM, and AlT4TM) were investigated in combination with multiple modes of SARS-CoV-2 vaccination (protein, peptide, RNA) for their effectiveness in boosting antibody responses to SARS-CoV-2 spike protein in murine models. Results: Results showed significant improvement in immune response strength and breadth—especially against more distant SARS-CoV-2 variants such as Omicron—when adjuvants were used in combination with boosters following an RNA vaccine prime. Conclusions: The use of novel TLR4 adjuvants in combination with protein or RNA vaccinations presents a promising strategy for improving the efficacy of vaccines in the event of future pandemics, by leveraging rapid response using an RNA vaccine prime and following up with protein/adjuvant-based vaccines to enhance the breadth of immunity.

Vaccines doi: 10.3390/vaccines13080796

Authors: Abiu Sempere Natalia Egri Angela Gonzalez Ibai Los-Arcos María Angeles Marcos Javier Bernal-Maurandi Diana Ruiz-Cabrera Fritz Dieckmann Francesc Moreso Néstor Toapanta Mariona Pascal Marta Bodro

Background: BK polyomavirus (BKPyV) reactivation is a common complication after kidney transplantation and may result in nephropathy and graft loss. As there is no effective antiviral therapy, management focuses on early detection and reduction of immunosuppression, which increases the risk of rejection. Identifying patients at higher risk remains challenging. Monitoring BKPyV-specific T-cell responses could aid in predicting reactivation. This study evaluated the usefulness of ELISpot to monitor BKPyV-specific cellular immunity before and after kidney transplantation. Methods: A prospective multicenter study was conducted between October 2020 and March 2022. ELISpot assays were performed prior to transplantation and two months afterward. Results: Seventy-two patients were included, with a median age of 56 years; 61% were men, and 24% had undergone previous transplantation. Nine patients developed presumptive BKPyV-nephropathy. No significant differences were found in donor type, induction therapy, or rejection rates between patients with or without nephropathy (p = 0.38). Based on ELISpot results, patients were classified into three groups according to their risk of BKPyV-nephropathy. The high-risk group included those who changed from positive to negative at 2 months post-transplant, representing 40% of presumptive BKPyV-nephropathy cases. Patients who remained negative at 2 months were classified as moderate risk (14.5%), while those with a positive ELISpot at 2 months comprised the low-risk group (0%). In the logistic regression analysis, both the ELISpot risk category [OR 19 (CI 1.7–2.08)] and the use of mTOR inhibitors from the start of transplantation [OR 0.02 (CI 0.01–0.46)] were significantly associated with BKPyV-nephropathy. Conclusions: Monitoring BKPyV-specific T cells with ELISpot before and after kidney transplantation may help stratify patients by risk of reactivation. Loss of BKPyV immunity at two months is associated with nephropathy, while mTOR-based immunosuppression appears protective. This strategy could guide personalized immunosuppression and surveillance.

Vaccines doi: 10.3390/vaccines13080795

Authors: Nannan Jia Lin Ai Yunping Ma Chen Hua Qi Shen Chen Wang Teng Li Yingdan Wang Yunyi Li Yin Yang Chi Zhou Min Chen Huanyu Wu Xin Chen Lu Lu Yanqiu Zhou Jinghe Huang Fan Wu

Objectives: Understanding the antibody response in monkeypox virus (MPXV)-infected and uninfected individuals is essential for developing next-generation MPXV vaccines. This study aimed to characterize neutralizing antibody (NAb) and antibody-dependent cellular cytotoxicity (ADCC) responses in both groups, providing insights into immune protection and vaccine design. Methods: A recombinant vaccinia Tian Tan (VTT) virus was utilized to develop high-throughput luciferase-reporter-based neutralization and ADCC assays. These assays were applied to evaluate the presence and levels of poxvirus-specific antibodies in MPXV-infected and uninfected individuals, including those vaccinated with vaccinia-based vaccines. Results: Poxvirus-specific NAbs were detected in MPXV-negative individuals with prior vaccinia vaccination. However, MSM individuals exhibited significantly lower pre-existing NAb levels than non-MSM individuals, potentially contributing to their higher susceptibility to MPXV infection. In individuals with mild MPXV infection, robust NAb and ADCC responses were observed, regardless of vaccination status. Additionally, HIV-positive individuals demonstrated comparable antibody responses following MPXV infection. Conclusions: These findings highlight the potential role of pre-existing NAbs in MPXV susceptibility and the strong immune response elicited by mild MPXV infection. Further research is needed to determine whether MPXV-specific antibodies mitigate disease progression, which could inform the development of effective MPXV vaccines.

Vaccines doi: 10.3390/vaccines13080794

Authors: Luciano Ettorre Trevor Williams Camille Houy Shaolong Zhu Michael Kishko Ali Azizi Andrew D. James Beata Gajewska Jason Szeto

Background/Objectives: An initial COVID-19 candidate vaccine containing a purified ancestral SARS-CoV-2 spike antigen was characterized with an ELISA using recombinant monoclonal antibodies (mAbs) generated against this variant. Upon the emergence of a new Beta (B.1.351) spike variant early in the pandemic, the assessment of a bivalent vaccine containing ancestral and Beta spike antigens began. Due to accelerated project timelines, mAbs generated specifically against the Beta spike antigen were not available at the time to address assay development and vaccine testing requirements. Methods: Using only the initial mAb panel raised against the ancestral spike antigen, an epitope-blocking ELISA strategy was developed to independently measure Beta spike antigen in bivalent vaccine formulations. To facilitate this, epitope profiling of spike antigens from both ancestral and Beta variants was performed with biolayer interferometry and hydrogen–deuterium exchange mass spectrometry using the original panel of mAbs. Results: The resulting blocking ELISA was precise and specific for the Beta spike antigen and detected the expected amount of this antigen in bivalent vaccine formulations. The specific amount of ancestral spike protein in the bivalent vaccine was also confirmed using the original ELISA developed at the onset of the pandemic. Conclusions: This epitope-blocking strategy helped to overcome key reagent availability issues and could be applied to other projects involving related proteins.

Vaccines doi: 10.3390/vaccines13080793

Authors: Ramin Sabet-Azad Catherine Hoath Nicole Bézay Anna S?rnef?lt

Rapid vaccine availability is essential for effective epidemic and pandemic response. Building on the Coalition for Epidemic Preparedness Innovations (CEPI) 100 Days Mission, which aims to have new vaccines ready for initial authorization and manufacturing at scale within 100 days of recognition of a pandemic pathogen, the CEPI has developed a Chemistry, Manufacturing and Controls (CMC) Rapid Response Framework to define technical and logistical CMC requirements to enable rapid vaccine availability. Central to this framework is the availability of adaptable vaccine platforms that can be readily tailored to emerging pathogens. To support strategic decision-making and identify gaps in platform capabilities, CEPI has created the Platform Readiness Dashboard. This tool provides a structured, multi-dimensional initial assessment of platform maturity across six key categories: Adaptability, Compatibility, Suitability, Regulatory, Manufacturing, and Facility Readiness. Each category includes specific technical and operational considerations scored using a color-coded system to reflect outbreak response readiness level. This Dashboard aims to enable vaccine developers, manufacturers, funders, and outbreak response teams to evaluate platform strengths and limitations at any given time, informing funding, preparedness and response activities. By offering a dynamic view of essential platform readiness indicators, the dashboard can communicate progress supporting faster responses to future health emergencies.

Vaccines doi: 10.3390/vaccines13080792

Authors: Essie Komla Erwin G. Abucayon C. Steven Godin Agnieszka Sulima Arthur E. Jacobson Kenner C. Rice Gary R. Matyas

Background/Objectives: Opioid use disorder (OUD) remains a severe health problem globally, resulting in substantial social and economic challenges. While existing medications for managing OUD are proven to be effective, they also present certain challenges. A vaccine offers a promising therapeutic strategy to combat OUD and potentially reduce the risk of overdose death. The TT-6-AmHap heroin conjugate vaccine has effectively reduced heroin-induced pharmacological effects in behavioral assays as well as demonstrated the induction of high titer and high affinity antibody responses in mice and rats. In this GLP study conducted in rabbits, the potential local and systemic toxicity of the TT-6-AmHap heroin vaccine in combination with or without adjuvants ALF43 and Alhydrogel® (ALFA) was investigated. Methods: Male and female New Zealand White rabbits were administered with vaccines or a saline control intramuscularly at two-week intervals over a 57-day study period. The presence, persistence or reversibility of any toxic effects of the vaccine was determined over a four-week recovery period. Results: Administration of TT-6-AmHap with or without the adjuvants induced high antibody-specific IgG in treatment groups compared to the controls. The study found no TT-6-AmHap-related effects on mortality, physical examinations, dermal Draize observations, body weights, body weight changes, food consumption, ophthalmology, clinical pathology (hematology, coagulation, clinical chemistry, and urinalysis), macroscopic pathology, or organ weights. Conclusions: Under the conditions of this study, these results demonstrate that the TT-6-AmHap vaccine with or without adjuvants was well tolerated, immunogenic, and the effects were not considered adverse in both male and female rabbits.

Vaccines doi: 10.3390/vaccines13080791

Authors: Sara Boccalini Veronica Gironi Primo Buscemi Paolo Bonanni Barbara Muzii Salvatore Parisi Marta Borchiellini Angela Bechini

Introduction: Respiratory Syncytial Virus (RSV) is the leading cause of lower respiratory tract infections in infants and children, as well as hospitalizations for respiratory infections in the pediatric population, representing a significant public health concern. Nirsevimab, a long-acting anti-RSV monoclonal antibody, has recently been approved by the European Medicines Agency (EMA). The aim of this study is to assess the utility of certain parameters, such as the Number Needed to Immunize (NNI), in supporting decision-makers regarding the introduction of nirsevimab as a universal prophylactic measure. Methods: A literature review was conducted to identify the definition and application of the NNI in the context of infectious disease prevention. The following online databases were consulted: Scopus, MEDLINE, Google Scholar, Web of Science, and Cochrane Library. The search was restricted to English-language texts published between 1 January 2000 and 30 January 2025. Results: The NNI represents the number of individuals who need to be immunized to prevent clinical outcomes such as medical visits and hospitalizations caused by infectious diseases. Six studies were identified that utilized this parameter to outline the benefits of immunization and describe the advantages of using monoclonal antibodies for RSV disease. Finelli and colleagues report that to prevent one RSV-related hospitalization, 37–85 infants aged 0–5 months and 107–280 infants aged 6–11 months would need to be immunized with long-acting anti-RSV antibodies. A recent study by Mallah et al. on the efficacy of nirsevimab estimates that the NNI required to prevent one RSV-related hospitalization is 25 infants. Studies by Francisco and O’Leary report NNI values of 82 and 128 infants, respectively, to prevent one RSV-related hospitalization with nirsevimab. Mallah et al. describe NNI as a metric useful to quantify the immunization effort needed to prevent a single RSV hospitalization. A recent Italian study reports that 35 infants need to be immunized to prevent one hospitalization due to RSV-LRTI and 3 infants need to be immunized to prevent one primary care visit due to RSV-LRTI. The studies indicate that the NNI for anti-RSV monoclonal antibodies is lower than the corresponding Number Needed to Vaccinate (NNV) for vaccines already included in national immunization programs. The main limitations of using this parameter include the absence of a shared threshold for interpreting results and the lack of consideration for the indirect effects of immunization on the population. Conclusions: The NNI is an easily understandable tool that can be used to convey the value of an immunization intervention to a variety of stakeholders, thereby supporting public health decision-making processes when considered in association with the uptake of the preventative strategy. At the current status, the estimated NNI of monoclonal antibodies against RSV results favourable and confirms the use in the first year of life for the prevention of RSV disease.

Vaccines doi: 10.3390/vaccines13080790

Authors: Muhammad Bakhsh Amal Senevirathne Jamal Riaz Jun Kwon Ram Prasad Aganja Jaime C. Cabarles Sang-Ik Oh John Hwa Lee

Background: Fowl typhoid (FT), a septicemic infection caused by Salmonella Gallinarum (SG), and H9N2 avian influenza are two economically important diseases that significantly affect the global poultry industry. Methods: We exploited the live attenuated Salmonella Gallinarum (SG) mutant JOL3062 (SG: ∆lon ∆pagL ∆asd) as a delivery system for H9N2 antigens to induce an immunoprotective response against both H9N2 and FT. To enhance immune protection against H9N2, a prokaryotic and eukaryotic dual expression plasmid, pJHL270, was employed. The hemagglutinin (HA) consensus sequence from South Korean avian influenza A virus (AIV) was cloned under the Ptrc promoter for prokaryotic expression, and the B cell epitope of neuraminidase (NA) linked with matrix protein 2 (M2e) was placed for eukaryotic expression. In vitro and in vivo expressions of the H9N2 antigens were validated by qRT-PCR and Western blot, respectively. Results: Oral immunization with JOL3121 induced a significant increase in SG and H9N2-specific serum IgY and cloacal swab IgA antibodies, confirming humoral and mucosal immune responses. Furthermore, FACS analysis showed increased CD4+ and CD8+ T cell populations. On day 28 post-immunization, there was a substantial rise in the hemagglutination inhibition titer in the immunized birds, demonstrating neutralization capabilities of immunization. Both IFN-γ and IL-4 demonstrated a significant increase, indicating a balance of Th1 and Th2 responses. Intranasal challenge with the H9N2 Y280 strain resulted in minimal to no clinical signs with significantly lower lung viral titer in the JOL3121 group. Upon SG wildtype challenge, the immunized birds in the JOL3121 group yielded 20% mortality, while 80% mortality was recorded in the PBS control group. Additionally, bacterial load in the spleen and liver was significantly lower in the immunized birds. Conclusions: The current vaccine model, designed with a host-specific pathogen, SG, delivers a robust immune boost that could enhance dual protection against FT and H9N2 infection, both being significant diseases in poultry, as well as ensure public health.

Vaccines doi: 10.3390/vaccines13080789

Authors: Alexander A. Soldatov Nickolay A. Kryuchkov Dmitry V. Gorenkov Zhanna I. Avdeeva Oxana A. Svitich Sergey Soshnikov

The COVID-19 pandemic accelerated the rapid development and distribution of various vaccine platforms, resulting in a significant reduction in disease severity, hospitalizations, and mortality. However, persistent challenges remain concerning the durability and breadth of vaccine-induced protection, especially in the face of emerging SARS-CoV-2 variants. This review aimed to evaluate the factors influencing the immunogenicity and effectiveness of COVID-19 vaccines to inform future vaccine advancement strategies. A narrative review with systematic approach was conducted following PRISMA guidelines for narrative review. Literature was sourced from databases including PubMed, Embase, and Web of Science for studies published between December 2019 and May 2025. Encompassed studies assessed vaccine efficacy, immunogenicity, and safety across various populations and vaccine platforms. Data were collected qualitatively, with quantitative data from reviews highlighted where available. We have uncovered a decline in vaccine efficacy over time and weakened protection against novel variants such as Delta and Omicron. Booster doses, specifically heterologous regimens, improved immunogenicity and increased protection. Vaccine-induced neutralizing antibody titers have been found to correlate with clinical protection, although the long-term correlates of immunity remain poorly defined. The induction of IgG4 antibodies after repeated mRNA vaccinations raised concerns about potential modulation of the immune response. COVID-19 vaccines have contributed significantly to pandemic control; however, their efficacy is limited by the evolution of the virus and declining immunity. Forthcoming vaccine strategies should focus on broad-spectrum, variant-adapted formulations and defining robust comparisons of protection. Recognizing the immunological basis of vaccine response, including the role of specific antibody subclasses, is fundamental for optimizing long-term protection.

Vaccines doi: 10.3390/vaccines13080788

Authors: Majed Ghattas Garima Dwivedi Anik Chevrier Trevor Scobey Rakan El-Mayta Melissa D. Mattocks Dong Wang Marc Lavertu Mohamad-Gabriel Alameh

Background: Chitosan, a family of polysaccharides composed of glucosamine and N-acetyl glucosamine, is a promising adjuvant candidate for eliciting potent immune response. Methods: This study compared the adjuvant effects of chitosan to those of empty lipid nanoparticles (eLNPs) and aluminum hydroxide (alum) following administration of recombinant SARS-CoV-2 spike immunogen in adult mice. Mice received the adjuvanted recombinant protein vaccine in a prime-boost regimen with four weeks interval. Subsequent analyses included serological assessment of antibody responses, evaluation of T cell activity, immune cell recruitment and cytokine profiles at injection site. Results: Compared to alum, chitosan induced a more balanced Th1/Th2 response, akin to that observed with eLNPs, demonstrating its ability to modulate both the humoral and cellular immune pathways. Chitosan induced a different proinflammatory cytokine (e.g., IL-1⍺, IL-2, IL-6, and IL-7) and chemokine (e.g., Eotaxin, IP-10, MIP-1a) profile compared to eLNPs and alum at the injection site and in the draining lymph nodes. Moreover, chitosan potentiated the recruitment of innate immune cells, with neutrophils accounting for about 40% of the infiltrating cells in the muscle, representing a ~10-fold increase compared to alum and a comparable level to eLNPs. Conclusions: These findings collectively indicate that chitosan has the potential to serve as an effective adjuvant, offering comparable, and potentially superior, properties to those of currently approved adjuvants.

Vaccines doi: 10.3390/vaccines13080787

Authors: Su In Heo Hae-Ji Kang Jie Mao Zhao-Shou Yang Md Atique Ahmed Fu-Shi Quan

Background: Toxoplasma gondii (T. gondii) causes severe disease in immunocompromised individuals and pregnant women, underscoring the urgent need for effective vaccines against toxoplasmosis. The dense granule protein 5 (GRA5) of T. gondii plays a key role in parasitic cyst formation. Methods: This study evaluated the protective immune responses induced by a virus-like particle (VLP) vaccine expressing the T. gondii-derived antigen GRA5 in a mouse model challenged with the ME49 strain of T. gondii. GRA5 VLPs were generated using a baculovirus expression system, and VLP formation was confirmed by Western blotting and visualized using transmission electron microscopy. Mice were intranasally immunized with GRA5 VLPs three times at 4-week intervals to induce immune responses, followed by infection with T. gondii ME49. Results: Intranasal immunization with GRA5 VLPs induced parasite-specific IgG antibody responses in the serum and both IgG and IgA antibody responses in the brain. Compared to the non-immunized group, immunized mice exhibited significantly higher levels of germinal center B cells and antibody-secreting cell responses. Moreover, the VLP vaccine suppressed the production of IFN-γ and IL-6 cytokines, leading to a significant reduction in brain inflammation and decreased cyst counts following lethal challenge with T. gondii ME49 infection. Conclusion: These findings suggest that the GRA5 VLP vaccine derived from T. gondii elicits a protective immune response, highlighting its potential as an effective vaccine candidate against toxoplasmosis.

Vaccines doi: 10.3390/vaccines13080786

Authors: Kexin Cao Yiu-Wing Kam

Cervical cancer remains a significant global public health challenge, with human papillomavirus (HPV) as its primary cause. In response, the World Health Organization (WHO) launched a global strategy to eliminate cervical cancer by 2030 and, in its 2022 position paper, recommended a single-dose vaccination schedule. The objective of this review is to critically examine the current HPV vaccination landscape in China, including vaccination policies, immunization schedules, supply–demand dynamics, and the feasibility of transitioning to a single-dose regimen. By synthesizing recent developments in HPV virology, epidemiology, vaccine types, and immunization strategies, we identify both opportunities and barriers unique to the Chinese context. Results indicate that China primarily adheres to a three-dose vaccination schedule, with an optional two-dose schedule for girls aged 9–14, leaving a notable gap compared to the most recent WHO recommendation. The high prevalence of HPV types 52 and 58 contributes to a distinct regional infection pattern, underscoring the specific need for nine-valent vaccines tailored to China’s epidemiological profile. Despite the growing demand, vaccine supply remains inadequate, with an estimated annual shortfall of more than 15 million doses. This issue is further complicated by strong public preference for the nine-valent vaccine and the relatively high cost of vaccination. Emerging evidence supports the comparable efficacy and durable protection of a single-dose schedule, which could substantially reduce financial and logistical burdens while expanding coverage. This review advocates for the adoption of a simplified single-dose regimen, supported by catch-up strategies for older cohorts and the integration of HPV vaccination into China’s National Immunization Program (NIP). Sustained investment in domestic vaccine development and centralized procurement of imported vaccines may also possibly alleviate supply shortage. These coordinated efforts are critical for strengthening HPV-related disease prevention and accelerating China’s progress toward the WHO’s cervical cancer elimination targets.

Vaccines doi: 10.3390/vaccines13080785

Authors: Ariane Nardy Fernanda Rodrigues Monteiro Brenda Rodrigues Silva J?natas Bussador do Amaral Danielle Bruna Leal Oliveira érika Donizetti de Oliveira Candido Edison Luiz Durigon Andressa Sim?es Aguiar Guilherme Pereira Scagion Vanessa Nascimento Chalup Guilherme Eustáquio Furtado Marina Tiemi Shio Carolina Nunes Fran?a Luiz Henrique da Silva Nali André Luis Lacerda Bachi

Background: Chronic cytomegalovirus (CMV) infection may favor the development of immunosenescence and inflammation that impair vaccine responses, including COVID-19. In addition, the polymorphism of the interferon-lambda gene (IFNλ) affects COVID-19 immune responses in older adults. Objective: We aimed to investigate the impact of IFNλ polymorphism (IL28B gene-rs12979860) on the immune/inflammatory response to vaccination with CoronaVac for COVID-19 in older adults who were CMV-seropositive. Methods: Blood samples from 42 CMV-seropositive older adults (73.7 ± 4.5 years) were collected before and 30 days after immunization with a second dose of the CoronaVac vaccine to evaluate the immune/inflammatory response. Results: At genotyping, 20 subjects were homozygous for the C/C alleles (Allele-1 group), 5 were homozygous for the T/T Alleles (Allele-2 group), and 17 were heterozygous (C/T, Alleles-1/2 group). The Allele-1 group showed higher IgG levels for COVID-19 (p = 0.0269) and intermediate monocyte percentage (p = 0.017), in contrast to a lower non-classical monocyte percentage (p = 0.0141) post-vaccination than pre-vaccination. Also, this group showed that IgG levels for CMV were positively associated with a systemic pro-inflammatory state and senescent T cells (CD4+ and CD8+). The Allele-2 group presented higher IFN-β levels at pre- (p = 0.0248) and post-vaccination (p = 0.0206) than the values in the Allele-1 and Alleles-1/2 groups, respectively. In addition, the Allele-2 and Alleles-1/2 groups showed that IgG levels for COVID-19 were positively associated with a balanced systemic inflammatory state. Conclusion: CMV-seropositivity in older adults who had Allele-1 could lead to an unbalanced systemic inflammatory state, which may impair their antibody response to COVID-19 vaccination compared to other volunteer groups.

Vaccines doi: 10.3390/vaccines13080784

Authors: Jessica Presa Eva Jodar Monica Ochapa Tim A. Mullenix Sharon E. Barrett Alejandro Cane

In the United States, adolescents and young adults between the ages of 16 and 23 have high rates of serogroup B meningococcal infections due to an elevated risk for those attending college. This review examines meningococcal vaccination requirements and recommendations for college students in the United States, with a focus on state-level mandates. National stakeholder resources, state legislatures, and official state Department of Health and Department of Education websites were analyzed for each state and Washington, DC. Overall, 26 states mandate MenACWY vaccination for college entry, whereas only 2 have specific requirements for MenB vaccination. Among the six states with the largest state university campus enrollments, half mandate MenACWY vaccination for college students, whereas none mandate MenB. By region, the Northeast had the highest percentage of states with a MenACWY requirement for college entry (77.8%) followed by the South (64.7%), Midwest (41.7%), and West (23.1%). Further research is needed to elucidate the relationship between state mandates and coverage to aid in optimizing meningococcal vaccination for college students.

Vaccines doi: 10.3390/vaccines13080783

Authors: Ao Zhang Bin Tan Jiahui Wang Shuqin Zhang

Background/Objectives: Swine influenza A virus (swIAV), a prevalent respiratory pathogen in porcine populations, poses substantial economic losses to global livestock industries and represents a potential threat to public health security. Neuraminidase (NA) has been proposed as an important component for universal influenza vaccine development. NA has potential advantages as a vaccine antigen in providing cross-protection, with specific antibodies that have a broad binding capacity for heterologous viruses. In this study, we evaluated the immunogenicity and protective efficacy of a tetrameric recombinant NA subunit vaccine in a swine model. Methods: We constructed and expressed structurally stable soluble tetrameric recombinant NA (rNA) and prepared subunit vaccines by mixing with ISA 201 VG adjuvant. The protective efficacy of rNA-ISA 201 VG was compared to that of a commercial whole inactivated virus vaccine. Pigs received a prime-boost immunization (14-day interval) followed by homologous viral challenge 14 days post-boost. Results: Both rNA-ISA 201 VG and commercial vaccine stimulated robust humoral responses. Notably, the commercial vaccine group exhibited high viral-binding antibody titers but very weak NA-specific antibodies, whereas rNA-ISA 201 VG immunization elicited high NA-specific antibody titers alongside substantial viral-binding antibodies. Post-challenge, both immunization with rNA-ISA 201 VG and the commercial vaccine were effective in inhibiting viral replication, reducing viral load in porcine respiratory tissues, and effectively mitigating virus-induced histopathological damage, as compared to the PBS negative control. Conclusions: These findings found that the anti-NA immune response generated by rNA-ISA 201 VG vaccination provided protection comparable to that of a commercial inactivated vaccine that primarily induces an anti-HA response. Given that the data are derived from one pig per group, there is a requisite to increase the sample size for more in-depth validation. This work establishes a novel strategy for developing next-generation SIV subunit vaccines leveraging NA as a key immunogen.

Vaccines doi: 10.3390/vaccines13080782

Authors: Jing Yu Huihui Li Yuying Ji Hailan Liao

The varicella-zoster virus is a human herpesvirus that causes varicella as the primary infection and HZ as the reactivation of a latent infection. Ten to twenty percent of cases of herpes zoster ophthalmicus (HZO) involve the ophthalmic branch of the fifth cranial nerve. Any area of the eye may be affected by the condition. HZ has a lifetime risk of more than 30%. Complications from herpes zoster can significantly lower quality of life. The goal of HZ vaccinations is to stop HZ activation and PHN formation. Despite the uncommon possibility of side effects such as eye problems, the majority of vaccines on the market now are safe. The purpose of this review is to discuss VZV infection and analyze and summarize the ocular complications following VZV vaccination.

Vaccines doi: 10.3390/vaccines13080781

Authors: Ying Xu Weihao Zhao Yuhan Zhu Bo Sun Congmei Wu Yuhe Yin

Objectives: Research on the immunocastration vaccine is of great significance for animal management. In this study, the gonadotropin-releasing hormone (GnRH) ferritin nanoparticle vaccine was constructed using Spy Catcher-Spy Tag (SC-ST) as a delivery system; Methods: The Spy Catcher was constructed to fuse with the expression vector pET-30a-SF of ferritin nanoparticles. Two polypeptides, STG1: Spy Tag-GnRH I-PADRE and STG2: Spy Tag-GnRH I-GnRH II, coupled to SF in vitro to form two nanoparticles, were designed and synthesized to detect castration effects in mice. We mixed them with the adjuvant MONTANIDE ISA 206 VG to explore the adjuvant’s effect on immunogenicity; Results: All immunized groups produced anti-GnRH specific antibodies after the second immunization, which was significantly higher in the immunized group and the combined adjuvant group than in the control group, and the immune response could still be detected at the 12th week. The concentrations of testosterone, follicle-stimulating hormone, and luteinizing hormone in serum were significantly decreased. The number of sperm in the epididymis of mice in each immune group was significantly reduced, and the rate of sperm deformity was high; Conclusions: The two ferritin-based GnRH nanoparticles developed in this study can significantly cause testicular atrophy, decreased gonadal hormone concentration, decreased sperm count, and increased deformity rate in male mice. These findings provide experimental evidence supporting their potential application in animal immunocastration.

Vaccines doi: 10.3390/vaccines13080780

Authors: Cheng Cheng Jeffrey C. Boyington Edward K. Sarfo Cuiping Liu Danealle K. Parchment Andrea Biju Angela R. Corrigan Lingshu Wang Wei Shi Yi Zhang Yaroslav Tsybovsky Tyler Stephens Adam S. Olia Audrey S. Carson Syed M. Moin Eun Sung Yang Baoshan Zhang Wing-Pui Kong Peter D. Kwong John R. Mascola Theodore C. Pierson

Background: Vaccines that stimulate systemic and mucosal immunity to a level required to prevent SARS-CoV-2 infection and transmission are an unmet need. Highly protective hepatitis B and human papillomavirus nanoparticle vaccines highlight the potential of multivalent nanoparticle vaccine platforms to provide enhanced immunity. Here, we report the construction and characterization of self-assembling 60-subunit icosahedral nanoparticle SARS-CoV-2 vaccines using the bacterial enzyme lumazine synthase (LuS). Methods and Results: Nanoparticles displaying prefusion-stabilized SARS-CoV-2 spike ectodomains fused to the surface-exposed amino terminus of LuS were designed using structure-guided approaches. Negative stain-electron microscopy studies of purified nanoparticles were consistent with self assembly into 60-mer nanoparticles displaying 20 spike trimers. After two intramuscular doses, these purified spike-LuS nanoparticles elicited significantly higher SARS-CoV-2 neutralizing activity than spike trimers in vaccinated mice. Furthermore, intramuscular DNA priming and intranasal boosting with a SARS-CoV-2 LuS nanoparticle vaccine stimulated mucosal IgA responses. Conclusion: These data identify LuS nanoparticles as highly immunogenic SARS-CoV-2 vaccine candidates and support the further development of this platform against SARS-CoV-2 and its emerging variants.

Vaccines doi: 10.3390/vaccines13080779

Authors: Kazuya Hiiragi Soichiro Obata Masafumi Yamamoto Mai Shimura Chika Akamatsu Azusa Tochio Mayumi Hagiwara Aya Mochimaru Ai Kiyose Miki Tanoshima Etsuko Miyagi Shigeru Aoki

Background/Objective: Maternal immunization is highly recommended, particularly in developed countries. However, its awareness among pregnant women in Japan remains low. This study aimed to assess the awareness and attitudes toward maternal immunization among pregnant women in Japan and to identify the factors that may promote its acceptance. Methods: We conducted a cross-sectional questionnaire survey among pregnant women attending antenatal checkups at nine facilities in Kanagawa Prefecture, Japan, from August 2024 to January 2025. The survey assessed knowledge and intention regarding maternal immunization for influenza, pertussis, respiratory syncytial virus (RSV), and group B streptococcus (GBS) as well as attitudes toward vaccination costs and information sources. Results: Overall, 523 respondents were included in this study. The overall awareness of maternal immunization was 16%. Willingness to receive vaccinations during pregnancy was reported for influenza (68%), pertussis (58%), RSV (59%), and GBS (71%). A common reason for vaccine hesitancy included uncertainty about its effects on the fetus. The key factors associated with vaccine acceptance were higher educational attainment and prior knowledge of maternal immunization. Regarding costs, most respondents were willing to pay up to JPY 5000 (approximately USD 35). The most frequently prioritized sources were explanations from physicians, followed by explanations from midwives. Conclusions: Despite low awareness, vaccination intention was comparable to that reported in other countries. Points that may contribute to improved vaccine uptake were also identified. These findings may lead to the prevention of infectious diseases in newborns and infants in Japan and possibly improve public health.

Vaccines doi: 10.3390/vaccines13080778

Authors: Johnathan D. Guest Yi Zhang Daniel Flores Emily Atkins Kuishu Ren Yingyun Cai Kim Rosenthal Zimeng Wang Kihwan Kim Charles Chen Richard Roque Bei Cheng Marianna Yanez Arteta Liping Zhou Jason Laliberte Joseph R. Francica

Background/Objectives: SARS-CoV-2 vaccine candidates comprising the receptor binding domain (RBD) of the spike protein have been shown to confer protection against infection. Previous research evaluating vaccine candidates with SARS-CoV-2 RBD fused to ferritin (RBD-ferritin) and other scaffolds suggested that multimeric assemblies of RBD can enhance antigen presentation to improve the potency and breadth of immune responses. Though RBDs directly fused to a self-assembling scaffold can be delivered as messenger RNA (mRNA) formulated with lipid nanoparticles (LNPs), reports of SARS-CoV-2 vaccine candidates that combine these approaches remain scarce. Methods: Here, we designed RBD fused to AP205 or TIP60 self-assembling nanoparticles following a search of available structures focused on several scaffold properties. RBD-AP205 and RBD-TIP60 were tested for antigenicity following transfection and for immunogenicity and neutralization potency when delivered as mRNA in mice, with RBD-ferritin as a direct comparator. Results: All scaffolded RBD constructs were readily secreted to transfection supernatant and showed antigenicity in ELISA, though clear heterogeneity in assembly was observed. RBD-AP205 and RBD-TIP60 also exhibited robust antibody binding and neutralization titers in mice that were comparable to those elicited by RBD-ferritin or a full-length membrane-bound spike. Conclusions: These data suggest that AP205 and TIP60 can present RBD as effectively as ferritin and induce similar immune responses. By describing additional scaffolds for multimeric display that accommodate mRNA delivery platforms, this work can provide new tools for future vaccine design efforts.

Vaccines doi: 10.3390/vaccines13080777

Authors: Miriam Viktov Thygesen Charlotte Strandhave Jeanette M?lgaard Kiib Randi Berg Malene S?th Andersen Emma Berggren Dall Bodil Gade Hornstrup Hans Christian ?stergaard Frank Holden Mose Jon Waarst Gregersen S?ren Jensen-Fangel Jesper N?rgaard Bech Henrik Birn Marianne Kragh Thomsen Rasmus Offersen

Background: Kidney transplant recipients (KTRs) exhibit a significantly diminished immune response to Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) vaccines compared with the general population, primarily due to ongoing immunosuppressive therapy. This study evaluated the immunogenicity of a third SARS-CoV-2 mRNA vaccine dose in KTRs and assessed the association between antibody response and protection against SARS-CoV-2 breakthrough infection. Additionally, the clinical and immunological correlates of post-vaccination SARS-CoV-2 infection were examined. Methods: A prospective cohort of 135 KTRs received a third vaccine dose approximately six months following the second dose. Plasma samples were collected at baseline (pre-vaccination), six months after the second dose, and six weeks following the third dose. Humoral responses were assessed using SARS-CoV-2-specific Immunoglobulin G (IgG) titers and virus neutralization assays against wild-type (WT) and viral strains, including multiple Omicron sub-lineages. Results: After the third vaccine dose, 74% of the KTRs had detectable SARS-CoV-2-specific IgG antibodies, compared with 48% following the second dose. The mean IgG titers increased approximately ten-fold post-booster. Despite this increase, neutralizing activity against the Omicron variants remained significantly lower than that against the WT strain. KTRs who subsequently experienced a SARS-CoV-2 breakthrough infection demonstrated reduced neutralizing antibody activity across all variants tested. Additionally, individuals receiving triple immunosuppressive therapy had a significantly higher risk of SARS-CoV-2 breakthrough infection compared with those on dual or monotherapy. A multivariate machine learning analysis identified age and neutralizing activity against WT, Delta, and Omicron BA.2 as the most robust correlates of SARS-CoV-2 breakthrough infection. Conclusions: A third SARS-CoV-2 mRNA vaccine dose significantly improves SARS-CoV-2-specific IgG levels in KTRs; however, the neutralizing response against Omicron variants remains suboptimal. Diminished neutralizing capacity and intensified immunosuppression are key determinants of SARS-CoV-2 breakthrough infection in this immunocompromised population.

Vaccines doi: 10.3390/vaccines13080776

Authors: Jonathan F. Lovell Kazutoyo Miura Yeong Ok Baik Chankyu Lee YoungJin Choi Jeong-Yoon Lee Carole A. Long Michelle Ylade Roxas Lee-Llacer Norman De Asis Mitzi Trinidad-Aseron Jose Manuel Ranola Loreta Zoleta De Jesus Howard Her

Background: We previously reported an interim safety and immunogenicity analysis of a Phase 3 trial in the Philippines of the EuCorVac-19 (ECV-19) COVID-19 vaccine with the COVISHIELDTM (CS) comparator (ClinicalTrials.gov identifier NCT05572879). Here, we present full-year humoral immunogenicity analysis. Methods: Healthy adults over 18 years of age received two injections of ECV-19 or CS vaccines, with 4 weeks between prime and boost. Analysis was carried out in individuals with immunogenicity measurements available at all 4 timepoints (weeks 0, 6, 30, and 56; n = 535 for ECV-19 and n = 260 for CS). Results: 2 weeks after boosting (week 6), ECV-19 elicited higher median anti-RBD IgG (1512 vs. 340 BAU/mL, p < 0.001) and neutralizing antibodies (1280 vs. 453 median microneutralization (MN) titer, p < 0.001) compared to CS. Anti-RBD IgG remained higher for ECV-19 compared to CS through week 30 (412 vs. 238 BAU/mL, p < 0.001) and 56 (425 vs. 260 BAU/mL, p < 0.001). MN titers remained higher for ECV-19 compared to CS through week 30 (640 vs. 453, p < 0.001) and 56 (453 vs. 320, p < 0.001). Correlation between anti-RBD IgG and neutralization titers persisted throughout the study. Women generally exhibited greater antibody responses than men. In the first six months following immunization, the ECV-19 group had a median antibody half-life of 80 days for anti-RBD IgG and 112 days for MN titer. In the subsequent six months, antibody half-life increased to 237 days for anti-RBD IgG and 168 days for MN titer. Conclusions: Following initial prime-boost vaccination, ECV-19 maintained higher anti-RBD IgG and neutralizing antibody titers relative to the CS comparator over a full-year period.

Vaccines doi: 10.3390/vaccines13070775

Authors: Qingjun Chen Li Cai Xinjun Lv Si Liu Cheng Liu Jiayang Liu Xiaoqiang Liu Wenwu Yin Chuanlin Wang Zhenggang Zhu

Background: Since the introduction of Pasteur’s rabies vaccine in 1885, rabies prophylaxis and post-exposure prophylaxis (PEP) have been widely administered globally under the recommendation of the World Health Organization (WHO). However, 124 documented cases of PEP failure had been reported worldwide between 1980 and 2023. Additionally, sporadic media reports from China showed occasional PEP failures between 2017 and 2024. Rabies remains a serious public health problem in over 150 countries and regions. Methods: In this review, we summarize PEP procedures recommended by the Advisory Committee on Immunization Practices (ACIP) and the WHO. We also analyze potential contributing factors to PEP failure, propose a concept of circulating antibodies, and discuss their roles in PEP. Furthermore, we summarize key guidelines for clinical trial design from the U.S. Food and Drug Administration (FDA) and China’s Center for Drug Evaluation (CDE), as well as the latest developments in monoclonal antibody (cocktail) therapies. Results: Adherence to core PEP practices, such as wound cleansing, infiltration of wounds with immunoglobulin (mAbs), and administration of vaccines, and broader societal involvement are crucial for preventing rabies infection in most cases. For high-risk exposures or immunocompromised individuals, the provision of circulating antibodies through high-dose human rabies immune globulin (HRIG) or mAbs is of utmost importance for preventing PEP failure. Conclusions: Early, high-concentration circulating antibodies are important for preventing PEP failure. Addressing the global issue of rabies requires involvement of the entire society. Only through collective efforts can we tackle this neglected disease and achieve WHO’s goal of “zero by 30”.

Vaccines doi: 10.3390/vaccines13070774

Authors: Mónica Espinar-García Isabel María Vallejo-Bermúdez María ángeles Onieva-García Irene Reina-Alfonso Luis Llapa-Chino Pablo álvarez-Heredia Inmaculada Salcedo Rafael Solana Alejandra Pera Alexander Batista-Duharte

Background: Annual influenza vaccine updates target viral drift, but immune responses may be biased by original antigenic sin (OAS). Few studies have explored this across closely related strains. This study examines how OAS shapes responses to sequential influenza variants in the context of seasonal vaccination. Methods: We conducted a prospective, longitudinal study to assess the humoral immune response to the 2023–2024 seasonal influenza vaccine containing the A/Victoria/4897/2022 (H1N1) strain. Bioinformatic analyses compared the hemagglutinin (HA) sequences of A/Victoria/4897/2022 and the antigenically related A/Victoria/2570/2019 strain. B-cell epitopes were mapped with BepiPred-3.0 and BepiBlast, and their physicochemical properties analyzed via accessibility, β-turns, flexibility, and hydrophilicity. Antibody responses were measured pre- and 28 days post-Vaxigrip Tetra vaccination in young (18–35) and older (>65) adults, stratified by cytomegalovirus (CMV) serostatus. HA sequences showed >97% identity, with variations mainly in the globular head. Predicted B-cell epitopes overlapped variable sites, suggesting possible immune escape. Despite having been vaccinated against the 2022 strain, serology showed higher antibody titers against the 2019 HA strain in all participants. This pattern suggests a potential antigen imprinting effect, though confirmation awaits further analysis. Age groups differed: older adults showed greater variability, while younger CMV+ individuals tended toward stronger 2019 HA responses. Conclusions: These findings suggest a complex interplay of factors shaping immune responses, though the imprinting effect and the potential role of CMV warrant further exploration in larger, more focused studies.

Vaccines doi: 10.3390/vaccines13070773

Authors: Yodira Guadalupe Hernandez-Ruiz Erika Zoe Lopatynsky-Reyes Rolando Ulloa-Gutierrez María L. Avila-Agüero Alfonso J. Rodriguez-Morales Jessabelle E. Basa Frederic W. Nikiema Enrique Chacon-Cruz

The 100-Day Mission, coordinated by the Coalition for Epidemic Preparedness Innovations (CEPI) and endorsed by significant international stakeholders, aims to shorten the timeframe for developing and implementing vaccines to 100 days after the report of a new pathogen. This ambitious goal is outlined as an essential first step in improving pandemic preparedness worldwide. This review highlights the mission’s implementation potential and challenges by examining it through the lens of low- and middle-income countries (LMICs), which often face barriers to equitable vaccine access. This article explores the scientific, economic, political, and social aspects that could influence the mission’s success, relying on lessons learned from previous pandemics, such as the Spanish flu, H1N1, and COVID-19. We also examined important cornerstones like prototype vaccine libraries, accelerated clinical trial preparedness, early biomarkers identification, scalable manufacturing capabilities, and rapid pathogen characterization. The review also explores the World Health Organization (WHO) Pandemic Agreement and the significance of Phase 4 surveillance in ensuring vaccine safety. We additionally evaluate societal issues that disproportionately impact LMICs, like vaccine reluctance, health literacy gaps, and digital access limitations. Without intentional attempts to incorporate under-resourced regions into global preparedness frameworks, we argue that the 100-Day Mission carries the risk of exacerbating already-existing disparities. Ultimately, our analysis emphasizes that success will not only rely on a scientific innovation but also on sustained international collaboration, transparent governance, and equitable funding that prioritizes inclusion from the beginning.

Vaccines doi: 10.3390/vaccines13070772

Authors: Raul Ramos Pupo Laura M. Reyes Diaz Gisela M. Suarez Formigo Yusnaby Borrego Gonzalez Miriam Lastre Gonzalez Danay Saavedra Hernandez Tania Crombet Ramos Belinda Sanchez Ramirez Roberto Grau Niels Hellings Piet Stinissen Oliver Perez Jeroen F. J. Bogie

Background/Objectives: The ongoing evolution of SARS-CoV-2 has highlighted the limitations of parenteral vaccines in preventing viral transmission, largely due to their failure to elicit robust mucosal immunity. Methods: Here, we evaluated an intranasal (IN) vaccine formulation consisting of recombinant receptor-binding domain (RBD) adsorbed onto human probiotic Bacillus subtilis DG101 spores. Results: In BALB/c mice, IN spore-RBD immunization induced strong systemic and mucosal humoral responses, including elevated specific IgG, IgM, and IgA levels in serum, bronchoalveolar lavage fluid (BALF), nasal-associated lymphoid tissue (NALT), and saliva. It further promoted mucosal B cell and T cell memory, along with a Th1/Tc1-skewed T cell response, characterized by increased IFN-γ-expressing CD4+ and CD8+ T cells in the lungs. Conclusions: All in all, these findings highlight the potential of intranasal vaccines adjuvanted with probiotic B. subtilis spores in inducing sterilizing immunity and limiting SARS-CoV-2 transmission.

Vaccines doi: 10.3390/vaccines13070771

Authors: Lorenzo Ippoliti Andrea Pizzo Agostino Paolino Luca Coppeta Giuseppe Bizzarro Cristiana Ferrari Andrea Mazza Claudia Salvi Ersilia Buonomo Fabian Cenko Andrea Magrini Antonio Pietroiusti

Background: Despite the widespread implementation of childhood vaccination programmes, hepatitis B virus (HBV) infection remains an ongoing occupational risk for healthcare students. In multi-ethnic and international university settings, differences in vaccination programmes and immune responses must be considered. This retrospective study aimed to assess the prevalence of protective levels of anti-HBs among medical students at an international university in Rome, exploring associations with demographic and vaccination-related factors. Methods: Data were collected from routine occupational health surveillance conducted in 2023. Anti-HB titres were measured in 507 students, and information on age, sex, country of birth, age at vaccination, and time since the last dose was analysed. Results: Overall, 55.0% of students had antibody levels of at least 10 mIU/mL, indicating serological protection. Higher seroprotection rates were observed among students vaccinated in the first year of life compared to those vaccinated later. A significant decline in antibody titres was also associated with longer intervals since vaccination. Students born outside Europe tended to show lower levels of protection. Conclusions: These results emphasise the importance of screening future healthcare professionals and continuously monitoring antibody titres to help reduce HBV infections.

Vaccines doi: 10.3390/vaccines13070770

Authors: Maribel Gonzalez Tome Rosa Gonzalez-Quevedo Maria Escudeiro dos Santos Hans Juergen Dornbusch Sabine Straus Emer Cooke

Background: Neisseria meningitidis B is one of the main causative pathogens of meningitis and other forms of severe meningococcal disease. In the past decade, meningococcal B vaccines have been developed to address this infection and its sequelae. Objective: This article aims to present an example of how the EU regulatory framework allowed the early authorisation of two life-saving vaccines initially based on immunogenicity surrogates of clinical evidence. This was subsequently followed by post-marketing surveillance providing real-world evidence to support their safety profile and impact on the paediatric population in the EU. Methods: We review the evidence supporting the initial regulatory approval of the vaccines, the confirmatory data demonstrating vaccine effectiveness post-authorisation, and the real-world impact of these vaccines on the paediatric population. Results: Two vaccines were approved in the EU for active immunisation to prevent IMD caused by MenB (4CMenB in 2013 and MenB-fHBP in 2017). Both marketing authorisations were based on immunogenicity data (efficacy studies were not feasible due to the rarity of the disease) and safety data generated from pre-authorisation studies. Additional pharmacovigilance activities to further investigate the safety profile and effectiveness studies were requested to be conducted after approval. Both the effectiveness and safety profile of the vaccines were confirmed by these data. Conclusions: This paper illustrates that the EU medicines regulatory framework and safety monitoring system are robust. By supplementing the initial evidence with post-authorisation studies, further effectiveness and safety data enabled regulators to confirm the positive benefit–risk of the vaccines without delaying their access to the people who need them.

Vaccines doi: 10.3390/vaccines13070769

Authors: Jia-Zhen Cui Xiang-Hua Xiong Qing-Yang Wang Hao-Long Dong Gang Liu Hui-Peng Chen

Pathogenic flaviviruses are predominantly the pathogens of emerging and re-emerging infectious diseases, which have caused multiple public health emergencies globally and pose a serious threat to human health and social development. Although significant achievements have been made in vaccine research, issues such as limited protective effects and virulence reversion persist, making the development of novel vaccines against pathogenic flaviviruses a current research hotspot and challenge. ISFVs have recently attracted attention due to their high homology with pathogenic flaviviruses and unique inability to replicate in mammalian hosts. Multiple vaccine candidate strains constructed using ISFVs as scaffolds have demonstrated excellent safety and efficacy. This review summarizes the biological characteristics, host restriction factors, current applications in vaccine development, and challenges faced by ISFVs, providing a reference for future research on pathogenic flavivirus vaccines.

Vaccines doi: 10.3390/vaccines13070768

Authors: Kiruthiga Mone Shraddha Singh Fatema Abdullatif Meghna Sur Mahima T. Rasquinha Javier Seravalli Denise K. Zinniel Indranil Mukhopadhyay Raul G. Barletta Teklab Gebregiworgis Jay Reddy

Background/Objectives: Freund’s adjuvants induce different immunomodulatory effects, but their underlying molecular mechanisms are unclear. In this study, we investigated whether the immune-stimulating effects of the complete Freund’s adjuvant (CFA) involve the mechanisms of trained immunity (TI). Methods: We examined bone marrow cells (BMCs) isolated from CFA-immunized A/J mice to address this question. Incomplete Freund’s adjuvant (IFA) and Mycobacterium tuberculosis var. bovis Bacillus Calmette-Guérin (BCG) served as negative and positive controls, respectively. We evaluated cytokine profiles, metabolic, and epigenetic changes. Results: First, BMCs from all groups except saline showed varied levels of IL-1β, IL-6, and TNF-α. But expression of CCL5 and CXCL10 was significantly elevated only in the CFA and BCG groups. Transcriptionally, significant elevations were noted for TNF-α and IL-1β in the CFA and BCG groups, whereas CXCL10, IL-6, and IL-10 were upregulated in the CFA and BCG groups, respectively. Second, while BMCs from the BCG group expressed the markers of both the M1 and M2 macrophages, no clear trends were noted in the CFA and IFA groups. Third, cell lysates from the CFA group revealed metabolic reprogramming in the BMCs. Specifically, we observed an increased level of lactate, indicative of aerobic glycolysis, which is implicated in TI, and this was also detected in the IFA group. Fourth, epigenetic analysis revealed histone enrichment in the promoter region of TNF-α, in the CFA group, but to a lesser degree than the BCG group. However, no epigenetic changes were observed in the IFA group. Conclusions: Our data provide new insights into the mechanisms of Freund’s adjuvants and the immunomodulatory effects of CFA could involve the features of TI.

Vaccines doi: 10.3390/vaccines13070767

Authors: Ayesha Zahid Hazrat Ismail Jennifer C. Wilson I. Darren Grice

Outer-membrane vesicles (OMVs), naturally secreted by Gram-negative bacteria, have gained recognition as a versatile platform for the development of next-generation vaccines. OMVs are essential contributors to bacterial pathogenesis, horizontal gene transfer, cellular communication, the maintenance of bacterial fitness, and quorum sensing. Their intrinsic immunogenicity, adjuvant properties, and scalability establish OMVs as potent tools for combating infectious diseases and cancer. Recent advancements in genetic engineering and biotechnology have further expanded the utility of OMVs, enabling the incorporation of multiple epitopes and antigens from diverse pathogens. These developments address critical challenges such as antigenic variability and co-infections, offering broader immune coverage and cost-effective solutions. This review explores the unique structural and immunological properties of OMVs, emphasizing their capacity to elicit robust immune responses. It critically examines established and emerging engineering strategies, including the genetic engineering of surface-displayed antigens, surface conjugation, glycoengineering, nanoparticle-based OMV engineering, hybrid OMVs, and in situ OMV production, among others. Furthermore, recent advancements in preclinical research on OMV-based vaccines, including synthetic OMVs, OMV-based nanorobots, and nanodiscs, as well as emerging isolation and purification methods, are discussed. Lastly, future directions are proposed, highlighting the potential integration of synthetic biology techniques to accelerate research on OMV engineering.

Vaccines doi: 10.3390/vaccines13070766

Authors: Stephen Wiblin Yuen Lai Natalie Soulsby Jodie Hillen

Background: Older adults living in aged care are at risk of poor health outcomes due to influenza, pneumococcal disease, and herpes zoster infections. Despite these conditions being vaccine-preventable, little is known about vaccine uptake rates in the residential elderly care setting in Australia. Methods: This was a retrospective cohort study examining the medical records of residents of 31 aged care homes in Australia (n = 1108). Data were extracted from medical records for the period March 2023 to September 2023. The proportion of residents vaccinated against influenza, pneumococcal disease, and herpes zoster was calculated. Univariate and multivariate logistic regressions were used to identify possible demographic and other characteristics associated with the vaccination uptake. Results: This study included 1108 residents. Two-thirds (68%) were female, and the median age was 87 years. All residents had one or more comorbidities. Most (92.6%) had received an influenza vaccine within the prior two years, but only 38.3% had received a pneumococcal vaccine, and 16.8% had received herpes zoster vaccination. In all models, receipt of the other vaccines was a significant predictor for vaccine administration. The other factor associated with influenza vaccination was non-consumption of alcohol and younger age for herpes zoster vaccination. Conclusions: While there is a high uptake of influenza vaccines, there is a low uptake of both pneumococcal and herpes zoster vaccines in residents of aged care facilities. Further research into the barriers and enablers of vaccine uptake should be undertaken, with the goal of increasing the vaccination uptake in this vulnerable population.

Vaccines doi: 10.3390/vaccines13070765

Authors: Noémi Becza Lingling Yao Paul V. Lehmann Greg A. Kirchenbaum

Background: Measuring frequencies of antigen-specific memory B cells (Bmem), their immunoglobulin (Ig) class and subclass usage, cross-reactivity, and affinity can provide insights into the efficacy of future antibody responses in case of antigen re-encounter. B cell ImmunoSpot® assays can provide such information; however, like most cell-based tests, they require considerable amounts of blood to be drawn from the donor and this has hindered their inclusion in clinical trials and routine immune diagnostics. Methods: We introduce strategies for reducing the cell numbers required to 2–3 million peripheral blood mononuclear cells (PBMCs) per antigen, obtainable from 2–3 mL of blood from healthy adult donors. Results: Except when Bmem frequencies were very low, we found that testing PBMCs in singlet wells, but in serial dilution, enables as reliable Bmem frequency assessments as when testing replicate wells at a single fixed cell number. Additionally, B cell ImmunoSpot® assays can be multiplexed for detecting four Ig classes, or IgG subclasses, simultaneously and without loss of sensitivity. The requirement for low cell numbers and the retention of B cell functionality by cryopreserved PBMCs equivalent to freshly isolated material implies that fewer than the standard 10 million PBMCs per vial can be frozen. This would reduce the number of individuals who could not be tested for Bmem due to insufficient availability of PBMCs, a common problem with such assays. Conclusions: The predictable need for and recovery of cryopreserved PBMCs facilitates planning of and optimal cell utilization in B cell ImmunoSpot® assays and increases the practical feasibility of extensive Bmem characterization in larger cohorts.

Vaccines doi: 10.3390/vaccines13070764

Authors: Cong Liu Xingyun Wang Yueling Zheng Xingyue Gao Jiahui Jin Xing Cheng Yunjiao He Peng George Wang

Background: Acinetobacter baumannii (A. baumannii) has emerged as a critical human pathogen, causing high mortality rates among hospitalized patients and frequently triggering nosocomial outbreaks. The increasing prevalence of multidrug-resistant (MDR) A. baumannii poses a pressing threat to public health. To date, no commercially available vaccine against A. baumannii has been developed for clinical use. messenger RNA (mRNA)–lipid nanoparticle (LNP) vaccines have emerged as a promising vaccination strategy. Methods: In this work, we developed two mRNA vaccines targeting SmpA-PLD and the fusion protein of outer membrane proteins OmpK and Omp22. The mRNA was encapsulated in LNP and administered to BALB/c mice. We evaluated humoral and cellular immune responses, bacterial burden, inflammation, and protective efficacy against A. baumannii infection in a sepsis model. Results: These mRNA vaccines triggered robust humoral and cellular immune responses in BALB/c mice, reduced bacterial burden and inflammation in sepsis models, and provided significant protection against A. baumannii infection. Notably, the OmpK-Omp22 vaccine exhibited superior protective efficacy, reducing bacterial loads in various organs and improving survival rates in the sepsis model compared to the SmpA-PLD vaccine. Conclusions: Our findings demonstrate mRNA-LNP vaccine technology as a versatile and promising platform for the development of innovative therapeutics against A. baumannii, with the potential to mitigate acute disease and promote bacterial decolonization. These findings pave the way for the development of urgently needed and effective antibacterial vaccines.

Vaccines doi: 10.3390/vaccines13070763

Authors: Zhengqin Su Linlin Deng Dan Luo Jianying Ren Xiaozhen Shen Wenjie Liang Haibin Wei Xiong Zou Zhongyou Li Hai Li

Background: This study aims to evaluate the cost-effectiveness of providing the 23-valent pneumococcal polysaccharide vaccine (PPV23) free of charge versus self-paying vaccination among adults aged 60 years and older in Nanning, Guangxi, China. Methods: A decision tree–Markov model was developed to compare three strategies (government-funded free vaccination, self-funded vaccination, and no vaccination) over a 5-year time horizon. The model incorporated local epidemiological data and cost parameters, applying a 3% discount rate. Sensitivity analyses were conducted on key parameters, including vaccine effectiveness against pneumonia and pneumonia treatment costs. Results: The benefit–cost ratios for free and self-funded vaccination were 0.075 and 0.015, respectively, both below the cost-effectiveness threshold of 1. However, the free vaccination strategy resulted in a higher net benefit (USD 399,651.32) compared to the self-funded strategy (USD 222,594.14), along with a lower Incremental Cost-Effectiveness Ratio (ICER) (USD 1.47 per USD 0.14 of avoided disease cost). Although both strategies yielded benefit–cost ratios far below the conventional threshold of 1, the free strategy demonstrated relatively greater economic efficiency. Sensitivity analyses confirmed that vaccine effectiveness against pneumonia and treatment costs were key drivers of economic outcomes. Conclusions: While neither vaccination strategy achieved conventional cost-effectiveness benchmarks in this setting, the free PPV23 vaccination program demonstrated relatively greater economic efficiency compared to the self-funded approach; although neither strategy met the conventional cost-effectiveness thresholds, they should be considered for inclusion in regional health policy for older adults.

Vaccines doi: 10.3390/vaccines13070762

Authors: Buyani Ndlovu Albertha R. van Zyl Dirk Verwoerd Edward P. Rybicki Inga I. Hitzeroth

Background/Objectives: Beak and feather disease virus (BFDV) is the causative agent of psittacine beak and feather disease (PBFD), affecting psittacine birds. There is currently no commercial vaccine or treatment for this disease. This study developed a novel BFDV coat protein mRNA vaccine encapsidated by TMV coat protein to form pseudovirions (PsVs) and tested its immunogenicity alongside BFDV coat protein (CP) subunit and DNA vaccine candidates. Methods: mRNA and BFDV CP subunit vaccine candidates were produced in Nicotiana benthamiana and subsequently purified using PEG precipitation and gradient ultracentrifugation, respectively. The DNA vaccine candidate was produced in E. coli cells harbouring a plasmid with a BFDV1.1mer pseudogenome. Immunogenicity of the vaccine candidates was evaluated in African grey parrot chicks. Results: Successful purification of TMV PsVs harbouring the mRNA vaccine, and of the BFDV-CP subunit vaccine, was confirmed by SDS-PAGE and western blot analysis. TEM analyses confirmed formation of TMV PsVs, while RT-PCR and RT-qPCR cDNA amplification confirmed encapsidation of the mRNA vaccine candidate within TMV particles. Restriction digests verified presence of the BFDV1.1mer genome in the plasmid. Four groups of 5 ten-week-old African grey parrot (Psittacus erithacus) chicks were vaccinated and received two boost vaccinations 2 weeks apart. Blood samples were collected from all four groups on day 14, 28 and 42, and sera were analysed using indirect ELISA, which showed that all vaccine candidates successfully elicited specific anti-BFDV-CP immune responses. The subunit vaccine candidate showed the strongest immune response, indicated by higher binding titres (>6400), followed by the mRNA and DNA vaccine candidates. Conclusions: The candidate vaccines present an important milestone in the search for a protective vaccine against PBFD, and their inexpensive manufacture could considerably aid commercial vaccine development.

Vaccines doi: 10.3390/vaccines13070761

Authors: Sofia M. Gulova Uliana S. Veselkina Irina V. Astrakhantseva

The emergence of a novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus closely related to SARS-CoV and officially known as Betacoronavirus pandemicum precipitated a substantial surge in vaccine development that culminated during the global COVID-19 pandemic. At present, there are dozens of vaccines for the prevention of SARS-CoV-2 being utilized across the globe. However, only 10 of these vaccines have been authorized by the World Health Organization (WHO). These include mRNA-based, viral vector, subunit and whole-virion inactivated vaccines. At the current end of the pandemic, there has been a decline in the global vaccination rate, both for the general population and for those most at risk of severe illness from the virus. This suggests that the effectiveness of the vaccines may be waning. The decline occurs alongside a decrease in testing and sequencing for SARS-CoV-2. Furthermore, the process of tracking viruses becomes increasingly complex, thereby providing a selective advantage for SARS-CoV-2 and allowing it to evolve stealthily. In this review, we provide a comprehensive overview of viral evolution and vaccine development. We also discuss ways to overcome viral variability and test universal vaccines for all SARS-CoV-2 variants.

Vaccines doi: 10.3390/vaccines13070760

Authors: Dongxiao Liu Lorenza Bellusci Hana Golding Surender Khurana

Our study demonstrates that IVIG lots manufactured in 2023–2024 contain neutralizing antibodies against circulating Omicron variants, including KP.3 and XEC. These variants are resistant to all convalescent plasma and IVIG preparations produced prior to 2023. Therefore, recent IVIG lots may provide some protection against COVID-19 caused by circulating SARS-CoV-2 variants.

Vaccines doi: 10.3390/vaccines13070758

Authors: Shiyan Wang Wenjie Jiao Dannan Zhao Yuzhu Gong Jingying Ni Huawei Wu Jige Du Tuanjie Wang Chunsheng Yin

Background: Canine parvovirus (CPV) is a highly pathogenic virus that predominantly affects puppies, with mortality rates exceeding 70%. Although commercial multivalent live attenuated vaccines (MLV) are widely employed, their efficacy is often compromised by maternal antibody interference. Consequently, the development of novel vaccines remains imperative for effective CPV control. Methods: Recombinant CPV VP2 protein (rVP2) and canine interlukine 12 protein (rcIL-12) were expressed using the Bac-to-Bac baculovirus expression system and the biological activity of these proteins was assessed through hemagglutination, Cell Counting Kit-8 (CCK8) and IFN-γ induction assays. The combined immunoenhancement effect of rVP2 and rcIL-12 protein was evaluated in puppies. Results: Both rVP2 and rcIL-12 were successfully expressed and purified, exhibiting confirmed antigenicity, immunogenicity, and bioactivity. Co-administration of rVP2 with rcIL-12 elicited higher neutralizing antibody titer (6–7 times higher), complete challenge protection efficiency (no clinical symptoms and tissue and organ lesions), fewer viral shedding (decreasing significantly 8-day post challenge) and superior viral blockade (lower viral load in the organism) compared to rVP2 alone. Conclusions: Our findings demonstrate that rVP2 co-administered with rcIL-12 induces robust protective immunity in puppies and significantly mitigated the inhibitory effects of maternal antibodies. This represents a promising strategy for enabling earlier vaccination in puppies and rational design of CPV subunit vaccines.

Vaccines doi: 10.3390/vaccines13070759

Authors: Simon Woelfel Joel Dütschler Daniel Junker Marius K?nig Georg Leinenkugel Claudia Krieger Samuel Truniger Annett Franke Seraina Koller Katline Metzger-Peter Nicola Frei STAR SIGN Study Investigators STAR SIGN Study Investigators Werner C. Albrich Matthias Friedrich Jan Hendrik Niess Nicole Schneiderhan-Marra Alex Dulovic Wolfgang Korte Justus J. Bürgi Stephan Brand

Background: Mucosal immunity plays a pivotal role in preventing infections with SARS-CoV-2. While COVID-19 mRNA vaccines induce robust systemic immune responses in patients with inflammatory bowel disease (IBD), little is known about their efficacy in the mucosal immune compartment. In this sub-investigation of the ongoing STAR-SIGN study, we present the first analysis of mucosal immunity elicited by XBB.1.5 mRNA vaccines in immunocompromised patients with IBD. Methods: IgG and IgA antibodies targeting the receptor-binding domain of the SARS-CoV-2 JN.1 variant were quantified longitudinally in the saliva of IBD patients using the multiplex immunoassay MultiCoV-Ab. Antibody levels were quantified before and 2–4 weeks after vaccination with XBB.1.5 mRNA vaccines. All patients previously received three doses with original COVID-19 vaccines. Results: Mucosal IgG antibodies were readily induced by XBB.1.5 mRNA vaccines (p = 0.0013 comparing pre- and post-vaccination levels). However, mucosal IgA levels were comparable before and after vaccination (p = 0.8233). Consequently, mucosal IgG and IgA antibody levels correlated only moderately before and after immunization (pre-vaccination: r = 0.5294; p = 0.0239; post-vaccination: r = 0.4863; p = 0.0407). Contrary to a previous report in healthy individuals, vaccination did not induce serum IgA in patients with IBD (p = 0.5841 comparing pre- and post-vaccination levels). These data suggest that COVID-19 mRNA vaccines fail to elicit mucosal IgA in patients with IBD. Conclusions: Since mucosal IgA plays a pivotal role in infection control, the lack of IgA induction indicates that patients lack sufficient protection against SARS-CoV-2 infections which warrants the development of mucosal COVID-19 vaccines.

Vaccines doi: 10.3390/vaccines13070757

Authors: Sven G?bel Tilia Zinnecker Ingo Jordan Volker Sandig Andrea Vervoort Jondavid de Jong Jean-Simon Diallo Peter Satzer Manfred Satzer Kai Dallmeier Udo Reichl Yvonne Genzel

Background: Modern viral vector production needs to consider process intensification for higher yields from smaller production volumes. However, innate antiviral immunity triggered in the producer cell may limit virus replication. While commonly used cell lines (e.g., Vero or E1A-immortalised cells) are already compromised in antiviral pathways, the redundancy of innate signaling complicates host cell optimization by genetic engineering. Small molecules that are hypothesized to target antiviral pathways (Viral Sensitizers, VSEs) added to the culture media offer a versatile alternative to genetic modifications to increase permissiveness and, thus, viral yields across multiple cell lines. Methods: To explore how the yield for a chimeric Zika vaccine candidate (YF-ZIK) could be further be increased in an intensified bioprocess, we used spin tubes or an Ambr15 high-throughput microbioreactor system as scale-down models to optimize the dosing for eight VSEs in three host cell lines (AGE1.CR.pIX, BHK-21, and HEK293-F) based on their tolerability. Results: Addition of VSEs to an already optimized infection process significantly increased infectious titers by up to sevenfold for all three cell lines tested. The development of multi-component VSE formulations using a design of experiments approach allowed further synergistic titer increases in AGE1.CR.pIX cells. Scale-up to 1 L stirred-tank bioreactors and 3D-printed mimics of 200 or 2000 L reactors resulted in up to threefold and eightfold increases, respectively. Conclusions: Addition of single VSEs or combinations thereof allowed a further increase in YF-ZIK titers beyond the yield of an already optimized, highly intensified process. The described approach validates the use of VSEs and can be instructive for optimizing other virus production processes.

Vaccines doi: 10.3390/vaccines13070756

Authors: Ashley H. Chinchilla Tyler C. Melton Salisa C. Westrick Tessa J. Hastings Leticia Vieira Grace T. Marley Delesha M. Carpenter

Background: Pneumococcal vaccination rates in the United States (US) remain suboptimal, especially for adults aged 19 to 64 with high-risk medical conditions. Community-pharmacy-based immunization services increase vaccine access, particularly in rural areas. This study describes the provision of pneumococcal immunization services, assesses the processes used to identify and confirm patient eligibility, and determines barriers to immunization services in rural community pharmacies. Methods: A cross-sectional survey was emailed to members of the Rural Research Alliance of Community Pharmacies, located in the southeastern US. The survey assessed which pneumococcal vaccines were offered, age groups, prescription requirements, and how patient eligibility was determined. In addition, participants were asked to rate a series of patient-related and organizational barriers to pneumococcal vaccination. Results: Ninety-four pharmacies completed the survey, with most (96.8%) offering pneumococcal vaccines, most commonly PCV20 (95.6%). Most pharmacies vaccinated patients upon request (98.9%) or when patients presented with a prescription (82.4%), but few proactively contacted patients to schedule the vaccination (17.6%). Pharmacists most often administered pneumococcal vaccines to patients aged 65 and older and used patient age and immunization information systems to identify eligible patients. The most common patient-related barrier was the patient’s belief that they do not need the vaccine. The most common organizational barriers were inadequate reimbursements for vaccine administration and vaccine products. Conclusions: Pneumococcal vaccinations are commonly offered in rural community pharmacies, which play an important role in immunization access. With recent guideline changes to the age-based recommendation, there is an opportunity to optimize strategies to increase vaccine uptake.

Vaccines doi: 10.3390/vaccines13070755

Authors: Laura C. Zwiers Diederick E. Grobbee Rob Schneijdenberg Corine Baljé Samantha St. Laurent Daina B. Esposito Lei Zhu Veronica V. Urdaneta Magalie Emilebacker Daniel Weibel Felipe Villalobos Carlo Alberto Bissacco Arantxa Urchueguía Fornes Juan José Carreras-Martínez Anteneh A. Desalegn Angela Lupattelli Lei Wang Jannik Wheler Vera Ehrenstein Denise Morris Catherine Fry Marjolein Jansen Brianna M. Goodale David S. Y. Ong

Background: Myocarditis and pericarditis are recognised risks following COVID-19 vaccination, including the mRNA-1273 vaccine. Most cases occur shortly following the second dose of this vaccine, and incidence is highest among young males. However, little is known about risk factors beyond age and sex and about the longer-term clinical course. This study aims to identify possible risk factors for myocarditis and pericarditis following mRNA-1273 vaccination, to characterise the clinical course of myocarditis and pericarditis, both associated with mRNA-1273 vaccination and not associated with vaccination, and to identify risk factors for severe outcomes (i.e., cardiac or thromboembolic complications, severe hospital outcomes, all-cause hospital readmission, and death). Methods: This study is being conducted within the Vaccine Monitoring Collaboration for Europe (VAC4EU) association using routinely collected healthcare data from five data sources from four European countries (Denmark, Norway, Spain, and the United Kingdom). The study is being performed using a common data model, and all analyses are performed separately in each data source in a federated manner following a common protocol. A case–cohort analysis set is identified within each data source for identifying potential risk factors for myocarditis and pericarditis following mRNA-1273 vaccination using logistic regression analysis. The clinical course of myocarditis and pericarditis is being assessed using a cohort study design and describes all cases (i.e., cases associated with mRNA-1273 and unexposed cases). Cox regression analysis is applied to assess the associations between risk factors and several follow-up outcomes. Conclusions: This protocol describes the study methodology of an international collaborative initiative with the aim of assessing the risk factors and clinical course of myocarditis and pericarditis following mRNA-1273 vaccination using a federated network of five European data sources.

Vaccines doi: 10.3390/vaccines13070754

Authors: Mohammad Enamul Hoque Kayesh Michinori Kohara Kyoko Tsukiyama-Kohara

Powassan virus is an emerging tick-borne flavivirus that poses a significant threat to human health. The outcome of Powassan virus infection is shaped by both viral factors and the host immune response. While this review aimed to examine the innate immune response, particularly toll-like receptor-mediated immune responses to Powassan virus, data specific to the immune response to Powassan virus remain scarce. Therefore, we focused on toll-like receptor responses to related flaviviruses to infer possible mechanisms of host response. Insights from both in vivo and in vitro studies are critical for guiding the development of effective therapeutic and preventive strategies. Currently, there are no clinically approved treatments or vaccines for Powassan virus, highlighting the urgent need for their development. We also highlight recent progress in POWV vaccine development, with an emphasis on the potential use of toll-like receptor agonists as adjuvants to enhance immunogenicity and improve vaccine efficacy.

Vaccines doi: 10.3390/vaccines13070753

Authors: Muntasir Alam Md Jowel Rana Asma Salauddin Emma Bentley Gathoni Kamuyu Dipok Kumer Shill Shafina Jahan Mohammad Mamun Alam Md Abu Raihan Mohammed Ziaur Rahman Rubhana Raqib Ali Azizi Mustafizur Rahman

Background: An effective vaccine against Nipah virus (NiV) is crucial due to its high fatality rate and recurrent outbreaks in South and Southeast Asia. Vaccine development is challenged by the lack of validated accessible neutralization assays, as virus culture requires BSL-4 facilities, restricting implementation in resource-limited settings. To address this, we standardized and validated a pseudotyped virus neutralization assay (PNA) for assessing NiV-neutralizing antibodies in BSL-2 laboratories. Methods: The NiV-PNA was validated following international regulatory standards, using a replication-defective recombinant Vesicular stomatitis virus (rVSV) backbone dependent pseudotyped virus. Assessments included sensitivity, specificity, dilutional linearity, relative accuracy, precision, and robustness. The assay was calibrated using the WHO International Standard for anti-NiV antibodies and characterized reference sera to ensure reliable performance. Findings: Preliminary evaluation of the developed NiV-PNA showed 100% sensitivity and specificity across 10 serum samples (5 positive, 5 negative), with a positive correlation to a calibrated reference assay (R2 = 0.8461). Dilutional linearity (R2 = 0.9940) and accuracy (98.18%) were confirmed across the analytical titer range of 11-1728 IU/mL. The assay also exhibited high precision, with intra-assay and intermediate precision geometric coefficients of variation of 6.66% and 15.63%, respectively. Robustness testing demonstrated minimal variation across different pseudotyped virus lots, incubation times, and cell counts. Conclusions: The validated NiV-PNA is a reproducible and scalable assay platform for quantifying NiV neutralizing antibodies, offering a safer alternative to virus culture. Its validation and integration into the CEPI Centralized Laboratory Network will enhance global capacity for vaccine evaluation and outbreak preparedness.

Vaccines doi: 10.3390/vaccines13070752

Authors: Jie Deng Chenyuan Qin Min Liu Jue Liu

Background: Influenza is a significant global respiratory infection, and vaccinating reproductive-age women, particularly in densely populated countries like China, cannot be overlooked. In this study, we aimed to determine influenza vaccination coverage, vaccine hesitancy, as well as associated factors among Chinese women aged 18–49 years old. Methods: A cross-sectional survey among women aged 18–49 years was conducted in China from 15 to 30 March 2023. We collected information such as past-year influenza vaccination, demographic characteristics, health-related factors, COVID-19-related factors, and perceived susceptibility and severity of influenza. Influenza vaccine acceptance among participants who did not receive influenza vaccination in the past year was also investigated. Multivariable logistic regression analyses were employed to investigate the influencing factors of vaccine coverage and vaccine hesitancy. Results: A total of 1742 reproductive-aged women were included in the final analysis. The past-year influenza vaccine coverage among women aged 18–49 years old was only 39.32% in China. Age ≥ 35 years (aOR = 0.72, 95% CI: 0.56–0.94), renting accommodation (aOR = 0.57, 95% CI: 0.44–0.75), and history of COVID-19 infection (aOR = 0.65, 95% CI: 0.47–0.89) and COVID-19 vaccine hesitancy (aOR = 0.39, 95% CI: 0.29–0.54) were all identified as negative correlates of influenza vaccine coverage among Chinese reproductive-aged women, while participants with a history of chronic diseases (aOR = 1.57, 95% CI: 1.23–2.01) and noticeable pandemic fatigue due to COVID-19 (aOR = 1.45, 95% CI: 1.05–2.00) were prone to have higher vaccination rates. Among reproductive-aged women who did not receive influenza vaccination in the past year, the hesitancy rate regarding future influenza vaccination was 31.79%. Factors such as older age, urban residence, living with others, poor self-rated health status, absence of chronic diseases, completion of full COVID-19 vaccination, COVID-19 vaccine hesitancy, pandemic fatigue, and failure to perceive the susceptibility and severity of influenza might increase influenza vaccine hesitancy. Discussion: Overall, a lower coverage rate of influenza vaccine was notably observed among Chinese reproductive-age women, as well as the hesitancy regarding future vaccination. To effectively mitigate the impact of influenza and reduce the incidence of associated diseases, it is imperative to devise targeted intervention strategies and policies tailored to reproductive-age women.

Vaccines doi: 10.3390/vaccines13070751

Authors: Yoshifumi Uwamino Takashi Yokoyama Yasunori Sato Shiho Tanaka Yuka Kamoshita Ayako Shibata Toshinobu Kurafuji Akiko Tanabe Tomoko Arai Akemi Ohno Ho Namkoong Tomoyasu Nishimura Masatoshi Wakui Mitsuru Murata Naoki Hasegawa Hiromichi Matsushita

Background: The long-term immune implications of administering more than four doses of COVID-19 vaccine and the impact of breakthrough infections are not fully understood. Research Design and Methods: We conducted a follow-up cohort study on Japanese healthcare workers who received more than three doses of the BNT162b2 vaccine. We assessed both the anti-SARS-CoV-2 antibody titer and cellular immunity in 429 participants and investigated the numbers, types, and brands of COVID-19 vaccines administered, as well as the episodes of COVID-19 infections after the third dose. Results: Individuals who received three total doses of vaccines with BTI episodes demonstrated higher antibody titers than those who received four total doses of vaccines with no BTIs. The cellular immune responses between these two groups were comparable. Conclusions: These findings suggest that BTIs occurring after the primary series of COVID-19 vaccinations (first to third dose) induced humoral immunity to the spike protein that is greater than that induced by booster doses (fourth or fifth dose) and elicit cellular immunity to the spike protein comparable to that of booster doses.

Vaccines doi: 10.3390/vaccines13070750

Authors: Akemi Hara Shun Watanabe Toyoaki Sawano Yuki Sonoda Hiroaki Saito Akihiko Ozaki Masatoshi Wakui Tianchen Zhao Chika Yamamoto Yurie Kobashi Toshiki Abe Takeshi Kawamura Akira Sugiyama Aya Nakayama Yudai Kaneko Hiroaki Shimmura Masaharu Tsubokura

Background: Hemodialysis patients, due to impaired kidney function and compromised immune responses, face increased risks from SARS-CoV-2. Anti-nucleocapsid IgG (anti-IgG N) antibodies are a commonly used marker to assess prior infection in the general population; however, their efficacy for hemodialysis patients remains unclear. Methods: A retrospective study of 361 hemodialysis patients evaluated anti-IgG N antibodies for detecting prior SARS-CoV-2 infection. Antibody levels were measured using a chemiluminescence immunoassay (CLIA) over the four time points. Boxplots illustrated antibody distribution across sampling stages and infection status. Logistic regression and receiver operating characteristic (ROC) curve analysis determined diagnostic accuracy, sensitivity, specificity, and optimal cutoff values. Results: Among the 361 hemodialysis patients, 36 (10.0%) had SARS-CoV-2 infection. Sex distribution showed a trend toward significance (p = 0.05). Boxplot analysis showed that anti-IgG N levels remained low in non-infected patients but increased in infected patients, peaking at the third sampling. Anti-IgG N demonstrated high diagnostic accuracy (AUC: 0.973–0.865) but declined over time (p = 0.00525). The optimal cutoff at C1 was 0.01 AU/mL (sensitivity 1.00, specificity 0.94). Adjusted models had lower predictive value. Conclusions: Anti-IgG N antibodies showed high diagnostic accuracy for detecting prior SARS-CoV-2 infection in hemodialysis patients, though performance declined over time. These findings highlight the need for tailored diagnostic strategies in this vulnerable population.

Vaccines doi: 10.3390/vaccines13070749

Authors: Sara Huerta-Yepez Jose D. Gonzalez Neha Sheik Senay Beraki Elango Kathirvel Ariel Rodriguez-Frandsen Po-Chun Chen Tiran Sargsyan Saleemulla Mahammad Mark R. Dybul Lu Chen Francois Binette Anahid Jewett

Background/Objectives: Pancreatic cancer remains the fourth leading cause of cancer-related deaths. While peripheral blood-derived mature dendritic cell (mDC) vaccines have shown potential in eliciting anti-tumor immune responses, clinical efficacy has been limited. This study aimed to enhance the potency and scalability of DC-based immunotherapy by developing an allogeneic DC platform derived from CD34+ hematopoietic stem cells (HSCs), genetically engineered to overexpress CD93, CD40L, and CXCL13, followed by maturation and tumor antigen pulsing. Methods: Engineered DCs were generated from CD34+ HSCs and matured in vitro after lentiviral transduction of CD93, CD40L, and CXCL13. Tumor lysates were used for antigen pulsing. A scrambled-sequence control DC was used for comparison. In vitro assays were performed to assess T cell activation and tumor cell killing. In vivo efficacy was evaluated using orthotopic pancreatic tumors in BLT and PBMC-humanized NSG mice established with the MiaPaca-2 (MP2) cell line. Results: Engineered DCs significantly enhanced T cell activation and tumor-specific cytotoxicity in vitro compared to control DCs. Antigen pulsing further amplified immune activation. In vivo, treated humanized mice showed increased CD4+, CD8+, and NK cell frequencies in peripheral blood and within tumors, correlating with reduced tumor burden. Conclusions: Our data shows that the antigen-pulsed, engineered DCs have the potency to activate immune cells, which leads to a significant reduction in pancreatic tumors and therefore could potentially provide an effective therapeutic opportunity for the treatment of pancreatic cancer and other solid tumors.

Vaccines doi: 10.3390/vaccines13070747

Authors: Can Wang Liping Peng Xiaotong Huang Tim K. Tsang

Background: Starting in early 2022, SARS-CoV-2 Omicron has driven large outbreaks in China, a predominantly infection-naive population with high inactivated vaccine coverage. This unique context provided a substantially less-confounded opportunity to evaluate how vaccination, public health, and social measures influenced severity. Methods: We systematically reviewed 86 studies (224 severity estimates) published from 2022 to 2024, reporting symptom and clinical severity outcomes (fever, cough, and sore throat; symptomatic, severe/critical, and fatal illness) of Omicron infections in China. Using meta-regression, we evaluated the associations of study setting, age group, vaccination status, predominant subvariants, and Oxford COVID-19 Government Response Tracker (OxCGRT) indices, including the Government Response Index (GRI), Containment and Health Index (CHI), and the Stringency Index (SI), with infection outcomes, adjusting for key confounders. Results: We found the primary or booster series of inactivated vaccines conferred strong protection against severe/critical illness (pooled relative risk (RR) 0.17 [95% CI: 0.09–0.33]) but did not reduce symptom frequency (RR 0.99 [95% CI: 0.95–1.02]). Each 10-unit increase in GRI or CHI was associated with 7% (95% CI: 1–12%) and 6% (95% CI: 1–10%) lower odds of symptomatic infection and 3% (95% CI: 1–4%) lower odds of severe/critical illness. Later subvariants (BA.5, BF.7, and XBB) showed 24–38% higher odds of upper respiratory symptoms versus BA.1. Conclusions: The data collection context significantly impacted severity estimates, with higher estimates from emergency hospitals. Overall, inactivated vaccines provided strong protection against severe/critical outcomes while stringent public health measures were associated with lower severity. Our findings underscore the importance of consistent and standardized protocols to produce reliable estimates of SARS-CoV-2 severity in evolving epidemiological contexts.

Vaccines doi: 10.3390/vaccines13070748

Authors: Andrea Trujillo Liesbeth Van Wesenbeeck Lina Salazar Liliana López Lotke Tambuyzer Annemie Buelens Kim De Clerck Oliver Lenz Leen Vijgen Marnix Van Loock Guillermo Herrera-Taracena Iván Darío Vélez Freya Rasschaert

Background: The evaluation of antiviral or vaccination strategies for the prevention of dengue infections in a traveler population would require extensive and complex studies. This prospective study aimed to identify a cohort of dengue naïve participants living in Medellín, a dengue endemic area, as a proxy for travelers and to determine the incidence of primary dengue virus (DENV) infection (symptomatic and asymptomatic) in this cohort. In Colombia, epidemic dengue waves occur every 3–4 years, with infected Aedes mosquitoes present in ~80% of the territory, including Medellín. Methods: Participants > 16 years of age, living in Medellín, were screened for anti-DENV immunoglobulin G (IgG). DENV seronegative participants were enrolled in this study. A serological anti-DENV survey was performed, with semiannual sample collections for up to 2 years. Acute DENV infections were evaluated by monitoring fever and testing for DENV nonstructural protein 1 and/or RNA. Results: Of the 4885 screened participants, 3008 participants (62%) were DENV seronegative and enrolled. Among them, 2263 (75%) completed this study, and 2644 (88%) had at least one serosurvey visit after baseline. Of those, 52 (2%) had laboratory-confirmed DENV seroconversion, and 19 (<1%) had febrile illness, but none had laboratory-confirmed DENV infection. Conclusions: This study identified a cohort of predominantly students, seronegative at study start, living in Medellín and serving as a proxy for a prospective DENV infection traveler population. Laboratory-confirmed primary DENV infection was found in 2% of participants, with <1% reporting febrile illnesses, meeting the WHO criteria for probable clinical dengue cases.

Vaccines doi: 10.3390/vaccines13070746

Authors: Beatriz Almeida Sampaio Maysa Santos Barbosa Matheus Gon?alves de Oliveira Manoel Neres Santos Júnior Bruna Carolina de Brito Guimar?es Emilly Stefane Souza Andres ágatha Morgana Bertoti da Silva Camila Pacheco Gomes Rafaela de Souza Bittencourt Thiago Macêdo Lopes Correia Lucas Santana Coelho da Silva Jurandir Ferreira da Cruz Rohini Chopra-Dewasthaly Guilherme Barreto Campos Jorge Timenetsky Bruno Lopes Bastos Lucas Miranda Marques

Background/Objectives: Contagious agalactia (CA) is a disease typically caused by Mycoplasma agalactiae, affecting small ruminants worldwide and being endemic in certain countries. CA causes severe economic losses due to mastitis, agalactia, and arthritis. As an alternative to existing immunoprophylactic measures, this study aimed to develop a recombinant subunit vaccine against M. agalactiae and evaluate its specific immune response in goats. Methods: Goats were divided into three groups: group 1 received recombinant proteins (P40 and MAG_1560), group 2 received formalin-inactivated M. agalactiae, and group 3 received Tris-buffered saline (negative control). All solutions were emulsified in Freund’s adjuvant. Animals were monitored for 181 days. IgG antibody production was assessed by ELISA, and peripheral blood mononuclear cells (PBMCs) were analyzed by real-time PCR for the expression of IL-1β, IFN-γ, IL-12, and MHC class II genes. Results: M. agalactiae-specific antibody response was observed for six months in the sera of animals from group 1. Analysis of cytokine gene expression revealed increased IL-1β mRNA levels over time in both experimental groups. In group 1, IFN-γ mRNA levels increased with P40 stimulation and decreased with MAG_1560. IL-12 mRNA expression decreased over time in group 1 with P40 stimulation, whereas group 2 showed increased IL-12 expression for both proteins. MHC-II expression was stimulated in both groups. Conclusions: The recombinant proteins induced antibody production and cytokine expression, demonstrating immunogenic potential and supporting their promise as vaccine candidates capable of eliciting both humoral and cellular immune responses against M. agalactiae.

Vaccines doi: 10.3390/vaccines13070745

Authors: Hongzhe Lin Yuxuan Jiang Yan Li Yiwei Zhong Mingyue Chen Weiyu Jiang Rong Xiang Najing Cao Lei Sun Xuanyi Wang Lu Lu Qiao Wang Guangyue Han Duan Ma Bin Wang

Background: Influenza remains a persistent public health challenge due to antigenic drift and shift, necessitating vaccines capable of eliciting broad and durable immunity. Hemagglutinin (HA) antigen serves as the critical target for eliciting protective immune responses against influenza. DNA vaccines offer distinct advantages over conventional platforms, including accelerated development and induction of both humoral and cellular immune responses. Methods: To optimize HA antigen presentation, we designed and systematically compared the immunogenicity and protective efficacy of HA antigen display strategies—bacteriophage T4 fibritin (HA-Foldon) and ferritin-based virus-like particles (HA-Ferritin)—versus monomeric HA DNA vaccines against seasonal influenza viruses. Results: HA-Ferritin showed superior structural stability. All vaccines induced similar HA-specific antibody levels, but HA-Ferritin elicited higher neutralizing antibodies and stronger T cell responses. Upon challenge, HA-Ferritin and HA-Foldon protected mice from weight loss and reduced lung virus loads by 3.27 and 0.76 times, respectively. Monomeric HA provided limited protection, with only 40% survival and minimal viral or pathological reduction. Conclusions: The HA-Ferritin DNA vaccine demonstrated enhanced immunogenicity and protection, supporting structured antigen display as a promising strategy for influenza DNA vaccine development.

Vaccines doi: 10.3390/vaccines13070744

Authors: Natalya Andreeva Ekaterina Martynova Polina Elboeva Milana Mansurova Ilnur Salafutdinov Aleksandr Aimaletdinov Rafil Khairullin Diksha Sharma Manoj Baranwal Sara Chandy Dilbar Dalimova Alisher Abdullaev Mirakbar Yakubov Albert Rizvanov Svetlana Khaiboullina Yuriy Davidyuk Emmanuel Kabwe

(1) Background: Hemorrhagic fever with renal syndrome (HFRS) remains a prevalent zoonosis in Eurasia. Orthohantavirus puumalaense (PUUV), carried by bank voles (Myodes glareolus), is the principal zoonotic pathogen of HFRS in this region. Despite ongoing efforts to develop effective drugs and vaccines against PUUV, this challenge remains. (2) Aim: In this study, we aimed to express a large quantity of the PUUV recombinant N (rN) protein using E. coli. We also sought to develop a protocol for extracting the rN protein from pellets, solubilizing, and refolding it to restore its native form. This protocol is crucial for producing a large quantity of rN protein to develop vaccines and diagnostic tools for HFRS. (3) Methods; PUUV S segment open reading frame (ORF) coding for N protein was synthesized and cloned into the plasmid vector pET-28 (A+). The ORF was transformed, expressed and induced in BL21(DE3) pLysS E. coli strain. Subsequently, rN protein was purified using immobilized metal affinity and ion chromatography. Immune reactivity of rN protein was tested by employing in house and commercial VektoHanta-IgG kit ELISA methods (both in vitro and in vivo). (4) Results: The best conditions for scaling up the expression of the PUUV rN protein were an incubation temperature of 20 °C during a 20 h incubation period, followed by induction with 0.5 mM IPTG. The most significant protein yield was achieved when the pellets were incubated in denaturing buffer with 8M urea. The highest yield of refolded proteins was attained using non-denaturing buffer (50 mM Tris-HCl) supplemented with arginine. A final 50 μL of PUUV rN protein solution with a concentration of 7 mg/mL was recovered from 1 L of culture. The rN protein elicited an antibody response in vivo and reacted with serum taken from patients with HFRS by ELISA in vitro. (5) Conclusion: Therefore, the orthohantavirus N protein’s ability to elicit immune response in vivo suggests that it can be used to develop vaccines against PUUV after conducting in vitro and in vivo studies to ascertain neutralising antibodies.

Vaccines doi: 10.3390/vaccines13070743

Authors: Chen Chen Dandan Ling Kai Ji Liang Tang Xiaojing Zhang Xishan Lu Xuemei Leng Changyao Tan Hongchao Wu Wenqiang Pang Quanren He Jerry Zhang Peng Gao Xiaotao Wang Linhui Wang Bo Ying

Background: Many new mRNA-based vaccine candidates in liquid mRNA-LNP formulations are under development; however, their stability limitations necessitate frozen storage, posing a significant challenge for long-term storage and transportation. Methods: In this study, an mRNA-LNP rabies vaccine, ABO1005, was prepared, freeze-dried and stored at 2–8 °C for 12-month storage stability evaluation. The immunogenicity, vaccine potency (the NIH method), and protective efficacy of ABO1005 were assessed in mice or dogs and compared to a commercialized inactivated vaccine. Results: Research conducted in mice indicated that the lyophilized vaccine exhibited comparable immunogenicity to its liquid form counterpart. Furthermore, the vaccine candidate elicited a robust humoral response lasting at least 175 days, and the specific antibody titers were not affected by the pre-administration of hyperimmune serum. In comparison to the commercialized inactivated vaccine (HDCV or PVRV), ABO1005 elicited significantly higher levels of humoral and cellular immunity. Vaccine potency testing (NIH) revealed that the potency of ABO1005 at 15 μg/dose was 8.85 IU/dose, which is substantially higher than the standard required for the lot release of rabies vaccines for current human use. In a post-exposure prophylaxis (PEP) study in Beagle dogs, the lyophilized vaccine provided 100% protection for dogs following a two-dose regimen (D0-D7), whereas commercially approved inactivated vaccine offered 83% protection. After storage at 2–8 °C for 12 months, no notable changes were observed in the particle size, encapsulation efficiency, and integrity of mRNA or in the immunogenicity of the lyophilized vaccine. Conclusions: This study successfully developed a formulation and process of freeze-drying for a rabies mRNA vaccine, paving the way for future lyophilized mRNA vaccine development.

Vaccines doi: 10.3390/vaccines13070742

Authors: Xin Rong Lim Shiyu Liu Hwee Siew Howe Khai Pang Leong Elampirai Elangovan Chiung-Hui Huang Kok Ooi Kong Bernard Yu Hor Thong Shawn Vasoo Bernard Pui Lam Leung

Background/Objectives: Neutralizing autoantibodies against type I interferons, particularly interferon-alpha (IFN-α), have been implicated in severe COVID-19 outcomes. This study investigated the prevalence and functional significance of anti-IFN-α autoantibodies (AAbs) in hospitalized unvaccinated COVID-19 patients and their association with COVID-19 disease severity. Methods: We retrospectively analyzed serum samples from 122 hospitalized COVID-19 patients (asymptomatic/mild: n = 69, moderate: n = 35, severe/critical: n = 18) and 32 healthy uninfected controls. Anti-IFN-α AAbs were quantified using a commercial enzyme-linked immunosorbent assay (ELISA) kit, with functional neutralization assessed via competitive ELISA and STAT1 phosphorylation inhibition. Statistical comparisons were performed using one-way ANOVA for parametric data and the Kruskal–Wallis test for non-parametric variables. Results: Anti-IFN-α AAbs were detected in 24.6% of COVID-19 patients, with all clinical subgroups showing significantly higher titers compared to healthy controls (p < 0.05). Although no significant differences in anti-IFN-α AAb levels were found between mild, moderate, and severe cases, patients with severe or critical COVID-19 had markedly higher mean titers (10,511.3 ng/mL) compared to non-severe (mild + moderate) cases (375.2 ng/mL, p < 0.001). Strongly neutralizing anti-IFN-α AAbs, with high titers (>20,000 ng/mL) and the ability to inhibit STAT1 phosphorylation, were identified in three severe COVID-19 cases. Anti-IFN-α AAb levels correlated positively with CRP (r = 0.80, p < 0.0001), LDH (r = 0.80, p = 0.001), and neutrophil count (r = 0.52, p = 0.003), and negatively with lymphocyte count (r = −0.59, p = 0.0006). Conclusions: Elevated and functionally neutralizing anti-IFN-α AAbs were associated with severe COVID-19. These findings support their role as a risk factor for poor outcomes and emphasize the importance of early COVID-19 vaccination. Screening may help identify high-risk individuals, particularly those unvaccinated or with immune vulnerabilities.

Vaccines doi: 10.3390/vaccines13070741

Authors: Barbara Poniedzia?ek Wiktoria Majewska Katarzyna Kondratiuk Aleksander Masny Anna Poznańska Karol Szymański Katarzyna ?uniewska Emilia Czajkowska Bartosz Mańkowski Lidia B. Brydak Krzysztof Tomasiewicz Robert Flisiak Piotr Rzymski

Background/Objectives: Respiratory syncytial virus (RSV) is a leading cause of respiratory infections across all age groups, with the greatest burden observed in young children and older adults. The COVID-19 pandemic significantly disrupted RSV circulation, resulting in an immunity gap and altered transmission dynamics. This study aimed to assess the seroprevalence of anti-RSV IgG antibodies in the Polish population during the 2023/2024 epidemic season. To our knowledge, this is the first study to characterize RSV seroprevalence at the population level in Poland. Methods: A total of 700 serum samples from individuals across different age groups were analyzed using a commercial assay to detect anti-RSV IgG antibodies. Seroprevalence and antibody levels, expressed as the index of positivity (IP), were examined by age and sex. Results: The overall seroprevalence of anti-RSV IgG antibodies was 91.4%. Antibody positivity increased markedly from 35.5% in infants aged 0–1 years to over 90% in children aged 4–5 years, reaching nearly universal levels in older age groups, including 99.1% in adults aged ≥60 years. Median IP values also rose with age, peaking in individuals aged ≥60 years. No significant differences in seroprevalence were observed between sexes, though older men showed slightly higher median IP values, potentially reflecting greater cumulative RSV exposure. Conclusions: This study provides key insights into the post-pandemic landscape of RSV immunity in Poland. The high seroprevalence across most age groups underscores widespread prior exposure, while the lower rates in infants highlight a continued vulnerability. These findings support the development and implementation of targeted immunization strategies, particularly for infants and older adults.