{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,20]],"date-time":"2026-05-20T10:09:56Z","timestamp":1779271796832,"version":"3.51.4"},"reference-count":28,"publisher":"MDPI AG","issue":"5","license":[{"start":{"date-parts":[[2026,5,20]],"date-time":"2026-05-20T00:00:00Z","timestamp":1779235200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Capital\u2019s Funds for Health Improvement and Research","award":["2026-1G-3012"],"award-info":[{"award-number":["2026-1G-3012"]}]},{"name":"Beijing Research Center for Respiratory Infectious Diseases","award":["BJRID2026-001"],"award-info":[{"award-number":["BJRID2026-001"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Vaccines"],"abstract":"<jats:p>Background: Data on influenza vaccine effectiveness (VE) against hospitalized severe acute respiratory infection (SARI), particularly in Asia, remain limited for the 2025\/26 Northern Hemisphere influenza season. This study aimed to evaluate real-world VE against A(H3N2)-associated SARI hospitalization and provide timely, locally relevant evidence to inform seasonal influenza vaccination policy. Methods: A test-negative design was used to estimate VE against influenza A(H3N2)-associated SARI hospitalization in Beijing, China, from 10 November 2025 to 18 January 2026. VE was estimated by comparing the odds of influenza vaccination between case-patients (those who tested positive for A(H3N2)) with controls (those who tested negative for influenza). Results: Among 1883 enrolled SARI inpatients, 220 (11.7%) tested positive for influenza A(H3N2). Overall vaccination coverage was 11.4%, with the highest coverage observed among children aged 5\u201317 years (29.6%). Influenza positivity was higher among rural residents, patients with pneumonia or hypoxemia, and those with symptom onset in November. The adjusted overall VE was 7.5% (95% CI: \u221245.8% to 43.3%). Moderate VE was observed among children aged 5\u201317 years (45.4%, 95% CI: \u221233.6% to 79.5%), although the confidence interval included zero and the estimate was not statistically significant. Negative VE estimates were observed among younger children and older adults. Among patients with underlying respiratory conditions, VE was 75.4% (95% CI: \u221227.4% to 98.7%), although this estimate was also not statistically significant. Conclusions: During the 2025\/26 influenza season in Beijing, VE against A(H3N2)-associated SARI hospitalization was suboptimal. Moderate protection was observed among children aged 5\u201317 years, the group with the highest vaccination coverage, but the estimate was not statistically significant. The low overall VE may be attributable to antigenic mismatch between vaccine and circulating strains, as well as low population-level vaccination coverage. These findings highlight the need to improve vaccine formulations and increase vaccination coverage, particularly among adults and older populations.<\/jats:p>","DOI":"10.3390\/vaccines14050457","type":"journal-article","created":{"date-parts":[[2026,5,20]],"date-time":"2026-05-20T09:12:41Z","timestamp":1779268361000},"page":"457","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Vaccine Effectiveness Estimates Against Influenza A(H3N2)-Associated Hospitalized Severe Acute Respiratory Infections in Beijing, China, 2025\/26 Influenza Season"],"prefix":"10.3390","volume":"14","author":[{"ORCID":"https:\/\/orcid.org\/0009-0007-0690-056X","authenticated-orcid":false,"given":"Chunna","family":"Ma","sequence":"first","affiliation":[{"name":"Beijing Research Center for Respiratory Infectious Diseases, Beijing 100013, China"},{"name":"Beijing Key Laboratory of Surveillance, Early Warning and Pathogen Research on Emerging Infectious Diseases, Beijing Center for Disease Prevention and Control, Beijing 100013, China"},{"name":"Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control, Beijing 100013, China"},{"name":"School of Public Health, Capital Medical University, Beijing 100069, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6249-0426","authenticated-orcid":false,"given":"Jiaojiao","family":"Zhang","sequence":"additional","affiliation":[{"name":"Beijing Research Center for Respiratory Infectious Diseases, Beijing 100013, China"},{"name":"Beijing Key Laboratory of Surveillance, Early Warning and Pathogen Research on Emerging Infectious Diseases, Beijing Center for Disease Prevention and Control, Beijing 100013, China"},{"name":"Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control, Beijing 100013, China"},{"name":"School of Public Health, Capital Medical University, Beijing 100069, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jiaxin","family":"Ma","sequence":"additional","affiliation":[{"name":"Beijing Research Center for Respiratory Infectious Diseases, Beijing 100013, China"},{"name":"Beijing Key Laboratory of Surveillance, Early Warning and Pathogen Research on Emerging Infectious Diseases, Beijing Center for Disease Prevention and Control, Beijing 100013, China"},{"name":"Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control, Beijing 100013, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Wei","family":"Duan","sequence":"additional","affiliation":[{"name":"Beijing Research Center for Respiratory Infectious Diseases, Beijing 100013, China"},{"name":"Beijing Key Laboratory of Surveillance, Early Warning and Pathogen Research on Emerging Infectious Diseases, Beijing Center for Disease Prevention and Control, Beijing 100013, China"},{"name":"Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control, Beijing 100013, China"},{"name":"School of Public Health, Capital Medical University, Beijing 100069, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yingying","family":"Wang","sequence":"additional","affiliation":[{"name":"Beijing Research Center for Respiratory Infectious Diseases, Beijing 100013, China"},{"name":"Beijing Key Laboratory of Surveillance, Early Warning and Pathogen Research on Emerging Infectious Diseases, Beijing Center for Disease Prevention and Control, Beijing 100013, China"},{"name":"Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control, Beijing 100013, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Xiaodi","family":"Hu","sequence":"additional","affiliation":[{"name":"Beijing Research Center for Respiratory Infectious Diseases, Beijing 100013, China"},{"name":"Beijing Key Laboratory of Surveillance, Early Warning and Pathogen Research on Emerging Infectious Diseases, Beijing Center for Disease Prevention and Control, Beijing 100013, China"},{"name":"Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control, Beijing 100013, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jia","family":"Li","sequence":"additional","affiliation":[{"name":"Beijing Research Center for Respiratory Infectious Diseases, Beijing 100013, China"},{"name":"Beijing Key Laboratory of Surveillance, Early Warning and Pathogen Research on Emerging Infectious Diseases, Beijing Center for Disease Prevention and Control, Beijing 100013, China"},{"name":"Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control, Beijing 100013, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Lu","family":"Zhang","sequence":"additional","affiliation":[{"name":"Beijing Research Center for Respiratory Infectious Diseases, Beijing 100013, China"},{"name":"Beijing Key Laboratory of Surveillance, Early Warning and Pathogen Research on Emerging Infectious Diseases, Beijing Center for Disease Prevention and Control, Beijing 100013, China"},{"name":"Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control, Beijing 100013, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yuanzhi","family":"Di","sequence":"additional","affiliation":[{"name":"Beijing Research Center for Respiratory Infectious Diseases, Beijing 100013, China"},{"name":"Beijing Key Laboratory of Surveillance, Early Warning and Pathogen Research on Emerging Infectious Diseases, Beijing Center for Disease Prevention and Control, Beijing 100013, China"},{"name":"Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control, Beijing 100013, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Shuning","family":"Yan","sequence":"additional","affiliation":[{"name":"Beijing Research Center for Respiratory Infectious Diseases, Beijing 100013, China"},{"name":"Beijing Key Laboratory of Surveillance, Early Warning and Pathogen Research on Emerging Infectious Diseases, Beijing Center for Disease Prevention and Control, Beijing 100013, China"},{"name":"Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control, Beijing 100013, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Peng","family":"Yang","sequence":"additional","affiliation":[{"name":"Beijing Research Center for Respiratory Infectious Diseases, Beijing 100013, China"},{"name":"Beijing Key Laboratory of Surveillance, Early Warning and Pathogen Research on Emerging Infectious Diseases, Beijing Center for Disease Prevention and Control, Beijing 100013, China"},{"name":"Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control, Beijing 100013, China"},{"name":"School of Public Health, Capital Medical University, Beijing 100069, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Quanyi","family":"Wang","sequence":"additional","affiliation":[{"name":"Beijing Research Center for Respiratory Infectious Diseases, Beijing 100013, China"},{"name":"Beijing Key Laboratory of Surveillance, Early Warning and Pathogen Research on Emerging Infectious Diseases, Beijing Center for Disease Prevention and Control, Beijing 100013, China"},{"name":"Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control, Beijing 100013, China"},{"name":"School of Public Health, Capital Medical University, Beijing 100069, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ying","family":"Shen","sequence":"additional","affiliation":[{"name":"Beijing Research Center for Respiratory Infectious Diseases, Beijing 100013, China"},{"name":"Beijing Key Laboratory of Surveillance, Early Warning and Pathogen Research on Emerging Infectious Diseases, Beijing Center for Disease Prevention and Control, Beijing 100013, China"},{"name":"Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control, Beijing 100013, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Daitao","family":"Zhang","sequence":"additional","affiliation":[{"name":"Beijing Research Center for Respiratory Infectious Diseases, Beijing 100013, China"},{"name":"Beijing Key Laboratory of Surveillance, Early Warning and Pathogen Research on Emerging Infectious Diseases, Beijing Center for Disease Prevention and Control, Beijing 100013, China"},{"name":"Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control, Beijing 100013, China"},{"name":"School of Public Health, Capital Medical University, Beijing 100069, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2026,5,20]]},"reference":[{"key":"ref_1","unstructured":"U.S. Centers for Diseasecontrol and Prevention (2026, March 09). Weekly US Influenza Surveillance Report: Key Updates for Week 8, Ending 28 February 2026, Available online: https:\/\/www.cdc.gov\/fluview\/surveillance\/2026-week-08.html."},{"key":"ref_2","unstructured":"European Centre for Disease Prevention and Control (2026, January 29). Early Estimates of Seasonal Influenza Vaccine Effectiveness Against Influenza Requiring Medical Attention at Primary Care Level in Europe, Week 41\u201349. 2025. Available online: https:\/\/www.ecdc.europa.eu\/en\/news-events\/early-estimates-seasonal-influenza-vaccine-effectiveness-against-influenza-requiring."},{"key":"ref_3","unstructured":"European Centre for Disease Prevention and Control (2026, March 09). Communicable Disease Threats Report, Week 9, 21\u201327 February 2026. Available online: https:\/\/www.ecdc.europa.eu\/sites\/default\/files\/documents\/Communicable-disease-threats-report-week-9-2026_4.pdf."},{"key":"ref_4","unstructured":"European Centre for Disease Prevention and Control (2026, March 09). Assessing the Risk of Influenza for the EU\/EEA in the Context of Increasing Circulation of A(H3N2)subclade K. Available online: https:\/\/www.ecdc.europa.eu\/en\/publications-data\/threat-assessment-brief-assessing-risk-influenza-november-2025."},{"key":"ref_5","unstructured":"Chinese National Influenza Center (2026, March 09). Chinese Weekly Influenza Surveillance Report, 23 February to 1 March 2026 (Week 9). Available online: https:\/\/ivdc.chinacdc.cn\/cnic\/en\/Surveillance\/WeeklyReport\/202603\/P020260306355575921368.pdf."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"445","DOI":"10.1097\/INF.0000000000002178","article-title":"Influenza-associated Hospitalization in Children Younger Than 5 Years of Age in Suzhou, China, 2011\u20132016","volume":"38","author":"Yu","year":"2019","journal-title":"Pediatr. Infect. Dis. J."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"e13352","DOI":"10.1111\/irv.13352","article-title":"Incidence of Hospitalization due to Influenza-Associated Severe Acute Respiratory Infection During 2010\u20132019 in Bangladesh","volume":"18","author":"Ahmed","year":"2024","journal-title":"Influenza Other Respir. Viruses"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"ofw262","DOI":"10.1093\/ofid\/ofw262","article-title":"Risk Factors for Influenza-Associated Severe Acute Respiratory Illness Hospitalization in South Africa, 2012\u20132015","volume":"4","author":"Tempia","year":"2017","journal-title":"Open Forum Infect. Dis."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"e642","DOI":"10.1093\/infdis\/jiaf164","article-title":"Influenza-Associated Hospitalization Rates by Underlying Conditions, 2016\u20132017 to 2019\u20132020: A Retrospective Cohort Study","volume":"232","author":"Frutos","year":"2025","journal-title":"J. Infect. Dis."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"873","DOI":"10.1016\/j.jiac.2018.07.013","article-title":"Influenza vaccine showed a good preventive effect against influenza-associated hospitalization among elderly patients, during the 2016\/17 season in Japan","volume":"24","author":"Seki","year":"2018","journal-title":"J. Infect. Chemother."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1196","DOI":"10.1093\/infdis\/jiaa493","article-title":"Influenza Vaccination and Hospitalization Outcomes Among Older Patients With Cardiovascular or Respiratory Diseases","volume":"223","author":"Pang","year":"2021","journal-title":"J. Infect. Dis."},{"key":"ref_12","unstructured":"World Health Organization (2026, May 05). WHO Information for the Molecular Detection of Influenza Viruses. Available online: https:\/\/cdn.who.int\/media\/docs\/default-source\/influenza\/molecular-detention-of-influenza-viruses\/protocols_influenza_virus_detection_2024.pdf."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"1314","DOI":"10.1093\/ije\/dyl162","article-title":"Methods for monitoring influenza surveillance data","volume":"35","author":"Cowling","year":"2006","journal-title":"Int. J. Epidemiol."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"1853","DOI":"10.1016\/j.vaccine.2019.02.013","article-title":"The effectiveness of influenza vaccination in preventing hospitalizations in elderly in Beijing, 2016\u201318","volume":"37","author":"Zhang","year":"2019","journal-title":"Vaccine"},{"key":"ref_15","first-page":"2600096","article-title":"Modest protection from vaccination against influenza A(H3N2) subclade K, Beijing, China, 2025\/26 season","volume":"31","author":"Shen","year":"2026","journal-title":"Eurosurveillance"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"2500854","DOI":"10.2807\/1560-7917.ES.2025.30.46.2500854","article-title":"Early influenza virus characterisation and vaccine effectiveness in England in autumn 2025, a period dominated by influenza A(H3N2) subclade K","volume":"30","author":"Kirsebom","year":"2025","journal-title":"Eurosurveillance"},{"key":"ref_17","first-page":"2500992","article-title":"Interim vaccine effectiveness against influenza virus among outpatients, France, October 2025 to January 2026","volume":"31","author":"Blanquart","year":"2026","journal-title":"Eurosurveillance"},{"key":"ref_18","first-page":"1507","article-title":"Technical guidelines for seasonal influenza vaccination in China (2023\u20132024)","volume":"44","author":"Peng","year":"2023","journal-title":"Zhonghua Liu Xing Bing Xue Za Zhi"},{"key":"ref_19","unstructured":"The Joint Committee on Vaccination and Immunisation (JCVI) (2026, February 04). JCVI Statement on Influenza Vaccines for 2025 to 2026, Available online: https:\/\/www.gov.uk\/government\/publications\/flu-vaccines-2025-to-2026-jcvi-advice\/jcvi-statement-on-influenza-vaccines-for-2025-to-2026."},{"key":"ref_20","unstructured":"European Centre for Disease Prevention and Control (2026, March 10). Survey Report on National Seasonal Influenza Vaccination Recommendations and Coverage Rates in EU\/EEA Countries, 2024\/25. Available online: https:\/\/www.ecdc.europa.eu\/sites\/default\/files\/documents\/seasonal-influenza-recommendation-coverage-2025.pdf."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"msaf227","DOI":"10.1093\/molbev\/msaf227","article-title":"Seasonal Influenza Viruses Show Distinct Adaptive Dynamics During Growth in Chicken Eggs","volume":"42","author":"Kistler","year":"2025","journal-title":"Mol. Biol. Evol."},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Ortiz de Lejarazu-Leonardo, R., Montomoli, E., Wojcik, R., Christopher, S., Mosnier, A., Pariani, E., Trilla Garcia, A., Fickenscher, H., G\u00e4rtner, B.C., and Jandhyala, R. (2021). Estimation of Reduction in Influenza Vaccine Effectiveness Due to Egg-Adaptation Changes\u2014Systematic Literature Review and Expert Consensus. Vaccines, 9.","DOI":"10.3390\/vaccines9111255"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"635","DOI":"10.1056\/NEJMoa1315727","article-title":"Efficacy of High-Dose versus Standard-Dose Influenza Vaccine in Older Adults","volume":"371","author":"DiazGranados","year":"2014","journal-title":"N. Engl. J. Med."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"5027","DOI":"10.1016\/j.vaccine.2014.07.013","article-title":"Comparison of the safety and immunogenicity of an MF59\u00ae-adjuvanted with a non-adjuvanted seasonal influenza vaccine in elderly subjects","volume":"32","author":"Frey","year":"2014","journal-title":"Vaccine"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"6122","DOI":"10.1016\/j.vaccine.2013.07.059","article-title":"The comparative effectiveness of adjuvanted and unadjuvanted trivalent inactivated influenza vaccine (TIV) in the elderly","volume":"31","author":"Konrad","year":"2013","journal-title":"Vaccine"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"e4251","DOI":"10.1093\/cid\/ciaa1727","article-title":"Comparative Effectiveness of Influenza Vaccines Among US Medicare Beneficiaries Ages 65 Years and Older During the 2019\u20132020 Season","volume":"73","author":"Izurieta","year":"2021","journal-title":"Clin. Infect. Dis."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"88","DOI":"10.1016\/j.arbres.2015.09.001","article-title":"Prevalence of Influenza Vaccination in Chronic Obstructive Pulmonary Disease Patients and Impact on the Risk of Severe Exacerbations","volume":"52","author":"Garrastazu","year":"2016","journal-title":"Arch. Bronconeumol."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"1065","DOI":"10.1093\/cid\/ciad679","article-title":"Influenza Vaccine Effectiveness Pre-pandemic Among Adults Hospitalized With Congestive Heart Failure or Chronic Obstructive Pulmonary Disease and Older Adults","volume":"78","author":"Tippett","year":"2024","journal-title":"Clin. Infect. Dis."}],"container-title":["Vaccines"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2076-393X\/14\/5\/457\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,5,20]],"date-time":"2026-05-20T09:51:31Z","timestamp":1779270691000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2076-393X\/14\/5\/457"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,5,20]]},"references-count":28,"journal-issue":{"issue":"5","published-online":{"date-parts":[[2026,5]]}},"alternative-id":["vaccines14050457"],"URL":"https:\/\/doi.org\/10.3390\/vaccines14050457","relation":{},"ISSN":["2076-393X"],"issn-type":[{"value":"2076-393X","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,5,20]]}}}