{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,4]],"date-time":"2026-03-04T09:08:02Z","timestamp":1772615282577,"version":"3.50.1"},"reference-count":31,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2026,2,26]],"date-time":"2026-02-26T00:00:00Z","timestamp":1772064000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100000289","name":"Cancer Research UK","doi-asserted-by":"publisher","award":["CC1114"],"award-info":[{"award-number":["CC1114"]}],"id":[{"id":"10.13039\/501100000289","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100000265","name":"UK Medical Research Council","doi-asserted-by":"publisher","award":["CC1114"],"award-info":[{"award-number":["CC1114"]}],"id":[{"id":"10.13039\/501100000265","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100010269","name":"Wellcome Trust","doi-asserted-by":"publisher","award":["CC1114"],"award-info":[{"award-number":["CC1114"]}],"id":[{"id":"10.13039\/100010269","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Vaccines"],"abstract":"<jats:p>Background\/Objectives: Influenza A viruses cause seasonal epidemics of respiratory infections in humans, the severity of which can be mitigated by influenza vaccine use. Influenza A viruses circulating in pigs continue to pose a pandemic threat, as evidenced by the influenza virus that caused the 2009 pandemic, which originated in pigs. To understand the relative risk of emergence of influenza A viruses from pigs and to assess the potential role of the seasonal influenza vaccine in mitigating this risk, we evaluate the potential cross-protection afforded by the seasonal influenza vaccine against different clades of recently circulating swine influenza A viruses. Methods: The presence of cross-reactive antibodies in pre- and post-vaccination human serum samples was measured in haemagglutination and microneutralisation assays. Representative H1 swine influenza A viruses from different genetic lineages were tested against sera collected after administration of the seasonal influenza vaccine in healthy adult volunteers over a 6-year time-period. Results: Although a clade-dependent boosting of post-vaccination antibody titres was observed, protective titres often failed to be reached. There was heterogeneity in recognition by sera for the contemporary swine influenza A viruses, with the 1C.2.1 clade virus being well recognised in both assays, whilst very low pre- and post-vaccination antibody titres were observed against the 1A.3.3.2 clade (which emerged in pigs following the reverse zoonotic introduction from humans of the A\/H1N1 pdm09 virus) by both assays. Conclusions: Seasonal influenza vaccines produce cross-reactive antibodies against some clades of influenza A viruses circulating in pigs, but not all. Depending on the lineage and clade of the virus, the seasonal influenza vaccine might have utility in the event of a swine variant outbreak in humans, whilst a specific vaccine against the outbreak strain is developed.<\/jats:p>","DOI":"10.3390\/vaccines14030211","type":"journal-article","created":{"date-parts":[[2026,2,26]],"date-time":"2026-02-26T14:51:29Z","timestamp":1772117489000},"page":"211","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Investigation of Potential Cross-Protection Conferred by the Seasonal Influenza Vaccine Against Swine Influenza A Viruses of Pandemic Potential"],"prefix":"10.3390","volume":"14","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-8180-2798","authenticated-orcid":false,"given":"Alice","family":"Lilley","sequence":"first","affiliation":[{"name":"The Worldwide Influenza Centre, The Francis Crick Institute, London NW1 1AT, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8808-4680","authenticated-orcid":false,"given":"Chiara","family":"Chiapponi","sequence":"additional","affiliation":[{"name":"WOAH Reference Laboratory for Swine in Influenza, Istituto Zooprofilattico Sperimentale Della Lombardia e dell\u2019Emilia Romagna, 25124 Brescia, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1134-9764","authenticated-orcid":false,"given":"Alice","family":"Prosperi","sequence":"additional","affiliation":[{"name":"WOAH Reference Laboratory for Swine in Influenza, Istituto Zooprofilattico Sperimentale Della Lombardia e dell\u2019Emilia Romagna, 25124 Brescia, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8497-9708","authenticated-orcid":false,"given":"Ana","family":"Moreno","sequence":"additional","affiliation":[{"name":"WOAH Reference Laboratory for Swine in Influenza, Istituto Zooprofilattico Sperimentale Della Lombardia e dell\u2019Emilia Romagna, 25124 Brescia, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3497-1601","authenticated-orcid":false,"given":"Laura","family":"Soliani","sequence":"additional","affiliation":[{"name":"WOAH Reference Laboratory for Swine in Influenza, Istituto Zooprofilattico Sperimentale Della Lombardia e dell\u2019Emilia Romagna, 25124 Brescia, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Nicola","family":"Lewis","sequence":"additional","affiliation":[{"name":"The Worldwide Influenza Centre, The Francis Crick Institute, London NW1 1AT, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ruth","family":"Harvey","sequence":"additional","affiliation":[{"name":"The Worldwide Influenza Centre, The Francis Crick Institute, London NW1 1AT, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2026,2,26]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"4638","DOI":"10.1002\/jmv.26990","article-title":"A brief review of influenza virus infection","volume":"93","author":"Javanian","year":"2021","journal-title":"J. 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