{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,7]],"date-time":"2026-09-07T00:58:21Z","timestamp":1788742701879,"version":"build-2803163510"},"reference-count":40,"publisher":"Wiley","issue":"3","license":[{"start":{"date-parts":[[2026,3,12]],"date-time":"2026-03-12T00:00:00Z","timestamp":1773273600000},"content-version":"vor","delay-in-days":11,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"},{"start":{"date-parts":[[2026,3,1]],"date-time":"2026-03-01T00:00:00Z","timestamp":1772323200000},"content-version":"tdm","delay-in-days":0,"URL":"http:\/\/doi.wiley.com\/10.1002\/tdm_license_1.1"}],"content-domain":{"domain":["onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Influenza Resp Viruses"],"published-print":{"date-parts":[[2026,3]]},"abstract":"<jats:title>ABSTRACT<\/jats:title>\n                  <jats:sec>\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>In the 2024\u20132025 season, influenza activity returned to pre\u2010COVID\u201019 pandemic levels, with A(H1N1)pdm09 as the predominant subtype. Reassessment vaccine effectiveness (VE) in hospitalized patients is critical to inform potential adjustments to vaccination policy.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>Using a test\u2010negative design, we evaluated the VE of the seasonal influenza vaccine during the 2024\u20132025 season against A(H1N1)pdm09\u2010associated hospitalizations with severe acute respiratory infections (SARI) in Beijing, China, from December 9, 2024 to February 9, 2025. VE was estimated by comparing the odds of influenza vaccination between case\u2010patients (those testing positive for A(H1N1)pdm09) and controls (influenza test\u2010negative patients), applying inverse\u2010propensity\u2010to\u2010be\u2010vaccinated weights.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>The analysis included 1608 hospitalized SARI patients (17.4% tested positive for A(H1N1)pdm09; 13.8% were vaccinated overall). The adjusted VE against A(H1N1)pdm09\u2010associated hospitalizations was 18.8% (95% CI: 0.9% to 33.6%) overall. Specifically, the VE was 45.4% (95% CI: 10.0% to 67.1%) in children aged 0.5\u201317\u2009years, 43.8% (95% CI: \u221220.8% to 76.1%) in adults aged 18\u201359\u2009years, and 8.6% (95% CI: \u221215.8% to 27.9%) in older adults\u2009\u2265\u200960\u2009years. Among individuals with chronic conditions, the VE was 18.5% (95% CI: \u22122.3% to 35.2%) and was higher among those with chronic respiratory conditions (40.6%, 95% CI: \u22121.7% to 65.7%).<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>During the 2024\u20132025 season in Beijing, the overall VE against A(H1N1)pdm09\u2010associated SARI hospitalizations was suboptimal. However, moderate VE was observed among children and younger adults, while limited effectiveness was seen in the elderly. Optimizing influenza vaccination strategies, including the introduction of high\u2010dose or adjuvanted vaccines to enhance immune response in older adults, is crucial to alleviate influenza\u2010associated hospitalizations.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1111\/irv.70248","type":"journal-article","created":{"date-parts":[[2026,3,12]],"date-time":"2026-03-12T07:20:47Z","timestamp":1773300047000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Influenza Vaccine Effectiveness Against Influenza A(H1N1)pdm09\u2010Associated Hospitalizations With SARI in Beijing, China, in the 2024\u20132025 Season"],"prefix":"10.1111","volume":"20","author":[{"given":"Chunna","family":"Ma","sequence":"first","affiliation":[{"name":"Beijing Research Center for Respiratory Infectious Diseases  Beijing China"},{"name":"Beijing Key Laboratory of Surveillance, Early Warning and Pathogen Research on Emerging Infectious 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China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jiaxin","family":"Ma","sequence":"additional","affiliation":[{"name":"Beijing Research Center for Respiratory Infectious Diseases  Beijing China"},{"name":"Beijing Key Laboratory of Surveillance, Early Warning and Pathogen Research on Emerging Infectious Diseases Beijing Center for Disease Prevention and Control  Beijing China"},{"name":"Institute for Infectious Disease and Endemic Disease Control Beijing Center for Disease Prevention and Control  Beijing China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yingying","family":"Wang","sequence":"additional","affiliation":[{"name":"Beijing Research Center for Respiratory Infectious Diseases  Beijing China"},{"name":"Beijing Key Laboratory of Surveillance, Early Warning and Pathogen Research on Emerging Infectious Diseases Beijing Center for Disease Prevention and Control  Beijing China"},{"name":"Institute for Infectious Disease and Endemic Disease 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