Inactivated Zoonotic Influenza A(H5N8) Vaccine Induces Humoral and Cell-mediated Immune Responses Against Highly Pathogenic Avian Influenza Clade 2.3.4.4b A(H5N1) Viruses

Inactivated Zoonotic Influenza A(H5N8) Vaccine Induces Humoral and Cell-mediated Immune Responses Against Highly Pathogenic Avian Influenza Clade 2.3.4.4b A(H5N1) Viruses | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Inactivated Zoonotic Influenza A(H5N8) Vaccine Induces Humoral and Cell-mediated Immune Responses Against Highly Pathogenic Avian Influenza Clade 2.3.4.4b A(H5N1) Viruses Oona Liedes, Arttu Reinholm, Nina Ekström, Anu Haveri, Anna Solastie, and 19 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6804016/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 05 Dec, 2025 Read the published version in Nature Microbiology → Version 1 posted You are reading this latest preprint version Abstract In 2023, Finland faced an outbreak of highly pathogenic clade 2.3.4.4b A(H5N1) avian influenza, spreading from wild birds to fur farms. Vaccinations of at-risk individuals began in June 2024 using the MF59-adjuvanted inactivated A(H5N8) vaccine (Seqirus; A/Astrakhan/3212/2020, clade 2.3.4.4b). We assessed virus-specific antibody (n=39) and T-cell (n=18) responses. Vaccination elicited functional antibodies against the vaccine virus and two heterologous clade 2.3.4.4b strains associated with outbreaks on Finnish fur farms and dairy cattle in the U.S. Among previously unvaccinated individuals, seroprotection rates against the vaccine virus were 83% (95% CI 70–97%) by microneutralization assay (titer ≥20) and 97% (90–100%) by hemagglutination inhibition assay (titer ≥40). In all those previously vaccinated against avian influenza, a single dose induced seroprotection. A(H5N8)-specific memory CD4+ T-cell responses were detectable, with ~5-fold increase in IFN-γ secretion after two doses. These results demonstrate that the vaccine likely provides cross-protection against circulating H5 clade 2.3.4.4b viruses. Biological sciences/Immunology/Vaccines Biological sciences/Microbiology/Virology/Influenza virus Full Text Additional Declarations Yes there is potential Competing Interest. Alessandro Sette is a consultant for Alcimed, Arcturus, Darwin Health, Desna Therapeutics, EmerVax, Gilead Sciences, Guggenheim Securities, Link University and RiverVest Venture Partners. La Jolla Institute for Immunology (LJI) has filed for patent protection for various aspects of T cell epitope and vaccine design work. Ritva K. Syrjänen has acted or acts as a sub-investigator in a COVID-19 study sponsored by Pfizer, pneumococcal carriage study sponsored by Merck Sharp & Dohme and influenza, pertussis and meningitis studies sponsored by Sanofi Pasteur, not related to this work. Her current affiliation Finnish Vaccine Research (FVR) conducts clinical trials and studies sponsored by almost all vaccine providers, not related to this work. Hanna Nohynek is member of the National Immunization Technical Advisory Group, THL, Finland and the chair of the WHO Strategic Advisory Group of Experts. Merit Melin is a member of the National Immunization Technical Advisory Group, THL, Finland. Supplementary Files Extendeddata.pdf Extended data Figs and Tables Cite Share Download PDF Status: Published Journal Publication published 05 Dec, 2025 Read the published version in Nature Microbiology → Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6804016","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":465454152,"identity":"2a23110f-b9cf-4335-a22c-e875a4a653dc","order_by":0,"name":"Oona 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Guggenheim Securities, Link University and RiverVest Venture Partners. La Jolla Institute for Immunology (LJI) has filed for patent protection for various aspects of T cell epitope and vaccine design work. Ritva K. Syrjänen has acted or acts as a sub-investigator in a COVID-19 study sponsored by Pfizer, pneumococcal carriage study sponsored by Merck Sharp \u0026 Dohme and influenza, pertussis and meningitis studies sponsored by Sanofi Pasteur, not related to this work. Her current affiliation Finnish Vaccine Research (FVR) conducts clinical trials and studies sponsored by almost all vaccine providers, not related to this work. Hanna Nohynek is member of the National Immunization Technical Advisory Group, THL, Finland and the chair of the WHO Strategic Advisory Group of Experts. 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Vaccinations of at-risk individuals began in June 2024 using the MF59-adjuvanted inactivated A(H5N8) vaccine (Seqirus; A/Astrakhan/3212/2020, clade 2.3.4.4b). We assessed virus-specific antibody (n=39) and T-cell (n=18) responses. Vaccination elicited functional antibodies against the vaccine virus and two heterologous clade 2.3.4.4b strains associated with outbreaks on Finnish fur farms and dairy cattle in the U.S. Among previously unvaccinated individuals, seroprotection rates against the vaccine virus were 83% (95% CI 70–97%) by microneutralization assay (titer ≥20) and 97% (90–100%) by hemagglutination inhibition assay (titer ≥40). In all those previously vaccinated against avian influenza, a single dose induced seroprotection. A(H5N8)-specific memory CD4+ T-cell responses were detectable, with ~5-fold increase in IFN-γ secretion after two doses. 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