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Human Vaccines & Immunotherapeutics

Informa UK Limited

Preprints posted in the last 30 days, ranked by how well they match Human Vaccines & Immunotherapeutics's content profile, based on 25 papers previously published here. The average preprint has a 0.03% match score for this journal, so anything above that is already an above-average fit.

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A surrogate marker of protection confirms the efficacy of an AddaS03-adjuvanted West Nile virus subunit vaccine

Inoue, A.; Saito, S.; Maeda, K.; Itakura, Y.; Kobayashi, S.; Sasaki, M.; Gonzalez, G.; Hall, W. W.; Maenaka, K.; Orba, Y.; Sawa, H.; Tabata, K.

2026-04-21 microbiology 10.64898/2026.04.20.719748 medRxiv
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West Nile virus (WNV) is the causative agent of fatal West Nile encephalitis. To date, no human vaccine against WNV has been approved. Adjuvants are important for developing effective and affordable vaccines that enhance the immunogenicity and decrease the required antigen doses. In this study, we assessed the efficacy of AddaS03, a synthetic adjuvant analogous to AS03, in a WNV subunit vaccine composed of soluble recombinant envelope protein (sEnv). Using a passive immunization mouse model, we defined the neutralizing antibody titer threshold required for protection against lethal WNV infections and applied this threshold as a surrogate marker to evaluate adjuvant efficacy. AddaS03-adjuvanted formulations elicited markedly higher neutralizing antibody titers compared to Alhydrogel adjuvant 2% (Alhydrogel), even at suboptimal antigen doses, and consistently exceeded the defined protective threshold titer. Moreover, in a sequential challenge mouse model, AddaS03-adjuvanted vaccines completely protected mice from symptomatic WNV infections, whereas Alhydrogel-adjuvanted vaccines failed to confer full protection. Collectively, these findings demonstrate that AddaS03 is a promising adjuvant for WNV subunit vaccine development and highlights the utility of a passive immunization model for defining protective antibody thresholds as a surrogate marker for vaccine evaluation.

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Understanding inequalities in COVID-19 vaccination between migrants and non-migrants in Germany: The role of psychological factors of vaccine behaviour

Bartig, S.; Siegert, M.; Hoevener, C.; Michalski, N.

2026-04-17 public and global health 10.64898/2026.04.15.26350844 medRxiv
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Background: Understanding the underlying mechanisms for differences in vaccine uptake between migrants and non-migrants is crucial in order to design targeted interventions encouraging vaccination and to ensure vaccine-related equity. Therefore, this study examined to what extent migration-related disparities in COVID-19 vaccination were associated with psychological factors, based on the established 5C model of vaccine behaviour (Confidence, Complacency, Constraints, Calculation, Collective Responsibility). Methods: Data were obtained from the German study "Corona Monitoring Nationwide - Wave 2" (RKI-SOEP-2 study), which was carried out between November 2021 and March 2022. The association between COVID-19 vaccination and migration status, while considering the psychological factors, was investigated using multivariable binary logistic regressions. A decomposition analysis (Karlson-Holm-Breen method) was conducted to examine the extent to which migration-related disparities in vaccine uptake were associated with the psychological factors of the 5C framework. Results: Migrants were less likely to be vaccinated against COVID-19 compared to non-migrants, especially participants from the Middle East and North Africa (MENA) region. Our decomposition showed that almost two-thirds of the disparities in COVID-19 vaccine uptake between migrants and non-migrants were associated with the psychological factors (first-generation: 61.2%, second-generation: 64.2%). Confidence in safety of the vaccine was the most relevant factor in the 5C framework. Furthermore, the results highlighted the importance of a differentiated analysis regarding country of origin: While the 5C model accounted for only 19.4% of the difference between participants from the MENA region and non-migrants, the proportion for participants from Eastern Europe was 73.5%, suggesting that the underlying mechanisms for the lower uptake in the MENA group need further investigation. Conclusions: Overall, migration-related disparities in COVID-19 vaccination were significantly associated with differences in psychological factors of vaccine behaviour. To increase vaccine acceptance within the heterogeneous group of migrants in general, tailored and proactive health communication interventions are needed.

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Greater intergroup bias in vaccination attitudes among physicians than the general public

Murakami, M.; Ohtake, F.

2026-04-25 infectious diseases 10.64898/2026.04.23.26351641 medRxiv
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While vaccination conflicts have become apparent, physicians' attitudes toward those with differing views remain unclear. Through an online survey of 492 physicians and 5,252 members of the general public in Japan in February 2026, we investigated attitudes toward four vaccines (influenza, measles, HPV, and COVID-19). Intergroup bias was assessed as ingroup minus outgroup attitudes using a feeling thermometer. Multilevel regression examined associations with agreement group and physician status. Intergroup bias was significantly positive in both agreement and disagreement groups across all vaccine types, and was higher in the agreement group. Physicians exhibited higher intergroup bias than the general public. These findings indicate that vaccination conflict is bidirectional: physicians, often viewed as targets of hostility from vaccine-hesitant individuals, themselves exhibit greater intergroup bias toward those with opposing views. Interventions to raise physicians' awareness of their own bias, alongside communication strategies for vaccine-hesitant individuals, are needed.

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Dengue serotype-1 virus like particles induce antibody responses following HeLa cell expression

Shrestha, S.; Maharjan, A.; Raut, R.; Manandhar, B.; Khadka, B.; Poudel, A.; Joshi, T. R.; Chaurasia, D.; R.C, S.; Joshi, J.; Malla, R.; Karki, L.; Aganja, R. P.; Napit, R.; Manandhar, K. D.

2026-04-10 immunology 10.64898/2026.04.08.717190 medRxiv
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Dengue disease remains a significant global health threat, with current vaccines exhibiting variable efficacy and safety concerns. Virus-like particles (VLPs) offer a promising alternative by mimicking native virus structures without infectious genomes. We engineered a mammalian expression plasmid encoding Dengue-1 prM and E proteins, optimized for secretion using Japanese Encephalitis virus signal sequences, and transiently expressed it in HeLa cells. Purified VLPs exhibited spherical morphology ([~]39 nm diameter) consistent with native virions, as confirmed by transmission electron microscopy. Immunization of mice with these VLPs elicited robust Dengue-1 specific IgG antibody responses. Our study demonstrates production of immunogenic Dengue-1 VLPs in HeLa cells, highlighting their potential as a vaccine candidate and a tool for serodiagnosis. Further characterization of VLP epitopes and protective efficacy is warranted to advance vaccine development. ImportanceDengue remains a significant global health challenge, with serotype 1 being one of the dominant strains causing recurrent outbreaks in Nepal. Existing vaccines demonstrate limited efficacy and pose significant safety concerns, particularly in seronegative populations. To address these limitations, this study explores virus-like particles (VLPs) as a safer alternative vaccine platform. VLPs elicit robust immunogenicity by mimicking the structure of native virus while completely lacking genetic components. This study combines DENV1 structural proteins with optimized expression systems to enhance immunogenicity. This work is particularly significant as the first dengue vaccine research conducted in Nepal, directly addressing antigenic mismatches between existing commercial vaccines and locally circulating viral strains. Furthermore, the study provides scalable platform for developing region-specific dengue vaccines for other serotypes and flaviviruses.

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Coated Bacterial Vaccine Platform Overcomes Weak Antigen Immunogenicity: A Functional Approach to GnRH-Based Immunocastration

Harguindeguy, I.; Assandri, M.; Daza Millone, A.; Cavalitto, S.; Serradell, M.; Ortiz, G.

2026-04-22 immunology 10.64898/2026.04.20.719670 medRxiv
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Immunocastration, a non surgical strategy based on active immunization against gonadotropin-releasing hormone (GnRH), effectively suppresses steroidogenesis and spermatogenesis. However, peptide vaccines targeting poorly immunogenic antigens such as GnRH often fail to elicit robust adaptive immune responses, requiring adjuvants or carrier proteins. Previously, we introduced Coated Bacterial Vaccines (CBVs), a platform that uses chemically inactivated Gram-positive bacteria to display recombinant antigens fused to the SlpA carboxy terminal domain (dSLPA) on their surface. This system leverages natural pathogen associated molecular patterns (PAMPs) to enhance immunogenicity without additional adjuvants. In this work, we extended the application of the CBVs platform to enhance the immune response against a poorly immunogenic GnRH-based peptide vaccine. GnRH-CBVs were formulated using inactivated Bacillus subtilis var. natto coated with a recombinant GnRH tandem repeat dSLPA fusion protein and administered to male BALB/c mice. A chitosan-adjuvanted GnRH dSLPA formulation served as a positive control. GnRH-CBVs induced a strong Th2-biased humoral response, characterized by predominant IgG1 levels comparable to those achieved with chitosan. The resulting antibodies effectively neutralized endogenous GnRH, reducing steroidogenesis and spermatogenesis and inducing marked testicular histological alterations. These findings support CBVs as a promising strategy to enhance peptide vaccine immunogenicity for veterinary immunocastration.

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Assessing the impact of a gender-neutral approach to HPV vaccination on vaccination coverage for nine-year-old girls in Cameroon: a retrospective, cross-sectional study

Griffith, B. C.; Iliassu, S.; Mbanga, C.; Ngenge, B. M.; Patel, S.; Graves, J. C.; Singh, N.; Ndoula, S.; Njoh, A. A.; Gisele, E.; Mngemane, S.; Ajayi, T.; Zultak, L. A.; Saidu, Y.

2026-04-11 public and global health 10.64898/2026.04.09.26350560 medRxiv
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Cameroon introduced Human papilloma virus vaccine (HPVV) into the routine immunization schedule in October 2020. By the end of 2022, coverage remained low. To increase coverage, Cameroon switched to a country-wide, gender-neutral vaccination (GNV) approach in 2023, coupled with a revamped delivery strategy consisting of Community Dialogues (CDs) and Periodic Intensification of Routine Immunization (PIRIs) activities in selected health districts (HDs). We assessed the impact of these programmatic changes, notably the GNV approach, on HPVV coverage. This retrospective, cross-sectional study measured the effect of GNV and CDs + PIRIs on HPVV coverage among 9-year-old girls in Cameroon (2022-2023). Data on HPVV coverage from all 203 HDs were extracted from DHIS2, and coverage was calculated at the HD level, based on the estimated population eligible of 9-year-old girls. Descriptive statistics and multiple regression models were employed to assess the impact of GNV on vaccination coverage while adjusting for CDs + PIRIs and urban/rural status. In 2023, of the 203 HDs, 115 (56.7%) conducted GNV only, 74 (36.5%) implemented GNV & CDs + PIRIs, and 75.9% (154) were classified as rural. Among age-eligible girls, there was an overall increase in HPV vaccination coverage, with coverage rising 39.2 percentage points from 2022 to 2023. Following multiple linear regression, there was a significant increase in HPVV coverage in HDs with GNV & CDs + PIRIs compared to those with no GNV and no CDs + PIRIs ({beta}:55.5%, 95%CI: 38.7, 72.3, p=0.000). Furthermore, there was a significant increase in HPVV coverage in HDs with GNV only compared to those with no GNV or no CDs + PIRIs ({beta}:28.7%, 95%CI: 12.5, 45.0 p=0.001). Overall, the GNV approach increased HPVV coverage for girls significantly, particularly when implemented alongside CDs + PIRIs.

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Minor Consent state policies and COVID-19 vaccination in adolescents

Litchy, C.; Semprini, J.

2026-04-11 public and global health 10.64898/2026.04.10.26350608 medRxiv
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Background Ever since the COVID-19 vaccine became available, vaccinations in adolescents lagged behind adults. Whether adolescent vaccination rates were higher in states with "Minor Consent" policies remains unknown. Methods We accessed adolescent (aged 12-17) county-level vaccine administration data from the CDC (12/2020-05/2023). Our outcomes were COVID-19 vaccination counts for: 1) initial dose, 2) completed series doses, and 3) booster doses. Panel Poisson regression models with state and time random effects, seasonal fixed effects, log-population offsets, and adult vaccination rates were estimated to calculate incidence rate ratios (IRR), testing the association between residing in a state with a Minor Consent policy and COVID-19 vaccine uptake. Results Overall, for the initial dose and complete series, there was no difference in adolescent COVID-19 vaccination between states with or without Minor Consent policies. However, we found that Minor Consent policies were associated with lower COVID-19 booster doses (IRR = 0.582; 95% CI: 0.409, 0.828; p = 0.0026). This association was not found in urban counties (IRR = 0.867; CI = 0.722, 1.043; p = 0.1295), but only in rural counties (IRR = 0.541; CI = 0.401, 0.730; p < 0.0001). Conclusions Minor Consent policies were not associated with higher adolescent COVID-19 vaccination. Rather, we found that Minor Consent policies were associated with lower adolescent vaccination for booster doses in rural counties. Despite minimal evidence of impact, states continue to implement Minor Consent vaccination policies. Future research should investigate not just other vaccines, but also how Minor Consent policies impact parental trust in public health more broadly.

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Maternal respiratory syncytial virus (RSV) vaccine perceptions amongst pregnant women and mothers of infants and toddlers in England: a qualitative study

Bell, S. L.; Chantler, T.; Passanante, A.; Pryce, J.; Bisset, K.; Letley, L.; Campbell, H.; Paterson, P.

2026-03-30 public and global health 10.64898/2026.03.27.26349494 medRxiv
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Aim: To explore RSV knowledge and awareness, RSV vaccination perceptions and acceptability, and preferences for maternal vaccine delivery and communication amongst pregnant women and mothers of infants and toddlers in England. Methods: Between July and November 2024, semi-structured qualitative interviews were performed with 30 mothers (youngest child under 2 years), two of whom were pregnant with a subsequent child. The study was conducted as a follow-on to a UK Health Security Agency survey of attitudes towards RSV vaccination amongst pregnant and post-partum women in England. Findings: Although most mothers had heard of RSV, mothers with experience in health roles were more likely to understand the potential severity of RSV in infants. Likelihood of maternal RSV acceptance was reported as high, with most mothers considering RSV vaccination as beneficial in protecting infants. Most mothers preferred a hybrid approach to vaccine communication, with information available online (e.g. through the NHS website), via written sources (e.g. NHS produced leaflet), and through talking with midwives. For convenience, most mothers preferred the option of fitting vaccinations within the antenatal midwifery appointment schedule rather than going to general practice for a separate appointment. Conclusion: To support maternal RSV vaccination decision-making and access, women need vaccine information early in pregnancy; information provision through a range of different sources (i.e. online, paper, in-person); and vaccination delivery in a convenient location (i.e. as part of antenatal appointments).

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Safety and immunogenicity of an HIV envelope trimer immunogen that elicits CD4 binding site neutralizing antibody precursors (HVTN 300)

Walsh, S.; Hahn, W. O.; Williams, W. B.; Hyrien, O.; Yu, P.-C.; Parks, K. R.; Edwards, R. J.; Parks, R.; Barr, M.; Polakowski, L. L.; Tindale, I.; Jones, M.; Yurdadon, C.; Burnham, R.; Yeh, C.-H.; Heptinstall, J.; Seaton, K.; Andriesen, J.; Sagawa, Z.; Miner, M. D.; De Rosa, S.; McElrath, M. J.; Corey, L.; Tomaras, G. D.; Montefiori, D. C.; Haynes, B. F.; Mayer, K. H.; Baden, L. R.

2026-04-03 hiv aids 10.64898/2026.03.31.26349761 medRxiv
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Background: Induction of HIV envelope (Env)-specific broadly neutralizing antibodies (bnAbs) is considered a key objective for HIV-1 vaccine development. One approach is to vaccinate with HIV Env immunogens that initially target the naive B cell receptors of a bnAb type and boost with a series of HIV Env variants. We chose a priming immunogen, the CH505 transmitted/founder Env with high affinity for the naive B cell receptor of the prototype CD4 binding site (bs) bnAb lineage, CH103, as a candidate priming immunogen to induce the initial critical step in CD4bs bnAb development. Methods: HVTN 300 is a first-in-human, open-label Phase 1 study evaluating the safety and immunogenicity of a CH505 TF chimeric (ch) Trimer adjuvanted with 3M-052-AF (a TLR7/8 agonist) + Alum. The immunogen is a recombinant, stabilized chimeric Env trimer protein with the N-terminal sequence of CH505 TF gp120 Env transplanted into the BG505 SOSIP sequence. Participants received the adjuvanted protein administered in both deltoid muscles at months 0, 2, 4, 8, and 12. Results: Adults (n=18) aged 18 to 55 were screened at a single site in Boston, USA, and 13 were enrolled. Local and systemic reactogenicity was typically mild to moderate. One participant had severe pain/tenderness, and five participants reported transient severe systemic symptoms at least once. Five participants chose to stop further vaccination due to reactogenicity. No vaccine-related SAEs occurred. Vaccine-specific B-cell response rates reached 100% two weeks post third and fifth vaccinations. Antibody blocking experiments with monoclonal antibodies demonstrated that most participants had antibodies directed to the CD4bs. Four out of 11 participants had serum neutralization signatures for CD4bs bnAb precursors. Conclusions: No safety concerns were identified. The adjuvanted CH505 TF chTrimer elicited serum antibodies capable of CD4bs-mediated neutralization against strains designed to detect early precursors of the CD4bs B-cell lineages. Trial Registration: NCT04915768 Disclosure: Presented in part at HIVR4P 2024, Lima, Peru, October 6-10, 2024

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Effectiveness of 2025-2026 mRNA-1283 and BNT162b2 COVID-19 Vaccines Against COVID-19 Related Hospitalizations and Medically-Attended COVID-19 Among Adults Aged >= 65 years in the United States

Vicic, N.; Bogdanov, A.; Hensler, H.; Ryan, T.; Zeng, N.; Beck, E.; Patry, E.; Bonafede, M.; Araujo, A. B.; Wilson, A.

2026-04-16 infectious diseases 10.64898/2026.04.13.26350772 medRxiv
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Background: The 2025/2026 COVID-19 vaccine season introduced updated formulations targeting the LP.8.1 lineage. This study assessed the absolute vaccine effectiveness (aVE) of mRNA-1283 and BNT162b2 on COVID-19 outcomes in adults aged [&ge;]65 years. Methods: Background: The 2025/2026 COVID-19 vaccine season introduced updated formulations targeting the LP.8.1 lineage. This study assessed the absolute vaccine effectiveness (aVE) of mRNA-1283 and BNT162b2 on COVID-19 outcomes in adults aged [&ge;]65 years. Methods: This retrospective study used linked electronic health record and administrative claims data through Jan 31, 2026. Adults [&ge;]65 years who received the mRNA-1283 or BNT162b2 2025/2026 COVID-19 vaccine were matched to unvaccinated individuals. Inverse probability of treatment weighting was applied to matched cohorts of each vaccine to balance covariates. Each vaccine was evaluated independently against its own unvaccinated comparator group. aVE against COVID-19 related hospitalization and medically-attended COVID-19 was estimated using Cox proportional hazards models; aVE = 100 x (1 - hazard ratio [HR]). Results: We identified 233,072 mRNA-1283 recipients and 422,610 BNT162b2 recipients [&ge;]65 years. The aVE (95% confidence interval) of mRNA-1283 against COVID-19 related hospitalization and medically-attended COVID-19 was 59.3% (39.0%, 72.9%) and 42.0% (35.0%, 48.3%) among adults [&ge;]65 years and 66.9% (45.9%, 79.8%) and 50.2% (42.1%, 57.2%) in [&ge;]75 years, respectively. The aVE of BNT162b2 against COVID-19 related hospitalization and medically-attended COVID-19 was 48.3% (32.4%, 60.5%) and 41.2% (36.2%, 45.8%) in [&ge;]65 years and 45.9% (26.0%, 60.4%) and 44.0% (37.8%, 49.6%) in [&ge;]75 years, respectively. Conclusions: This is the first real-world evidence showing that mRNA-1283 prevents COVID-19-related hospitalizations and medically attended events in vulnerable older adults at highest risk of severe disease. These findings support mRNA-1283 as an important public health tool for reducing the ongoing burden of COVID-19.Results: We identified 233,072 mRNA-1283 recipients and 422,610 BNT162b2 recipients [&ge;]65 years. The aVE (95% confidence interval) of mRNA-1283 against COVID-19 related hospitalization and medically-attended COVID-19 was 59.3% (39.0%, 72.9%) and 42.0% (35.0%, 48.3%) among adults [&ge;]65 years and 66.9% (45.9 %, 79.8%) and 50.2% (42.1%, 57.2%) in [&ge;]75 years, respectively. The aVE of BNT162b2 against COVID-19 related hospitalization and medically-attended COVID-19 was 48.3% (32.4%, 60.5%) and 41.2% (36.2%, 45.8%) in [&ge;]65 years and 45.9% (26.0%, 60.4%) and 44.0% (37.8%, 49.6%) in [&ge;]75 years, respectively. Conclusions: This is the first real-world evidence showing that mRNA-1283 prevents COVID-19-related hospitalizations and medically attended events in vulnerable older adults at highest risk of severe disease. These findings support mRNA-1283 as an important public health tool for reducing the ongoing burden of COVID-19.

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A Live Attenuated Vaccine Candidate against Emerging Highly Pathogenic Cattle-Origin 2.3.4.4b H5N1 Viruses

Mostafa, A.; Ye, C.; Barre, R. S.; Shivanna, V.; Meredith, R.; Platt, R. N.; Escobedo, R. A.; Bayoumi, M.; Castro, E. M.; Jackson, N.; Cupic, A.; Nogales, A.; Anderson, T. J.; Garcia-Sastre, A.; Martinez-Sobrido, L.

2026-03-29 microbiology 10.1101/2025.03.28.646033 medRxiv
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Influenza viruses present a significant public health risk, causing substantial illness and death in humans each year. Seasonal flu vaccines must be updated regularly, and their effectiveness often decreases due to mismatches with circulating strains. Furthermore, inactivated vaccines do not provide protection against shifted influenza viruses that have the potential to cause a pandemic. The highly pathogenic avian influenza H5N1 clade 2.3.4.4b is prevalent among wild birds worldwide and is causing a multi-state outbreak affecting poultry and dairy cows in the United States (US) since March 2024. In this study, we have generated a NS1 deficient mutant of a low pathogenic version of the cattle-origin human influenza A/Texas/37/2024 H5N1, namely LPhTXdNS1, and validated its safety, immunogenicity, and protection efficacy in a prime vaccination regimen against wild-type (WT) A/Texas/37/2024 H5N1. The attenuation of LPhTXdNS1 in vitro was confirmed by its reduced replication in cultured cells and inability to control IFN{beta} promoter activation. In C57BL/6J mice, LPhTXdNS1 has reduced viral replication and pathogenicity compared to WT A/Texas/37/2024 H5N1. Notably, LPhTXdNS1 vaccinated mice exhibited high immunogenicity that reach its peak at weeks 3 and 4 post-immunization, leading to robust protection against subsequent lethal challenge with WT A/Texas/37/2024 H5N1. Altogether, we demonstrate that a single dose vaccination with LPhTXdNS1 is safe and able to induce protective immune responses against H5N1. Both safety profile and protection immunity suggest that LPhTXdNS1 holds promise as a potential solution to address the urgent need for an effective vaccine in the event of a pandemic for the treatment of infected animals and humans.

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Immunogenicity and tolerability of booster typhoid conjugate vaccine (TCV) five to six years after initial dose in Burkinabe Children

Sawadogo, J. W.; Hema, A.; Diarra, A.; Kabore, J. M.; Hien, D.; Kouraogo, L.; Zou, A. R.; Ouedraogo, A. Z.; Tiono, A. B.; Datta, S.; Pasetti, M. F.; Neuzil, K. M.; Sirima, S. B.; Ouedraogo, A.; Laurens, M. B.

2026-04-21 public and global health 10.64898/2026.04.19.26351224 medRxiv
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Typhoid fever remains a significant public health challenge in low- and middle-income countries. In 2018, The World Health Organization recommended a single dose typhoid conjugate vaccine (TCV) for routine immunization in endemic settings; however, evidence guiding booster doses remains limited. Homologous TCV booster doses have demonstrated immune boosting. This study assessed the immunogenicity and safety of a heterologous booster using a Vi capsular polysaccharide-CRM197 TCV (Vi-CRM) administered 5-6 years after primary vaccination with a Vi capsular polysaccharide tetanus toxoid TCV (Vi-TT) in children. Children previously enrolled in a Phase 2 trial were recruited. Participants who had received TCV at 9-11 or 15-23 months were given a Vi-CRM booster at 6-7 years of age (Booster-TCV group), and controls received their first TCV dose at the same age (1st-TCV group). Serum anti-Vi IgG concentrations were measured at baseline and 28 days post-vaccination. Solicited and unsolicited adverse events (AEs) and serious adverse events (SAEs) were recorded. Among 147 children enrolled, 87 received a second and 60 received a first TCV dose. Baseline anti-Vi IgG geometric mean titers (GMT) were higher in the Booster-TCV group (21.5 EU/mL; 95% CI: 17.2-26.8) than in the 1st-TCV group (5.5 EU/mL; 95% CI: 4.5-6.7). At day 28, GMTs rose markedly in both groups: 5140.0 EU/mL (95% CI: 4302.0-6141.3) in the Booster-TCV group and 2084.8 EU/mL (95% CI: 1724.4-2520.5) in the 1st-TCV group. Local reactions and systemic AEs were mild. No SAEs were observed. Vi-TT-induced immunity persisted for at least 5-6 years, and a heterologous booster triggered a strong immune response with universal seroconversion. These findings support heterologous prime-boost strategies to maintain protection in school-age children and inform optimization of TCV schedules in endemic regions.

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Economic Burden and Return on Investment of Immunization Programs in Saudi Arabia: A Health Economic Evaluation

Alshahrani, A. M.; Ashour, A. m.

2026-04-17 public and global health 10.64898/2026.04.15.26350984 medRxiv
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Background Vaccine-preventable diseases (VPDs) continue to impose a significant health and economic burden globally, despite advances in immunization programs. Narrower to the context of Saudi Arabia, the current literature consistently shows that the high vaccination coverage has had the primary impact of reducing disease incidence. Regardless, the broader economic impact of VPDs and the financial benefits of immunization remain important for policy evaluation within Saudi Arabia. Methods This study employed a model-based economic evaluation using a societal perspective in order to carry out an estimation of the economic burden of measles, influenza, and pneumococcal diseases. We utilized the Cost of Illness (COI) approach for the purpose of quantifying direct medical costs and indirect productivity losses. On the other hand, the Value of Statistical Life (VSL) approach helped in the estimation of the monetary value of mortality reduction. A comparative framework analyzed current vaccination coverage against a counterfactual no-vaccination scenario for the calculation of the return on investment (ROI). Results The estimated annual economic burden of the three selected VPDs in the absence of vaccination was USD 385 (95% CI: 315-460) million. Immunization programs generated substantial economic benefits, with total benefits estimated at USD 1085 (95% CI: 815-1360) million annually. The calculated ROI was 9.0 (95% CI: 6.8-11.3), essentially an indication that for each dollar invested in vaccination, there was multiple economic returns yielded. Sensitivity analyses confirmed the robustness of these findings. Conclusion Immunization programs in Saudi Arabia provide significant economic and public health benefits and for this reason, sustained investment in vaccination is fundamentally essential towards the reduction of disease burden, improve population health, and ultimately support long-term economic productivity.

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VYD2311 is a promising candidate for passive immunization against COVID-19 in immunocompromised individuals

Mellis, I. A.; Wu, M.; Daniel, K.; Hong, H.; Guo, Y.; Ho, D. D.

2026-04-01 microbiology 10.64898/2026.03.31.715419 medRxiv
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For millions of immunocompromised individuals, vaccines may not elicit adequate protection from infections, so alternative strategies for pre-exposure prophylaxis are essential. There is only one non-vaccine product authorized in the U.S. as pre-exposure prophylaxis against COVID-19: the monoclonal antibody pemivibart. We previously showed that pemivibart had lower neutralizing activity in vitro against many recent dominant SARS-CoV-2 variants, such as KP.3.1.1, NB.1.8.1, and LP.8.1.1, than it had against JN.1, which was dominant when the antibody was first authorized. The manufacturer of pemivibart (Invivyd) recently initated clinical testing of a new monoclonal antibody derived from pemivibart, VYD2311, but there are no available studies of the activity of VYD2311 against dominant and emerging SARS-CoV-2 variants. Here, using pseudovirus neutralization assays, we measured the neutralizing activity of laboratory-synthesized VYD2311 and pemivibart against dominant and emerging SARS-CoV-2 variants, including XFG, NB.1.8.1, and the genetically distant BA.3.2.2. We found that VYD2311 potently neutralized all tested variants in vitro, dramatically more so than pemivibart. Combined with interpretation of earlier clinical trials of a parental antibody product, we conclude that VYD2311 is a promising candidate for passive immunoprophylaxis against COVID-19, particularly for those who do not respond well to vaccination.

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Assessment of Repurposed Compounds for Antiviral Activity Against Measles Virus

Rossler, A.; Ayala-Bernot, J.; Mohammadabadi, S.; Lasrado, N.; Warke, S.; Flaumenhaft, R.; Barouch, D.

2026-04-01 microbiology 10.64898/2026.03.31.715719 medRxiv
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BackgroundThere is currently no approved antiviral therapy against measles virus (MeV). Repurposing available compounds with broad antiviral activity may rapidly identify candidate drugs for clinical evaluation. Here we evaluated the antiviral activity of the clinically approved drugs azelastine hydrochloride and zafirlukast as well as the flavonoids quercetin and isoquercetin against MeV in preventative and therapeutic in vitro studies. MethodsCompounds were tested for antiviral activity against MeV in preventative (prophylactic and virucidal) and therapeutic (steady-state and persistent) assays in Vero/hSLAM cells. Viral loads and cell viability were measured 48h post-infection, and dose-response curves were used to calculate EC50 values. Flavonoids were also tested in the presence of 1 mM ascorbic acid. ResultsAzelastine hydrochloride did not show evidence of antiviral activity against MeV under these conditions, whereas zafirlukast, quercetin, and isoquercetin showed therapeutic activity against MeV. The addition of ascorbic acid enhanced the therapeutic potency of quercetin to 4.2-4.8 {micro}M and of isoquercetin to 10.7-10.9 {micro}M. Antiviral activity was dose-dependent when administered post-infection. ConclusionAmong the four compounds tested, quercetin showed the most potent therapeutic antiviral activity against MeV in vitro. Isoquercetin and zafirkulast also showed therapeutic activity. These findings support further evaluation of quercetin, isoquercetin, and zafirlukast as candidate antiviral drugs for MeV and highlight the utility of in vitro platforms for rapid antiviral drug screening.

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Attitudes towards new tuberculosis vaccines among adults, adolescents and their caregivers in southern Mozambique, 2024

Lima, A.; Campos, I.; Kim, D.; Shiiba, M.; Cranmer, L. M.; Acacio, S.; Garcia-Basteiro, A. L.; Vasudevan, L.; Nelson, K. N. B.

2026-04-01 infectious diseases 10.64898/2026.03.30.26349798 medRxiv
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New tuberculosis (TB) vaccines for adults and adolescents could transform TB prevention programs, but their impact depends on successful implementation. We investigated willingness to be vaccinated with a new TB vaccine in a high HIV and TB burden setting in southern Mozambique in 2024 using a mixed methods approach involving a cross-sectional survey and concurrent in-depth interviews. In 151 surveys and 23 interviews, we found that willingness to receive a new TB vaccine among adults and adolescents was 77% (148/192) overall. In multivariable analysis, adolescents were more willing to receive a new TB vaccine than adults even when adjusting for other factors which may influence vaccination decisions (adjusted OR: 5.6, 95% CI: 1.7-17.7). Personal experience with TB and greater knowledge of the disease was also linked with willingness to be vaccinated. Qualitative findings reinforced quantitative findings, further clarifying that even among those who expressed hesitancy, a safe and effective TB vaccine endorsed by healthcare workers, government agencies, and community leaders would likely have high uptake. Our findings are specific to southern Mozambique and can shape vaccine introduction efforts after a TB vaccine is licensed and approved for use in this age group.

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Accessibility and regional disparities in nationwide 24-hour home medical care: A quantitative evaluation using the enhanced two-step floating catchment area method

Egashira, Y.; Watanabe, R.

2026-04-20 health policy 10.64898/2026.04.18.26351162 medRxiv
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With Japans rapidly aging population, demand for home healthcare is projected to increase by 62% by 2040. This study quantitatively evaluated accessibility to 24-hour home healthcare and regional disparities across all 335 secondary medical areas (SMAs) in Japan using the Enhanced Two-Step Floating Catchment Area (E2SFCA) method. We conducted a nationwide cross-sectional study analyzing approximately 430,000 population points at 500-meter mesh resolution. The E2SFCA integrated demand (age-adjusted population), supply (24-hour home care support clinics and hospitals), and transportation (road networks). Accessibility scores (ASs) and Gini coefficients were calculated for each SMA. Wards hierarchical cluster analysis classified regional types, and multiple regression based on the Penchansky and Thomas five-dimensional access framework identified factors associated with the median AS (ASM) and Gini coefficient. The median ASM was 45.71 (0.00-153.49), and the median Gini coefficient was 0.33 (0.06-0.93). Cluster analysis identified six types ranked by descending ASM, from C1 (high access, equitable; n = 48) to C6 (access desert; n = 23). C6 had a median ASM of 0.00 and Gini coefficient of 0.74, indicating virtually no access within a 30-minute catchment. Home-visit standardized claim ratios, used as external validation, declined monotonically from C1 (125.6) to C6 (17.6). For ASM, 24-hour visiting nursing stations ({beta} = +0.369) and clinic physicians ({beta} = +0.342) showed the strongest positive associations, with non-residential area negatively associated ({beta} = -0.273). For the Gini coefficient, non-residential area showed the strongest positive association ({beta} = +0.523). Taxable income per taxpayer was not significantly associated with either outcome. Non-residential area was associated with both lower accessibility and greater intra-regional inequality, suggesting that geographic constraints may limit the effectiveness of resource investment alone. Uniform nationwide implementation of policies shifting care from long-term care beds to home healthcare may not be feasible; region-specific approaches considering geographic characteristics are necessary.

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Implementation of SMS and voice message reminders to reduce childhood immunization dropout rate in urban settings: A Pilot Study in Lome-Togo in 2026

Badarou, S.; Attah, K. M.; Gounon, K. H.; Dali, A. S.; Sire, X. R.; Dia, E. C.

2026-04-20 public and global health 10.64898/2026.04.19.26350799 medRxiv
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ObjectiveThis study aimed to assess the effectiveness of SMS and voice message reminders in reducing the dropout rate in Lome-Togo, in 2026. MethodsWe conducted a cross-sectional study between October 2025 and March 2026 in the Grand Lome region. The intervention consisted of an integrated digital system used by health facilities to send automated SMS. Categorical variables were described in terms of frequency and proportion; Fishers exact test was used to compare proportions. Quantitative variables were described by their means accompanied by their standard deviation; the Wilcoxon rank-sum test was used to compare means. The significance level for statistical tests was set at 5%. ResultsA total of 30 health facilities were included. Seventy percent (70.0%) of the health facilities used messages associated with calls. Ninety percent (90.0%) of participants found the reminders useful, and 60.0% reported an improvement in Expanded Program on Immunization services related to their use. Among participants who received a reminder, 51.0% kept their vaccination appointments. The Penta 1/3 dropout rate decreased from 3.2% before the intervention to 1.3% (p < 0.001). Among the 323 parents of children included, only 20.74% reported receiving a reminder by phone. Sixty-point-five percent (60.5%) preferred to receive both text messages and voice calls. ConclusionThis study demonstrates the operational feasibility of an SMS/call-based reminder system in reducing dropout rate for childhood vaccination in Togo.

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Factors Associated with Malaria Vaccine Hesitancy Among Caregivers of Children 6-59 Months, In Ugenya Sub County, Siaya County, Kenya: A cross - Sectional Mixed Study

Ochieng', E. A.; Muita, J. W.; Olewe, T.

2026-04-23 public and global health 10.64898/2026.04.21.26351425 medRxiv
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ABSTRACT Background: Malaria remains a leading public health burden in sub-Saharan Africa, disproportionately affecting children under five years. In response, Kenya introduced the RTS,S/AS01 malaria vaccine in selected regions, including Siaya County where malaria transmission is endemic. Despite this milestone, uptake has been inconsistent, with hesitancy emerging as a significant barrier. Objective: This study aimed to determine factors associated with malaria vaccine hesitancy among caregivers of children 6-59 months in Ugenya Subcounty, Siaya County. Methodology: A cross-sectional mixed methods design was employed involving 425 caregivers and 15 healthcare workers and County health officials between January to February 2025. Quantitative data were collected using structured questionnaires and analyzed in Stata version 17 through descriptive statistics, bivariate analysis at 20% significance threshold, and multivariable logistic regression at 5% level to determine key factors associated with malaria vaccine hesitancy. Qualitative data from 15 key informant interviews were transcribed verbatim and thematically analyzed using NVivo. Thematic analysis, guided by a predefined codebook, was used to identify recurring patterns and extract key themes, which were illustrated with direct quotations from participants Results: Overall, 42.9% of caregivers (n=181; 95% CI: 38.9%-47.3%) reported hesitancy. Significant predictors included caregiver age, marital status, family size, access to health facilities, and vaccine availability. Single caregivers, those from smaller households, and those facing health facility access challenges were more likely to be hesitant to malaria vaccine. Despite high levels of knowledge, misconceptions and misinformation about vaccine safety, often spread via social media persisted. Conversely, caregivers relying on healthcare workers and mainstream media showed greater acceptance of malaria vaccine. Conclusion and Recommendations: Malaria vaccine hesitancy remains significant at 42.9%, driven by demographic factors such as younger age, single status, and smaller household size. Structural barriers including limited vaccine availability and poor access to health facilities further contribute to reluctance. Although knowledge and awareness were high, misinformation, particularly from social media, persisted, while information from healthcare workers improved acceptance. Addressing these gaps through targeted community engagement, improved access, and trusted communication channels is essential to increase uptake of malaria vaccine.

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Linguistic Validation of the Rett Syndrome Behavior Questionnaire Spanish Translation: a Two-Stage Caregiver Study Across Latin America

Polo Sanchez, M.; Lesmes, A. C.; Muni, N.; Vigneault, F.; Novak, R.

2026-04-23 neurology 10.64898/2026.04.16.26349544 medRxiv
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Background: Rett Syndrome (RTT) is a severe neurodevelopmental disorder affecting approximately 1 in 10,000 live female births worldwide. The Rett Syndrome Behaviour Questionnaire (RSBQ), remains one of the most widely used standardized behavioral assessment tools for RTT. However, the RSBQ was originally validated only in British English, limiting its applicability for Spanish-speaking caregivers and clinical centers across Latin America and Spain. Objective: The primary aim of this study was to develop and validate the comprehension of the Spanish translation of the RSBQ to ensure cultural and linguistic equivalence, enhance data reliability, and facilitate earlier, more accurate clinical assessments among Spanish-speaking RTT populations. Methods: Surveys were administered in two phases to Spanish-speaking caregivers between November 2023 and September 2025. Phase I consisted of 12 guided survey administrations with participants being able to ask clarifying questions and offer linguistic modifications of RSBQ questions. Phase II consisted of independent online administration of the refined Spanish RSBQ and a retest at least 7 days later. Participants were recruited through direct outreach and supported virtually during questionnaire completion. Results: Following data cleaning and quality control, a total of 51 caregivers successfully completed both surveys. The Spanish RSBQ demonstrated high caregiver comprehension and strong engagement across multiple Latin American countries, including Argentina, Mexico, and Peru. Responses were highly correlated between test and retest timepoints, and no question showed biased response distributions. A slight effect of response interval on test-retest correlation was observed, potentially indicating the impact of natural disease progression confounding retest evaluation for long (>80 day) intervals; however this effect did not impact the overall linguistic validation results as analysis of only <21 day test-retest responders confirmed the findings. Conclusions: This linguistic validation study represents the first formal step toward the clinical validation of the Spanish RSBQ, enabling broader inclusion of Spanish-speaking populations in RTT research. The collaborative, bilingual data collection strategy proved both feasible and effective, paving the way for multinational trials and expanding therapeutic accessibility through localized, patient-centered innovation.