#Statement on the #antigen #composition of #COVID19 #vaccines (#WHO, May 16 '26)

 

Key points:

    -- The WHO Technical Advisory Group on COVID-19 Vaccine Composition (TAG-CO-VAC) held its twice-yearly decision-making meeting in May 2026 to review the evolution of SARS-CoV-2, the effectiveness of currently approved COVID-19 vaccines and the implications for COVID-19 vaccine antigen composition.

    -- The objective of any update to COVID-19 vaccine antigen composition is to enhance vaccine-induced immune responses to circulating SARS-CoV-2 variants, when needed.

    -- Following this meeting, the TAG-CO-VAC advises vaccine manufacturers that monovalent LP.8.1 is the recommended vaccine antigen.

    -- Other antigens (e.g. XFG, NB.1.8.1) or other approaches that demonstrate broad and robust neutralizing antibody responses or efficacy against currently circulating SARS-CoV-2 variants could also be used.

    -- Vaccination remains an important public health countermeasure against COVID-19 and vaccination should not be delayed in anticipation of access to vaccines with an updated antigen composition. As per the March 2026 WHO Strategic Advisory Group of Experts on Immunization (SAGE) recommendations, Member States should consider routine COVID-19 vaccination of groups at highest risk of severe COVID-19 disease.

    -- The WHO Technical Advisory Group on COVID-19 Vaccine Composition (TAG-CO-VAC) continues to closely monitor the genetic and antigenic evolution of SARS-CoV-2 variants, immune responses to SARS-CoV-2 infection and COVID-19 vaccination, and the effectiveness of COVID-19 vaccines against circulating variants. 

    -- Based on these evaluations, WHO advises vaccine manufacturers and regulatory authorities on the implications for future updates to COVID-19 vaccine antigen composition. 

    -- In December 2025, the TAG-CO-VAC advised vaccine manufacturers that monovalent LP.8.1 is the recommended vaccine antigen. Multiple manufacturers (using mRNA or recombinant protein-based vaccines) have updated COVID-19 vaccine antigen composition to monovalent LP.8.1 formulation. Several of these vaccines have been approved for use by regulatory authorities and have been introduced into vaccination programmes. Previous statements from the TAG-CO-VAC can be found on the WHO website.

    -- The TAG-CO-VAC reconvened on 7-8 May 2026 to review the genetic and antigenic evolution of SARS-CoV-2; immune responses to SARS-CoV-2 infection and/or COVID-19 vaccination; the effectiveness of currently approved vaccines against circulating SARS-CoV-2 variants; and the implications for COVID-19 vaccine antigen composition.

Evidence reviewed

    -- The published and unpublished evidence reviewed by the TAG-CO-VAC included: 

    (1) SARS-CoV-2 genetic evolution, with additional support from the WHO Technical Advisory Group on Virus Evolution (TAG-VE); 

    (2) Antigenic characterization of previous and emerging SARS-CoV-2 variants using virus neutralization tests with animal antisera and further analysis of antigenic relationships using antigenic cartography; 

    (3) Immunogenicity data on the breadth of neutralizing antibody responses elicited by currently approved vaccine antigens against circulating SARS-CoV-2 variants using animal and human sera, with additional support from WHO Coronavirus Network (CoViNet); 

    (4) Preliminary clinical immunogenicity data on immune responses following infection with circulating SARS-CoV-2 variants; 

    (5) Available COVID-19 vaccine effectiveness (VE) estimates of currently approved vaccines; and 

    (6) Preliminary non-clinical and clinical immunogenicity data on the performance of candidate vaccines with updated antigens shared by vaccine manufacturers with TAG-CO-VAC. 

    Further details on the data reviewed by the TAG-CO-VAC can be found in the accompanying data annex. Confidential data reviewed by the TAG-CO-VAC are not shown.

Summary of available evidence

    There are persistent and increasing gaps and delays in the surveillance and reporting of cases, hospitalizations and deaths from WHO Member States, limiting the interpretation and comparability of epidemiological trends over time. 

    In 2026, SARS-CoV-2 continues to circulate globally, causing severe disease, post COVID-19 condition, and death. 

    However, the impact on health systems has reduced substantially compared to 2020-2021 due to multiple factors, including increased population immunity from infection and/or vaccination and improved clinical management. 

    In 2026, all WHO regions are reporting lower SARS-CoV-2 test positivity rates than during the corresponding period in previous years.

    Globally, the current predominant variant among SARS-CoV-2 sequences remains Variant Under Monitoring (VUM) XFG, however the weekly proportion is now declining. 

    In contrast, in countries in the WHO Western Pacific Region where sequencing continues, VUM NB.1.8.1 is the predominant variant. 

    Globally, the proportion of VUM BA.3.2 is increasing, with heterogeneous dynamics across countries where genomic surveillance continues. 

    BA.3.2 appears to have lower fitness than JN.1-descendant variants, which may explain why BA.3.2 has not displaced JN.1-descendant variants in regions where it has been detected. 

    To date, the increase in the proportion of BA.3.2 does not appear to be associated with a substantial increase in disease burden, unlike increases associated with previous Variants of Interest and JN.1-descendant variants. 

    In several countries, BA.3.2 appears to account for a higher proportion of sequences from young children than adults, suggesting possible differences in susceptibility to BA.3.2 related to a lack of cross-reactive immunity generated by previous exposure to early SARS-CoV-2 variants. 

    However, sequence numbers and the reported number of infected individuals, including those with severe disease, remain low; this observation should therefore be interpreted with caution.

    Neutralization data using antisera from naïve animals infected or vaccinated with JN.1, LP.8.1, NB.1.8.1 or XFG, indicated that recent JN.1-descendant variants are antigenically closely related. 

    These variants differed by approximately 1 antigenic unit in cartographic analyses, corresponding to a two-fold-difference in neutralization, with XFG often the most antigenically distant from JN.1 within the JN.1 cluster. 

    In contrast, these antisera showed limited neutralizing activity against BA.3.2. 

    Antisera from naïve animals infected with BA.3.2 showed very limited cross-reactivity with recent JN.1-descendant variants. 

    Together, these results indicate that BA.3.2 is antigenically distinct from JN.1- descendant variants.

    Sera from cohorts that are representative of recent population immunity and pre-LP.8.1 vaccination sera demonstrated cross-reactivity with recent JN.1-descendant variants and with BA.3.2.

    Pre- and post-vaccination sera from individuals immunized with LP.8.1 demonstrated significant increases in neutralizing activity against JN.1 and its descendant variants, including NB.1.8.1 and XFG. 

    Post-vaccination neutralizing antibody titers and the fold change against BA.3.2 were lower than against the homologous LP.8.1 antigen and other JN.1- descendant variants.

    Pre- and post-vaccination sera from individuals immunized with JN.1 or KP.2 demonstrated significant increases in neutralizing activity against JN.1 and its descendant variants. 

    However, post-vaccination neutralizing antibody titers against NB.1.8.1 and XFG were lower than those against the homologous JN.1 or KP.2 antigens, with even larger reductions typically observed for BA.3.2.

    Contemporary vaccine effectiveness (VE) estimates are relative (rVE) and demonstrate the added or incremental protection of recent vaccination over and above pre-existing infection- and vaccine-derived immunity. 

    Monovalent JN.1 and KP.2 mRNA vaccines demonstrated additional protection—relative to pre-existing immunity—against symptomatic and severe COVID-19. 

    The limited number of rVE estimates using monovalent LP.8.1 vaccines also demonstrated additional protection against symptomatic and severe COVID-19.

    Data shared with the TAG-CO-VAC by vaccine manufacturers showed that:

      - Immunization of naïve mice with monovalent LP.8.1, XFG or NB.1.8.1 induced high neutralizing antibody titers against the homologous antigen, as well as other JN.1-descendant variants. 

    - Low or non-detectable neutralizing antibody titers were consistently observed against BA.3.2. 

    - In contrast, immunization of naïve mice with monovalent BA.3.2 induced immune responses largely restricted to the homologous antigen. 

    - Overall immunogenicity of BA.3.2 was lower than after LP.8.1, XFG or NB.1.8.1 immunization.

    - Immunization of mice previously immunized with SARS-CoV-2 variants and then immunized with LP.8.1, XFG or NB.1.8.1 induced high neutralizing antibody titers against JN.1-descendant variants. 

    - Lower neutralizing antibody titers against BA.3.2 were observed. 

    - Immunization with BA.3.2 induced neutralizing titers against the homologous antigen, and to a lesser extent against JN.1-descedant variants. 

    - However, overall immunogenicity of BA.3.2 was lower than after LP.8.1, XFG or NB.1.8.1 immunization.

    - In humans, vaccination with 8.1 induced strong increases in neutralizing antibody titers against JN.1, LP.8.1, NB.1.8.1 and XFG. 

    - As in mice, post- vaccination neutralizing antibody titers against BA.3.2 were lower than those against the homologous LP.8.1 antigen. 

    - A single clinical immunogenicity study using a BA.3.2 vaccine candidate showed increased neutralizing antibody titers against the homologous antigen, and a back boost against JN.1-descendant variants, but overall lower immunogenicity than the LP.8.1 vaccine.

    - Overall, LP.8.1 as a vaccine antigen in populations with high levels of prior infection and / or vaccination continues to induce broadly cross-reactive immune responses to circulating SARS-CoV-2 variants.

    -- The TAG-CO-VAC acknowledges several limitations of available data:

    - There are persistent and increasing gaps and delays in the reporting of cases, hospitalizations and deaths, from WHO Member States, as well as in genetic/genomic surveillance of SARS-CoV-2 globally, including low numbers of samples sequenced and limited geographic diversity. The TAG-CO-VAC strongly supports the ongoing work of the WHO Coronavirus Network (CoViNet) and the Global Influenza Surveillance and Response System (GISRS) to address this information gap.

    - The timing, specific mutations and antigenic characteristics of emerging and future variants are difficult to predict, and the potential public health impact of these variants remain unknown. Currently, two antigenically distinct lineages (JN.1-descendant and BA.3.2-descendant variants) are circulating and the comparative evolutionary potential of these lineages remains uncertain. Variants derived from these lineages will continue to be monitored and/or characterized, and the TAG-CO-VAC strongly supports the ongoing work of the TAG-VE. 

    - Although neutralizing antibody titers have been shown to be important correlates of protection from SARS-CoV-2 infection and of estimates of vaccine effectiveness, there are multiple components of immune protection elicited by infection and/or vaccination. Data on the immune responses following JN.1-descendant variant infection or monovalent LP.8.1 vaccination are largely restricted to neutralizing antibodies. Data and interpretation of other aspects of the immune response, including cellular immunity, are limited. 

    - Immunogenicity data against currently circulating SARS-CoV-2 variants are not available for all COVID-19 vaccines. 

    - Recent estimates of rVE are limited in terms of the number of studies, geographic diversity, vaccine platforms evaluated, populations assessed, duration of follow-up, and contemporary comparisons of vaccines with different antigen composition. There are currently only a limited number of available rVE estimates using monovalent LP.8.1 mRNA vaccines; there are no rVE estimates in populations in which BA.3.2 was the predominant variant.

Recommendations for COVID-19 vaccine antigen composition

    -- Monovalent LP.8.1 (Nextstrain: 25A; GenBank: PV074550.1; GISAID: EPI_ISL_19467828) is the recommended COVID-19 vaccine antigen.

    -- Other antigens (e.g. XFG, NB.1.8.1) or other approaches that demonstrate broad and robust neutralizing antibody responses or efficacy against currently circulating SARS-CoV-2 variants could also be used.

    -- As per the March 2026 WHO Strategic Advisory Group of Experts on Immunization (SAGE) recommendations, Member States should consider routine COVID-19 vaccination of groups at highest risk of severe COVID-19 disease and vaccination should not be delayed in anticipation of access to vaccines with an updated antigen composition.

Further data requested

    -- Given the limitations of the evidence upon which the recommendations above are derived and the anticipated continued evolution of the virus, the TAG-CO-VAC strongly encourages generation of the following data (in addition to the types of data outlined in March 2026)

    - Immune responses and clinical endpoints (i.e. VE and/or comparator rates of infection and severe disease) in varied human populations who receive currently approved COVID-19 vaccines against emerging SARS-CoV-2 variants, across different vaccine platforms.

    - Strengthened epidemiological and virological surveillance, as per the Standing Recommendations for COVID-19 in accordance with the International Health Regulations (2005), to determine if emerging variants are antigenically distinct and able to displace circulating variants.

    - Strengthened epidemiological surveillance to characterize disease severity in immunologically naïve and/ or immature individuals (e.g. young pediatric cohorts), particularly for BA.3.2 infections.

    - Non-clinical and clinical immunogenicity data against circulating SARS-CoV-2 variants for vaccine candidates with different SARS-CoV-2 antigens.

    - As previously stated, the TAG-CO-VAC continues to encourage the further development of vaccines that may improve protection against infection and reduce transmission of SARS-CoV-2.

    -- The TAG-CO-VAC will continue to closely monitor the genetic and antigenic evolution of SARS-CoV-2 variants, immune responses to SARS-CoV-2 infection and COVID-19 vaccination, and the effectiveness of COVID-19 vaccines against circulating variants. The TAG-CO-VAC will also continue to reconvene every six months, or as needed, to evaluate the implications for COVID-19 vaccine antigen composition. At each meeting, recommendations to either maintain current vaccine composition or to consider updates will be issued. Prior to each meeting, the TAG-CO-VAC will publish an update to the statement on the types of data requested to inform COVID-19 vaccine antigen composition deliberations.

Source: 

Link: https://www.who.int/news/item/16-05-2026-statement-on-the-antigen-composition-of-covid-19-vaccines

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Membrane-anchored #influenza #neuraminidase vaccine drives #human-like broadly protective B cell responses

 

Abstract

Influenza neuraminidase (NA) is a promising target for universal flu vaccines, yet eliciting potent B-cell responses against its conserved epitopes remains challenging. Here, we developed a membrane-anchored, folding-domain-free NA (mNA) that elicited superior head-specific germinal center B cell and antibody responses compared to soluble tetrameric NA. In non-human primates, mNA immunization induced cross-reactive memory B cell (MBC) responses, expanding clones with the conserved DR motif in HCDR3, a hallmark of human broadly reactive NA antibodies. These MBCs conferred cross-inhibitory activity against diverse NA variants and in vivo cross-protection. Cryo-EM analysis revealed that the 554-C2 clone targets the conserved enzymatic pocket via the DR motif, while the 554-C1 clone recognizes previously uncharacterized epitopes at the interface between two adjacent N2 monomers, effectively reducing plaque formation by contemporary H3N2 strains. Our findings highlight the immunological advantages of membrane-anchoring, providing a robust strategy for designing next-generation vaccines against influenza and other pathogens.

Competing Interest Statement

Westlake University has filed for patent protection for mNA used as an influenza vaccine.

Funder Information Declared

State Key Laboratory of Gene Expression, SKLGE-ZX-2025007

Zhejiang Provincial Key Laboratory Construction Project, 2024ZY01026, 2024E10060, 2024E10052

Natural Science Foundation of Zhejiang province, LR26H190001

National Natural Science Foundation of China, 82471855, 825B2062, 82330054, 82502209, 32471303

Source: 

Link: https://www.biorxiv.org/content/10.64898/2026.05.13.724804v1

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The Decline in #Influenza #Antibody Titers and Modifiers of #Vaccine #Immunity from over Ten Years of Serological Data

 

Abstract

Annual influenza vaccination is the cornerstone for seasonal protection, yet antibody responses are highly variable across individuals and over time. To systematically assess the determinants of this heterogeneity, we compiled 20,449 hemagglutination inhibition and neutralization titers from 4,540 participants enrolled in 14 new vaccine studies we conducted and 50 prior studies that collectively span 2010-2023. Seasonal effects dominated, with pre- and post-vaccination titers declining steadily from 2017 onwards, outweighing the influence of age, sex, or repeated vaccination. Titers to B Yamagata remained steady throughout all years examined, suggesting unique durability and offering a reason for lineage extinction. Vaccine timing emerged as a strong and previously underappreciated determinant of immunity, with individuals vaccinated later in the season exhibiting larger post-vaccination titers. Not being vaccinated or receiving the live-attenuated FluMist vaccine in one year significantly enhanced the response to inactivated vaccines in 45% or 68% of cohorts, respectively, whereas antigen dose and adjuvants had modest impact. These findings identify vaccine timing and seasonal context as underrecognized drivers of immunogenicity and provide actionable insights for optimizing influenza vaccination strategies.

Competing Interest Statement

The authors have declared no competing interest.

Funding Statement

This research was supported by the the National Institute of Allergy and Infectious Diseases (NIAID) of the National Institutes of Health (NIH) under the Computational Models of Influenza Immunity (U01 AI187062), LJI & Kyowa Kirin, Inc. (KKNA - Kyowa Kirin North America), and the Bodman family (TE).

Source: 

Link: https://www.medrxiv.org/content/10.64898/2026.01.07.25342310v2

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Efficacy and #Safety of an #mRNA Seasonal #Influenza #Vaccine in Adults

 

Abstract

Background

Seasonal influenza causes substantial illness and death in adults 50 years of age or older, even with current vaccines. An investigational messenger RNA (mRNA)–based vaccine called mRNA-1010 encodes hemagglutinin glycoproteins from World Health Organization–recommended influenza strains.

Methods

In this phase 3, double-blind, active-controlled trial, we randomly assigned adults 50 years of age or older to receive trivalent mRNA-1010 (37.5 μg, which includes 12.5 μg of each strain) or a licensed standard-dose comparator. The primary efficacy end point was relative vaccine efficacy against reverse-transcriptase–polymerase-chain-reaction (RT-PCR)–confirmed, protocol-defined influenza-like illness caused by influenza A or B, from at least 14 days after vaccination through the end of the influenza season. Hypothesis testing was conducted hierarchically to assess noninferiority (lower boundary of the 95% confidence interval [CI], >−10%), superiority (lower boundary of the 95% CI, >0%), and a higher level of superiority (lower boundary of the 95% CI, >9.1%).

Results

A total of 40,703 participants received mRNA-1010 (20,350 participants) or the standard-dose comparator (20,353 participants); the median follow-up was 181 days (range, 1 to 227). RT-PCR–confirmed, protocol-defined influenza-like illness was observed in 411 of 20,179 recipients of mRNA-1010 (2.0%) and 557 of 20,124 recipients of the standard-dose comparator (2.8%), which corresponds to a relative vaccine efficacy of 26.6% (95% CI, 16.7 to 35.4), thereby meeting the criteria for noninferiority, superiority, and higher-level superiority. Solicited adverse reactions were more frequent with mRNA-1010 than with the standard-dose comparator (injection-site pain in 65.8% vs. 29.8%, fatigue in 45.1% vs. 20.3%, headache in 37.8% vs. 18.0%, and myalgia in 35.4% vs. 11.6%); most reactions were mild to moderate and transient. Serious adverse events were reported in 2.2% of the recipients of mRNA-1010 (with three events considered by the investigator to be vaccine-related) and in 1.9% of the recipients of the standard-dose comparator (with two events considered by the investigator to be vaccine-related).

Conclusions

In this trial, mRNA-1010 was superior to standard-dose licensed vaccines for prevention of RT-PCR–confirmed, protocol-defined influenza-like illness in adults 50 years of age or older. Solicited adverse reactions were more frequent with mRNA-1010. (Funded by Blackstone Life Sciences and Moderna; Fluent ClinicalTrials.gov number, NCT06602024.)

Source: 

Link: https://www.nejm.org/doi/full/10.1056/NEJMoa2516491?query=TOC

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Evaluation of Cross-Immunogenicity of #Ferret #Antisera Following Immunization with #H5N1 #Vaccine Strains

 

Abstract

Background: 

Highly pathogenic avian influenza H5N1 viruses of clade 2.3.4.4b have spread globally since 2021, causing extensive outbreaks in avian populations and repeated spillovers into diverse mammalian hosts, including humans. These cross-species transmission events highlight ongoing pandemic risks and underscore the need for vaccine strategies that reflect viral evolution at the human–animal interface. Despite the availability of licensed H5 vaccines and newly recommended World Health Organization (WHO) candidate vaccine viruses (CVVs), the extent to which these vaccines elicit cross-reactive antibody responses against contemporary clade 2.3.4.4b viruses, including mammalian spillover isolates of avian origin, remains incompletely characterized. 

Method: 

In this study, ferret antisera were generated using four WHO-recommended H5 CVVs, including a clade 1 strain (A/Vietnam/1194/2004) and three clade 2.3.4.4b strains (A/Astrakhan/3212/2020, A/American wigeon/South Carolina/22-000345-001/2021, and A/Ezo red fox/Hokkaido/1/2022), formulated with alum adjuvant to reflect licensed vaccine formulation used in national preparedness programs. Antibody responses and cross-reactive activity were evaluated using hemagglutination inhibition (HI) and microneutralization (MN) assays against homologous vaccine strains and a feline-origin clade 2.3.4.4b H5N1 field isolate from Korea, A/Feline/Korea/SNU-01/2023. 

Results: 

Antisera induced by clade 2.3.4.4b CVVs showed cross-reactive antibody responses against homologous and heterologous clade 2.3.4.4b viruses and demonstrated measurable HI and MN responses against the feline-origin field isolate. In contrast, antisera raised against the clade 1 Vietnam CVV exhibited limited cross-reactivity against clade 2.3.4.4b viruses. Overall, clade 2.3.4.4b CVVs generally showed higher antibody responses than the clade 1 vaccine strain across multiple panels. 

Conclusions: 

These findings provide descriptive insights into antigenic differences between clade 1 and clade 2.3.4.4b viruses and support the antigenic relevance of clade 2.3.4.4b CVVs for contemporary H5N1 strains. This study highlights the importance of ongoing antigenic evaluation to inform vaccine strain selection within a One Health framework.

Source: 

Link: https://www.mdpi.com/2076-393X/14/4/301

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A Phase 1/2 Dose-Ranging Safety and Immunogenicity Study of #mRNA-Based Candidate #Pandemic #Influenza #Vaccines in Healthy Adults

 

Abstract

Background

Influenza A viruses pose a persistent pandemic threat. We report safety, reactogenicity, and immunogenicity findings for mRNA-1018 pandemic influenza vaccine candidates from a phase 1/2 study in healthy adults.

Methods

In Part A, participants were randomized to receive 1 of 4 mRNA-1018 candidates at 1 of 3 dose levels across 2 influenza A groups: (1) H5N8/H5-only or (2) H7N9/H7-only. H5N8 and H7N9 candidates were administered at 25, 50, or 100-µg and H5-only and H7-only at 12.5, 25, or 50-µg. Part B participants were randomized to receive 12.5, 25, or 50-µg H5-only-CG. Primary objectives were to evaluate the safety and reactogenicity of vaccine candidates. Secondary objectives included evaluation of humoral immunogenicity through day 205 by hemagglutination inhibition (HAI), neuraminidase inhibition, and microneutralization assays.

Results

Parts A and B comprised 1195 and 304 dosed participants, respectively. Overall, solicited local adverse reactions (ARs) within 7 days of vaccination occurred in 76.8% of participants across vaccine candidates and dose levels, most commonly injection-site pain. Solicited systemic ARs were reported in 62.8% of participants, most frequently fatigue and headache. Solicited ARs were predominantly grade 1–2 in severity, with few grade 3 and no grade 4 events. Post-vaccination immune responses, assessed absolutely, by HAI titers and dynamically, by seroconversion rates, tended to increase with vaccine dose. H5-based candidates induced stronger strain-specific HAI, but with comparable microneutralization titers, versus H7-based candidates.

Conclusions

Vaccine candidates were sufficiently well-tolerated and immunogenic. Further development of mRNA pandemic influenza vaccines is warranted for pandemic preparedness.

Source: 

Link: https://academic.oup.com/cid/advance-article/doi/10.1093/cid/ciag278/8662346

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#Prion shedding is reduced by chronic wasting disease {#CWD} #vaccination

 

Abstract

Chronic wasting disease (CWD) is a strictly fatal and highly contagious prion disease of wild and farmed cervids currently expanding in North America. Prion diseases are caused by conversion of the cellular prion protein to its pathological isoform PrPSc. Vaccination is considered a promising strategy to contain CWD, even though prion diseases do not show classical immune responses. For CWD containment, it is important that vaccines reduce shedding of prions in excreta, a major contributor to transmission. Here, we tested the effect of vaccines on prion shedding in feces and urine by vaccinating and prion infecting knock-in mice that recapitulate CWD pathogenesis as found in cervids. Vaccination reduced or even prevented CWD shedding in feces and urine collected between 30–90% of incubation time to disease. This is the first report showing that prion shedding can be blocked in a prion disease. For CWD specifically it may reduce the environmental prion burden and break the disease transmission cycle.

Source: 

Link: https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1014166

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#Measles - #Bangladesh (WHO, D.O.N., April 23 '26)

 

Situation at a glance

On 4 April 2026, the National International Health Regulations (IHR) Focal Point for Bangladesh notified WHO of a nationwide increase in measles cases, geographically affecting 58 out of 64 districts across all eight divisions in Bangladesh. 

A total of 19 161 suspected measles cases and 2897 laboratory-confirmed measles cases have been reported between 15 March and 14 April 2026, including 166 measles related deaths (CFR 0.9%). 

The majority (79%) of the reported cases are children aged under 5 years. 

A targeted measles-rubella (MR) vaccination campaign started on 5 April, and various outbreak response measures are ongoing including strengthening nationwide surveillance and epidemiological analysis to enhance case detection and reporting. 

Based on currently available information, WHO assesses the risk at the national level as high due to ongoing transmission across multiple divisions, the large number of susceptible children, documented immunity gaps, and the occurrence of suspected measles-related deaths.

Description of the situation

On 4 April 2026, the National IHR Focal Point of Bangladesh notified WHO of a significant increase in measles cases, driven by sustained domestic transmission. 

Since January 2026, Bangladesh has experienced a marked increase in measles cases. 

Geographically, cases have been reported across all eight divisions, in 58 out of 64 districts (91% of districts), indicating widespread transmission nationally.  

Since 15 March 2026 and as of 14 April, a total of 19 161 suspected measles cases and 2973 laboratory-confirmed measles cases have been reported. 

Moreover, 166 suspected measles-related deaths (CFR 0.9%) and 30 confirmed measles-related deaths (CFR= 1.1%) have been recorded. 

A total of 12 318 hospital admissions and 9772 hospital discharges have also been reported. 

The highest cumulative burden of suspected measles cases since 15 March 2026 has been reported in Dhaka (8263 cases), Rajshahi (3747 cases), Chattogram (2514 cases), and Khulna (1568 cases). 

In Dhaka, cases are concentrated in densely populated informal settlements, including Demra, Jatrabari, Kamrangirchar, Korail, Mirpur, and Tejgaon industrial and slum clusters.  (HEOC, DGHS, 15 April 2026).

Children aged under 5 years account for the majority of reported cases (79%), including children aged under 2 years (66%) and infants aged under 9 months (33%). 

A total of 166 suspected deaths have been reported (CFR 1%), mainly among unvaccinated children aged under 2 years.

Epidemiology

Measles is a highly contagious acute viral disease which affects individuals of all ages and remains one of the leading causes of death among young children globally. The mode of transmission is airborne or via droplets from the nose, mouth, or throat of infected persons.

Initial symptoms, which usually appear 10-14 days (range 7-23 days) after infection, include high fever, usually accompanied by a runny nose, bloodshot eyes, cough and tiny white spots inside the mouth. The rash usually appears 10-14 days after exposure and spreads from the head to the trunk to the lower extremities. A person is infectious from four days before up to four days after the appearance of the rash. There is no specific antiviral treatment for measles, and most people recover within 2-3 weeks.

Measles is usually a mild or moderately severe disease. However, measles can lead to complications such as pneumonia, diarrhoea, secondary ear infection, inflammation of the brain (encephalitis), blindness, and death. Postinfectious encephalitis can occur in about one in every 1000 reported cases. About two or three deaths may occur for every 1000 reported cases.

Vaccination with measles containing vaccine is safe and effective, providing protection against measles and its complications for all eligible populations. WHO recommends two doses of Measles Containing Vaccine (MCV) to be provided through the routine immunization schedule. Strong routine immunization systems are therefore critical foundations for achieving and sustaining high levels of population immunity to vaccine preventable diseases such as measles.

WHO further recommends the conduct of Supplementary Immunization Activities (SIAs) or mass immunization campaigns as an effective strategy for delivering vaccination to children who may have been missed by routine services. In protecting vulnerable populations against measles, mass vaccination campaigns can rapidly improve population immunity by reducing the number of susceptible individuals in the population.

Public health response

A nationwide measles-rubella (MR) vaccination campaign was approved by the National Immunization Technical Advisory Group (NITAG) on 30 March 2026, targeting children aged 6–59 months (with expanded coverage for 6–8 months), and started on 5 April in 30 upazilas (sub-districts) of 18 priority districts. A nationwide campaign commenced on 20 April. 

Vitamin A campaign was held throughout the country on 15 March 2025.  During this outbreak response, Vitamin A supplementation is provided to all suspected and confirmed measles cases as an essential component of standard treatment and case management. 

District Rapid Response Teams (RRTs) have been activated, and vaccine procurement fast-tracked by the Ministry of Health. Other outbreak response actions include strengthening routine immunization to prevent further spread of the outbreak, enhancing hospital preparedness, ensuring availability of vitamin A, strengthening isolation capacity, and reinforcing infection prevention and control measures. 

Strengthening nationwide surveillance and epidemiological analysis, is also ongoing including measures to improve case detection and reporting. Trainings are being conducted at health facilities to improve case detection and reporting, and weekly situation reports produced to support evidence-based decision-making. 

National and divisional guidelines have been issued to guide response activities, including vaccination, clinical management, infection prevention and control, patient care pathways, and procurement. 

WHO risk assessment

Measles is a highly contagious viral disease that affects susceptible individuals of all ages and remains one of the leading causes of death among young children globally. Measles can cause serious illness in at-risk groups, including children under 5 years of age, those who are malnourished especially those with vitamin A deficiency and people with weakened immune systems. Measles complications include hearing loss, diarrhoea, pneumonia and blindness. Severe complications of measles include encephalitis, brain damage, and death. 

The current outbreak in Bangladesh is occurring in the context of suboptimal population immunity. A substantial proportion of cases occurred among children who were either unvaccinated or had received only one dose of measles-containing vaccine. In addition, some children were infected before reaching the age of eligibility for vaccination at 9 months. Most cases (91%) occurred among children aged 1 to 14 years, indicating substantial immunity gaps in this age group. 

Before this outbreak, Bangladesh had made substantial progress towards measles elimination. Reported coverage with the first dose of measles-containing vaccine increased considerably between 2000 (89% - WUENIC) and 2016 (118% - WUENIC), while coverage with the second dose also improved between its nationwide introduction in 2012 (22% - WUENIC) and 2024 (121% - WUENIC). During the same period, confirmed measles incidence declined sharply. However, recent declines in MR1 and MR2 coverage due to nationwide stockout of MR vaccine between 2024-2025, combined with routine immunization gaps and the absence of regular nationwide supplementary measles-rubella campaigns since 2020, have increased the number of susceptible children and contributed to the current outbreak. 

The risk at the national level is assessed as high due to ongoing transmission across multiple divisions, the large number of susceptible children, documented immunity gaps, and the occurrence of suspected measles-related deaths. The concentration of cases among unvaccinated and under-vaccinated children including infants too young to be vaccinated, raises concern for continued uninterrupted transmission and severe disease outcomes. 

Overall, the outbreak suggests a reversal from Bangladesh’s previous progress towards measles elimination and highlights increasing vulnerability to sustained transmission. Continued spread is likely unless urgent measures are implemented to strengthen surveillance, rapidly detect and respond to cases, and close immunity gaps through high-quality vaccination activities. 

There are considerable risks of cross-border spread, facilitated by cross-border population movement, with major urban centres such as Dhaka, Chattogram, Sylhet, and Cox’s Bazar being important international travel and transit hubs increasing the likelihood of national and international spread, particularly among unvaccinated or inadequately vaccinated travelers. 

Measles is endemic across the South-East Asia region. The risk is assessed as high at regional level.

Bangladesh shares extensive land borders with India and Myanmar, and population mobility across these borders may facilitate continued transmission. In Myanmar there is a considerable number of unvaccinated/zero dose children. With ongoing conflict and humanitarian crisis, surveillance and response capacities are limited. India, despite achieving high vaccination coverage, has reported a rise in case count over the past six months. Cities with high incidence such as Jashore and Chapainawabganj (an identified hotspot) share busy land crossings with India, thereby increasing the risk of introduction across the border. Despite Bangladesh’s progress towards measles elimination the current outbreak highlights the vulnerability of the population and underscores the fragility of immunization gains.

The risk at the global level is assessed as moderate due to high levels of population mobility, combined with ongoing widespread measles transmission and immunity gaps.

WHO advice

WHO recommends maintaining sustained homogeneous coverage of at least 95% with the first and second doses of the MCV vaccine in all municipalities and strengthening integrated epidemiological surveillance of measles and rubella to achieve timely detection of all suspected cases in public, private, and social security healthcare facilities.  

WHO recommends strengthening epidemiological surveillance in high-traffic border areas to rapidly detect and respond to highly suspected measles cases. Providing a rapid response to imported measles cases to avoid the re-establishment of endemic transmission through the activation of rapid response teams trained for this purpose and by implementing national rapid response protocols when there are imported cases. Once a rapid response team has been activated, continued coordination between the national, sub-national, and local levels must be ensured, with permanent and fluid communication channels between all levels. During outbreaks, it is recommended to establish adequate hospital case management to avoid nosocomial transmission, with appropriate referral of patients to isolation rooms (for any level of care) and avoiding contact with other patients in waiting rooms and/or other hospital rooms.  

WHO recommends vaccination of at-risk populations (without proof of vaccination or immunity against measles and rubella), such as healthcare workers, persons working in tourism and transportation (hotels, airports, border crossings, mass transportation, and others), and international travelers. Implementing a plan to immunize migrant populations in high-traffic border areas, prioritizing those considered at-risk, including both migrants and residents, in these municipalities increases vaccination coverage to increase population immunity.  

In all settings, consideration should be given to providing susceptible contacts with post-exposure prophylaxis (PEP), including a dose of MCV or normal human immunoglobulin (NHIG) (if available) for those at risk and in whom the vaccine is contraindicated. In well-resourced settings, MCV should be provided to susceptible contacts within 3 days. For contacts for whom vaccination is contraindicated or is not possible within 3 days post-exposure, consideration can be given to providing NHIG up to 6 days post-exposure. Infants, pregnant women, and the immunocompromised should be prioritized.  

WHO recommends maintaining a stock of the MR and/or measles, mumps, rubella (MMR) vaccine, and syringes/supplies for control actions of imported cases. Facilitating access to vaccination services according to the national scheme to those from other countries or people from the same country who perform temporary activities in countries with ongoing outbreaks; displaced populations; indigenous populations, or other vulnerable populations.  

WHO does not recommend any restriction on travel and trade based on the information available on the current outbreak.  

Further information

-- World Health Organization. Measles [Internet]. Geneva: World Health Organization; [cited 2026 Apr 6]. Available from: https://www.who.int/health-topics/measles 

-- World Health Organization. Measles fact sheet [Internet]. Geneva: World Health Organization; 2025 Nov 28 [cited 2026 Apr 6]. Available from: https://www.who.int/news-room/fact-sheets/detail/measles  

-- World Health Organization. Immunization dashboard [Internet]. Geneva: World Health Organization; [cited 2026 Apr 6]. Available from: https://immunizationdata.who.int/  

-- World Health Organization. Measles outbreak guide [Internet]. Geneva: World Health Organization; 2022 Aug 31 [cited 2026 Apr 6]. Available from: https://www.who.int/publications/i/item/9789240052079  

-- Directorate General of Health Services (Bangladesh). Press releases [Internet]. Dhaka; [cited 2026 Apr 6]. Available from: https://dghs.gov.bd/pages/press-releases/  

-- Measles vaccines: WHO position paper – April 2017; https://www.who.int/publications/i/item/who-wer9217-205-227

-- Measles: Vaccine Preventable Diseases Surveillance Standards; https://www.who.int/publications/m/item/vaccine-preventable-diseases-surveillance-standards-measles

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Citable reference: World Health Organization (23 April 2026). Disease Outbreak News: Measles in Bangladesh. Available at: https://www.who.int/emergencies/disease-outbreak-news/item/2026-DON598

Source: 

Link: https://www.who.int/emergencies/disease-outbreak-news/item/2026-DON598

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Heterologous Sequential #mRNA #Vaccination of Indian Rhesus #Macaques Elicits Broad Binding and Neutralizing #Antibody Responses Against Diverse #Henipaviruses

 

Abstract

Henipaviruses (HNVs), including Nipah virus (NiV) and Hendra virus (HeV), are highly pathogenic and often lethal zoonotic viruses with broad species tropism and no approved human vaccines. The emergence of genetically divergent HNVs—including Ghana virus (GhV), Langya virus (LayV), and Mojiang virus (MojV)—emphasizes the need for broadly protective countermeasures. Here, we evaluated the antibody (Ab) responses to sequential mRNA vaccines encoding the membrane-bound attachment glycoprotein (gG) from NiV, GhV, and/or LayV in a pilot study with Indian rhesus macaques. Serum binding Ab responses were quantified by ELISA against five soluble gG antigens (NiV, HeV, GhV, LayV, MojV). Functional activity was assessed by neutralization assays using NiV, HeV, and GhV pseudoviruses, and by receptor-blocking ELISA. Sequential vaccination induced high-titer IgG binding against all five HNV gGs with increasing breadth after each dose. Pan-genus regimens elicited moderate neutralizing Ab titers against NiV, HeV, and GhV, whereas the NiV-only regimen elicited potent but narrow neutralization against NiV and HeV. Conversely, the GhV-LayV-GhV regimen elicited strong binding to GhV, LayV, and MojV gG and robust neutralization of GhV pseudovirus, but limited cross-reactivity to NiV and HeV. In this pilot study, we demonstrated that mRNA vaccination can elicit broadly reactive binding and neutralizing Ab responses across phylogenetically distant HNVs. Additionally, we show GhV pseudovirus neutralization for the first time. Collectively, these data provide a foundation for the development of next-generation pan-genus HNV vaccines capable of mitigating future HNV outbreaks.

Source: 

Link: https://www.mdpi.com/1999-4915/18/5/487

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Dual-route #H5N1 #vaccination induces systemic and mucosal #immunity in murine and bovine #models

 

Abstract

Highly pathogenic H5N1 avian influenza (clade 2.3.4.4b) has spread widely among dairy cattle herds since early 2024, causing major economic losses. This zoonotic event emphasizes the urgent need for H5 vaccines eliciting strong, durable, cross-reactive immune responses in cows. To address this, we immunized mice and cattle with a centralized consensus H5 vaccine, localizing near the central node of the human H5 phylogenetic tree. The vaccine was delivered using serotype-switched adenoviral vectors in a prime–boost regimen, combined with intramuscular and intranasal coadministration to target systemic and mucosal immunity and elicit strong humoral and cellular immune responses. This approach strategically integrates multiple innovative features: centralized consensus immunogens, mucosal targeting, and vector serotype switching aimed at maximizing immune protection against H5N1 viruses. Our results show that vaccination elicits strong humoral and cellular immunity in both mice and calves. In challenge experiments, vaccinated mice were fully protected against lethal infection with divergent H5N1 strains, including A/bovine/Ohio/B24OSU-439/2024. Vaccine-induced immunity was consistent across species, supporting the translatability of the mouse model findings to cattle. Overall, our findings represent a promising approach for immunizing key livestock, including cattle, against highly pathogenic avian influenza H5N1, mitigating agricultural losses, and reducing the risk of zoonotic transmission.

Source: 

Link: https://www.nature.com/articles/s41541-026-01460-6

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Cross - #protection against highly pathogenic avian #influenza #H5N1 virus from seasonal influenza #vaccines: a systematic review and meta-analysis of #ferret studies

 

ABSTRACT

The recent surge in spillover events of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b to humans and mammals in North America has raised urgent pandemic concerns. Human H5N1 vaccines are unavailable in most countries. We synthesized data from ferret challenge trials to evaluate whether widely available seasonal influenza vaccines confer cross-protection against lethal H5N1 infection. We systematically searched PubMed, Embase, and Web of Science for ferret studies of lethal H5N1 challenge published up to 5 July 2025 (PROSPERO #CRD42024520346). Random-effects meta-analyses were conducted to compare vaccine efficacy (VE) of seasonal influenza vaccines and H5N1 vaccines against H5N1-related mortality. Seroprotection was defined as a neutralizing antibody titre of ≥1:40. We identified 35 studies (157 trials). Seasonal influenza vaccines without N1 did not confer significant cross-protection (five trials; VE 14.8%, 95% CI –3.6 to 30.0). In contrast, VE was 73% for N1-containing seasonal influenza vaccines (19 trials; 95% CI 54–84) and 77% for H5N1 vaccines overall (133 trials; 95% CI 72–82) (p = 0.52). The VE of N1-containing seasonal influenza vaccines was modestly lower than that of H5N1 vaccines with seroprotection (88%; 66 trials; 95% CI 84–91; p = 0.009), but comparable to H5N1 vaccines that did not achieve seroprotection (63%; 67 trials; 95% CI 52–71; p = 0.29). The VE of seasonal influenza vaccines against H5N1 was robust across sensitivity analyses, with no evidence of publication bias (p = 0.99). Seasonal influenza vaccines significantly reduce H5N1-associated mortality in ferret trials, suggesting the cross-protection potential of currently available vaccines. Human studies are warranted.

Source: 

Link: https://www.tandfonline.com/doi/full/10.1080/22221751.2026.2654278

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#SARS-CoV-2 #vaccination and #infection elicit cross-neutralizing responses against clade 3 and 4 #sarbecoviruses

 

Abstract

Two sarbecoviruses, SARS-CoV-1 and SARS-CoV-2 that engage ACE2 through their receptor-binding domains, have caused major human outbreaks. The pandemic potential of sarbecoviruses has prompted the discovery and classification of bat and other zoonotic sarbecoviruses that are also able to use human ACE2 or ACE2 ortholog receptors for infection. However, the current human immunological landscape reactive to these SARS-CoV-2-related viruses is not well profiled. Using a panel of pseudotyped lentiviruses expressing only spike proteins, we assess serum neutralization activity against clade 3 and 4 (also designated as clade 1c) receptor binding domain classified sarbecoviruses in a cohort who received a primary series of COVID-19 mRNA vaccines as well as individuals before and after infection with BA.5 or XBB.1.5 variants. Detectable neutralizing responses against clade 3 and 4 sarbecoviruses are observed in both vaccinees and convalescents and are comparable in magnitude to titers against SARS-CoV-2 variants. Infection with XBB.1.5 increases neutralization titers against SARS-CoV-2 variants as well as against clade 3 and 4 sarbecoviruses. Collectively, our findings suggest that the current immunologic landscape of vaccination and infection may confer some level of immunity against a variety of clade 3 and 4 sarbecoviruses, which should inform future pandemic response and pan-sarbecovirus countermeasure efforts.

Source: 

Link: https://www.nature.com/articles/s41467-026-71662-y

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#Vaccine-Elicited #Antibody Responses to #Influenza #H3N2 Subclade K

 

{Summary}

Influenza A(H3N2) subclade K (J.2.4.1) is a genetic branch of H3N2 with 11 mutations in hemagglutinin compared with the A/H3N2/Croatia/10136RV/2023 (H3N2 CR/23) vaccine strain, of which 8 mutations are on the hemagglutinin head surface (...) (...). As of February 2026, influenza A viruses currently represent approximately 96.3% of circulating influenza strains in the US, with H3N2 accounting for 88.4% of influenza isolates and subclade K comprising 91.5% of H3N2 isolates. The rapid expansion of H3N2 subclade K represents a major public health concern. This study reports antibody responses to H3N2 subclade K and other influenza strains before and after influenza vaccination.

(...)

Source: 

Link: https://jamanetwork.com/journals/jama/article-abstract/2846268

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#Preclinical evaluation of an #mRNA #vaccine developed from the first #human isolate of #bovine #H5N1

 

Highlights

• SM102 and DB-Y ionizable lipids deliver H5 mRNA vaccine with high efficiency and safety

• Vaccine-induced antibody and T cell response protect mice from H5N1 challenge

• Pre-existing H1 immunity does not diminish H5-specific immunogenicity

• Vaccine fully protects chicken against clade 2.3.4.4b/h H5 virus challenge

Summary

Given the global threat posed by H5N1 clade 2.3.4.4b avian influenza, rapid development of effective vaccines is imperative. We design an mRNA vaccine encoding hemagglutinin (HA) from A/Texas/37/2024, the first bovine-to-human strain. In murine models, both wild-type and cleavage-site-modified HA vaccines elicit robust and durable humoral immunity, along with a balanced Th1/Th2 response, conferring complete protection against lethal homologous viral challenge. The vaccine, along with the World Health Organization (WHO)-recommended candidate (A/Astrakhan/3212/2020), elicits cross-clade binding antibody responses and demonstrates improvement against specific clades at a 1 μg dose. Pre-existing H1 immunity does not diminish H5-specific immunogenicity. In avian species, the vaccine also provides full protection against lethal clades (2.3.4.4b and 2.3.4.4h). Formulated with another ionizable lipid, the vaccine elicits responses comparable to benchmark lipid nanoparticles (LNPs) and shows a favorable safety profile in rats. This work establishes a rapidly adaptable mRNA-LNP vaccine prototype for pandemic preparedness against evolving avian influenza threats.

Source: 

Link: https://www.cell.com/cell-reports-medicine/fulltext/S2666-3791(26)00119-9?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS2666379126001199%3Fshowall%3Dtrue

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MF59-adjuvanted A/Astrakhan #influenza #vaccine induces cross-neutralizing #H5N1 #antibodies in #ferrets against circulating clade 2.3.4.4b viruses

 

Abstract

The continued global spread of highly pathogenic avian influenza A(H5N1) viruses, particularly clade 2.3.4.4b, has increased zoonotic spillover risk and underscored the urgency of pandemic preparedness. Human vaccination is a key strategy for mitigating severe disease and limiting transmission, especially in a setting where avian influenza viruses pose a zoonotic threat. We evaluated the immunogenicity of the MF59-adjuvanted, egg-derived A/Astrakhan/3212/2020 (H5N8) influenza vaccine (CBER-RG8A) in ferrets. To assess cross-reactivity, we generated pseudoviruses bearing HA and NA from circulating A(H5N1) 2.3.4.4b viruses, including North American (B1.13 and D1.1) and Eurasian (DI.2) genotypes. Immunogenicity was assessed using hemagglutination inhibition and microneutralization assays. A single dose elicited robust neutralizing titers (GMT ≥ 160), while a second dose increased titers by ≥3.3-fold. Cross-reactivity was maintained across most strains; however, responses were reduced up to 8-fold against strains harboring the A156T HA mutation, which may introduce a glycosylation site at antigenic site B. Limited responses were detected against divergent clades, with modest titers against clade 2.3.2.1a. These findings suggest broad protection induced by the CSL Seqirus pandemic vaccine against contemporary clade 2.3.4.4b A(H5N1) viruses and underscore the value of ferret immunogenicity data in informing strain selection and regulatory preparedness when human clinical data are unavailable.

Source: 

Link: https://www.nature.com/articles/s41541-026-01438-4

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Current #status of #intranasal and inhaled #COVID19 #vaccines

 

Abstract

The COVID-19 pandemic has accelerated the development of intranasal and inhaled COVID-19. vaccines. Four vector-based and one adjuvanted protein-based vaccines have been licenced. They have been shown to be safe. However, their ability to induce strong protective mucosal immunity in humans remains to be improved. Diversifying intranasal vaccine platforms, improving the delivery of vaccine components and determining mucosal correlates of protection could help in optimizing intranasal COVID-19 vaccine efficacy.

Source: 

Link: https://www.nature.com/articles/s41541-026-01432-w

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Broad #protection against #Influenza A Viruses via an adjuvant-free #mucosal microparticle #vaccine with conserved CD8/CD4 bispecific peptides

 

Abstract

Influenza A viruses (IAVs) cause substantial global morbidity and mortality and are responsible for most known viral pandemics. Their rapid antigenic evolution enables escape from natural and vaccine-induced immunity, requiring annual vaccine reformulation, which offers limited breadth and variable effectiveness. Although a universal influenza vaccine remains a critical objective, most strategies have focused on conserved viral glycoproteins to elicit broadly neutralizing antibodies, with comparatively fewer efforts targeting conserved T cell antigens to achieve cross-subtype protection. Current T cell-based approaches often rely on individual CD8+ epitopes, which are limited by peptide instability, delivery constraints, and dependence on adjuvants. Here, we demonstrate a T cell-focused vaccine strategy that uses evolutionary consensus of IAV M1 and NP from the H1N1 and H3N2 subtypes to predict, map, and screen conserved regions enriched with multiple CD8+ and CD4+ epitopes. We selected the top-performing peptides from immunogenicity screening. We encapsulated them in polylactic-co-glycolic acid microparticles (PLGA-MPs) engineered for selective uptake by APCs and pH-dependent sustained release. Intranasal delivery of this vaccine formulation targeted the primary site of infection and induced robust mucosal immunity without the need for conventional adjuvants. Both human and murine influenza-experienced T cells mounted potent recall responses to the vaccine. In mice, immunization elicited strong CD8+ and CD4+ T cell responses and conferred broad protection against homologous H1N1 and H3N2 as well as heterologous H5N1 IAV subtypes. These findings collectively establish a mucosal, T cell-based vaccine platform that is adjuvant-free and capable of providing broad protection against IAV and other viruses with pandemic potential.

Competing Interest Statement

The authors have declared no competing interest.

Funder Information Declared

DBT-ENDFLU, BT/IN/EU-INF/15/RV/19-20

Source: 

Link: https://www.biorxiv.org/content/10.64898/2026.03.29.715080v1

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