1887
  1. Home
  2. Eurosurveillance
  3. Volume 31, Issue 7, 19/Feb/2026
  4. Article
Rapid communication Open Access
Like 0
Download

Abstract

During the early 2025/26 influenza season, influenza A(H3N2) subclade K rapidly predominated in Beijing, China. Using a test-negative design, we estimated influenza vaccine effectiveness (VE) among influenza-like illness outpatients tested between weeks 40/2025 and 04/2026. Among 10,484 participants, sequencing of 316 randomly selected A(H3N2)-positive samples showed 84.8% were subclade K, and antigenic analysis of 65 viruses indicated antigenic divergence. Despite this, adjusted VE against laboratory-confirmed influenza was 23.5% (95% confidence interval: 11.7–33.7), indicating modest protection during this subclade K-dominated season.

© Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Loading

Article metrics loading...

/content/10.2807/1560-7917.ES.2026.31.7.2600096
2026-02-19
2026-03-15
/content/10.2807/1560-7917.ES.2026.31.7.2600096
Loading
Loading full text...

Full text loading...

/deliver/fulltext/eurosurveillance/31/7/eurosurv-31-7-3.html?itemId=/content/10.2807/1560-7917.ES.2026.31.7.2600096&mimeType=html&fmt=ahah

References

  1. Fieldhouse R. Japan declares a flu epidemic - what this means for other nations. Nature. 2025; Online ahead of print.  https://doi.org/10.1038/d41586-025-03367-z  PMID: 41087518 
  2. Zambon M, Hayden FG. Influenza A (H3N2) subclade K virus: threat and response. JAMA. 2026;335(4):307-10.  https://doi.org/10.1001/jama.2025.25903  PMID: 41411120 
  3. Schweitzer K. A new H3N2 influenza strain is raising concerns about this flu season. JAMA. 2026;335(3):199-200.  https://doi.org/10.1001/jama.2025.25205  PMID: 41417267 
  4. World Health Organization (WHO). Recommended composition of influenza virus vaccines for use in the 2025- 2026 northern hemisphere influenza season seasonal influenza activity. Geneva: WHO; 2025. Available from: https://cdn.who.int/media/docs/default-source/influenza/who-influenza-recommendations/vcm-northern-hemisphere-recommendation-2025-2026/recommended-composition-of-influenza-virus-vaccines-for-use-in-the-2025-2026-northern-hemisphere-influenza-season.pdf?sfvrsn=857c2e9b_13&download=true
  5. World Health Organization (WHO). Recommended composition of influenza virus vaccines for use in the 2026 southern hemisphere influenza season. Geneva: WHO; 2025. Available from: https://cdn.who.int/media/docs/default-source/influenza/who-influenza-recommendations/vcm-sh-2025/a.-26-september-2025-recommended-composition-of-influenza-virus-vaccines-for-use-in-the-2026-southern-hemisphere-influenza-season---full-report.pdf?sfvrsn=eba6ad63_5&download=true
  6. Kirsebom FC, Thompson C, Talts T, Kele B, Whitaker HJ, Andrews N, et al. Early influenza virus characterisation and vaccine effectiveness in England in autumn 2025, a period dominated by influenza A(H3N2) subclade K. Euro Surveill. 2025;30(46):2500854.  https://doi.org/10.2807/1560-7917.ES.2025.30.46.2500854  PMID: 41267661 
  7. European Centre for Disease Prevention and Control (ECDC). Early estimates of seasonal influenza vaccine effectiveness against influenza requiring medical attention at primary care level in Europe, week 41 - 49, 2025. Stockholm: ECDC; 2025. Available from: https://www.ecdc.europa.eu/en/news-events/early-estimates-seasonal-influenza-vaccine-effectiveness-against-influenza-requiring
  8. De Clercq A, Blanquart F, Vieillefond V, Visseaux B, Jacques A, Haim-Boukobza S, et al. Interim vaccine effectiveness against influenza virus among outpatients, France, October 2025 to January 2026. Euro Surveill. 2026;31(2):2500992.  https://doi.org/10.2807/1560-7917.ES.2026.31.2.2500992  PMID: 41540925 
  9. Sun Y, Shi W, Zhang D, Ma C, Feng Z, Zhang J, et al. Early vaccine effectiveness estimates against medically attended laboratory-confirmed influenza based on influenza surveillance, Beijing, China, 2024/25 season. Euro Surveill. 2025;30(7):2500084.  https://doi.org/10.2807/1560-7917.ES.2025.30.7.2500084  PMID: 39980425 
  10. Adams K, Weber ZA, Yang DH, Klein NP, DeSilva MB, Dascomb K, et al. Vaccine effectiveness against pediatric influenza-A-associated urgent care, emergency department, and hospital encounters during the 2022-2023 season: VISION network. Clin Infect Dis. 2024;78(3):746-55.  https://doi.org/10.1093/cid/ciad704  PMID: 37972288 
  11. Kissling E, Pozo F, Martínez-Baz I, Buda S, Vilcu AM, Domegan L, et al. Influenza vaccine effectiveness against influenza A subtypes in Europe: Results from the 2021-2022 I-MOVE primary care multicentre study. Influenza Other Respir Viruses. 2023;17(1):e13069.  https://doi.org/10.1111/irv.13069  PMID: 36702797 
  12. Shen Y, Feng Z, Zhang D, Wang X, Sun Y, Li F, et al. Mitigated transmission and health impact of COVID-19 in Beijing, China during spring 2024: Comparison with the global trends. Sci Bull (Beijing). 2024;69(20):3212-5.  https://doi.org/10.1016/j.scib.2024.07.047  PMID: 39209599 
  13. Zhang J, Zhang L, Li J, Ma J, Wang Y, Sun Y, et al. Moderate effectiveness of influenza vaccine in outpatient settings: A test-negative study in Beijing, China, 2023/24 season. Vaccine. 2025;46:126662.  https://doi.org/10.1016/j.vaccine.2024.126662  PMID: 39731809 
  14. Zhang L, Lu G, Ma C, Zhang J, Li J, Duan W, et al. Influenza vaccine effectiveness against influenza A-associated outpatient and emergency-department-attended influenza-like illness during the delayed 2022-2023 Season in Beijing, China. Vaccines (Basel). 2024;12(10):1124.  https://doi.org/10.3390/vaccines12101124  PMID: 39460291 
  15. Separovic L, Sabaiduc S, Zhan Y, Kaweski SE, Olsha R, Hasso M, et al. Interim 2025/26 influenza vaccine effectiveness estimates with immuno-epidemiological considerations for A(H3N2) subclade K protection, Canada, January 2026. Euro Surveill. 2026;31(5):2600068.  https://doi.org/10.2807/1560-7917.ES.2026.31.5.2600068  PMID: 41645799 
  16. DiazGranados CA, Dunning AJ, Kimmel M, Kirby D, Treanor J, Collins A, et al. Efficacy of high-dose versus standard-dose influenza vaccine in older adults. N Engl J Med. 2014;371(7):635-45.  https://doi.org/10.1056/NEJMoa1315727  PMID: 25119609 
  17. Johansen ND, Modin D, Loiacono MM, Harris RC, Dufournet M, Larsen CS, et al. High-dose influenza vaccine effectiveness against hospitalization in older adults. N Engl J Med. 2025;393(23):2291-302.  https://doi.org/10.1056/NEJMoa2509907  PMID: 40888720 
  18. Van Buynder PG, Konrad S, Van Buynder JL, Brodkin E, Krajden M, Ramler G, et al. The comparative effectiveness of adjuvanted and unadjuvanted trivalent inactivated influenza vaccine (TIV) in the elderly. Vaccine. 2013;31(51):6122-8.  https://doi.org/10.1016/j.vaccine.2013.07.059  PMID: 23933368 
  19. Lee JKH, Lam GKL, Shin T, Samson SI, Greenberg DP, Chit A. Efficacy and effectiveness of high-dose influenza vaccine in older adults by circulating strain and antigenic match: An updated systematic review and meta-analysis. Vaccine. 2021;39(Suppl 1):A24-35.  https://doi.org/10.1016/j.vaccine.2020.09.004  PMID: 33422382 
Modest protection from vaccination against influenza A(H3N2) subclade K, Beijing, China, 2025/26 season
<p class="citation"> <span>Citation style for this article:</span> <span class="meta-value authors"> <a href="/search?value1=Ying+Shen&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Shen Ying</a>, <a href="/search?value1=Daitao+Zhang&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Zhang Daitao</a>, <a href="/search?value1=Zhaomin+Feng&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Feng Zhaomin</a>, <a href="/search?value1=Chunna+Ma&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Ma Chunna</a>, <a href="/search?value1=Weixian+Shi&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Shi Weixian</a>, <a href="/search?value1=Wei+Duan&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Duan Wei</a>, <a href="/search?value1=Jia+Li&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Li Jia</a>, <a href="/search?value1=Lu+Zhang&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Zhang Lu</a>, <a href="/search?value1=Dan+Wu&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Wu Dan</a>, <a href="/search?value1=Jiaojiao+Zhang&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Zhang Jiaojiao</a>, <a href="/search?value1=Jiaxin+Ma&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Ma Jiaxin</a>, <a href="/search?value1=Yingying+Wang&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Wang Yingying</a>, <a href="/search?value1=Xiaodi+Hu&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Hu Xiaodi</a>, <a href="/search?value1=Shuning+Yan&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Yan Shuning</a>, <a href="/search?value1=Yuanzhi+Di&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Di Yuanzhi</a>, <a href="/search?value1=Jiachen+Zhao&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Zhao Jiachen</a>, <a href="/search?value1=Hui+Xu&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Xu Hui</a>, <a href="/search?value1=Guilan+Lu&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Lu Guilan</a>, <a href="/search?value1=Yimeng+Liu&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Liu Yimeng</a>, <a href="/search?value1=Weijia+Zhang&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Zhang Weijia</a>, <a href="/search?value1=Quanyi+Wang&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Wang Quanyi</a>, <a href="/search?value1=Peng+Yang&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Yang Peng</a></span>. Modest protection from vaccination against influenza A(H3N2) subclade K, Beijing, China, 2025/26 season. <a href="/content/ecdc">Euro Surveill.</a> 2026;31(7):pii=2600096. <a href="https://doi.org/10.2807/1560-7917.ES.2026.31.7.2600096" title="doi link" target="_blank">https://doi.org/10.2807/1560-7917.ES.2026.31.7.2600096</a> <span class="ES_Article_citation"> <span class="generated">Received</span>: 02 Feb 2026;&nbsp;&nbsp; <span class="generated">Accepted</span>: 13 Feb 2026 </span> </p>
/content/10.2807/1560-7917.ES.2026.31.7.2600096
/content/10.2807/1560-7917.ES.2026.31.7.2600096
Loading

Data & Media loading...

Supplementary data

Submit comment
Close
Comment moderation successfully completed
This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error