Modest protection from vaccination against influenza A(H3N2) subclade K, Beijing, China, 2025/26 season

Eurosurveillance 2026 Open access

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Authors: Ying Shen, Daitao Zhang, Zhaomin Feng, Chunna Ma, Weixian Shi, Wei Duan, Jia Li, Lu Zhang, Dan Wu, J J Zhang, Jiaxin Ma, Y. Wang
+10 more Xiaodi Hu, Shuning Yan, Yuanzhi Di, Jiachen Zhao, Hui Xu, Guilan lu, Yimeng Liu, Weijia Zhang, Quanyi Wang, Peng Yang
DOI: 10.2807/1560-7917.es.2026.31.7.2600096
Cited by: 2
References: 16

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.

Fields of Study & Subjects

Influenza Virus Research Studies Respiratory viral infections research SARS-CoV-2 and COVID-19 Research

Publication details

Journal / source
Eurosurveillance
Publisher
European Centre for Disease Control and Prevention (ECDC)
Volume
31
Issue
7
Publication date
19 February 2026
Language
EN