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Expression of concern

Abstract

[An expression of concern for this article was published on 16 January 2026.]

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 September and December 2025. Among 9,579 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 41.3% (95% CI: 29.2 to 51.3), indicating moderate protection during this subclade K-dominated season.

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/content/10.2807/1560-7917.ES.2026.31.2.2500993
2026-01-15
2026-02-07
/content/10.2807/1560-7917.ES.2026.31.2.2500993
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[Expression of concern published on 16 January 2026]
Moderate protection from vaccination against influenza A(H3N2) subclade K in Beijing, China, September to December 2025
<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=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>. [Expression of concern published on 16 January 2026]
Moderate protection from vaccination against influenza A(H3N2) subclade K in Beijing, China, September to December 2025. <a href="/content/ecdc">Euro Surveill.</a> 2026;31(2):pii=2500993. <a href="https://doi.org/10.2807/1560-7917.ES.2026.31.2.2500993" title="doi link" target="_blank">https://doi.org/10.2807/1560-7917.ES.2026.31.2.2500993</a> <span class="ES_Article_citation"> <span class="generated">Received</span>: 27 Dec 2025;&nbsp;&nbsp; <span class="generated">Accepted</span>: 14 Jan 2026 </span> </p>
/content/10.2807/1560-7917.ES.2026.31.2.2500993
/content/10.2807/1560-7917.ES.2026.31.2.2500993
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