Population immunity, post-vaccine and post-infection antibody responses to influenza A (H3N2) subclade J.2 and K (J.2.4.1) viruses, Hong Kong, 2025

Eurosurveillance 2026 Open access

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Authors: Samuel MS Cheng, Nancy HL Leung, Eunice Y Shiu, Rwk Wong, Niki YM Au, X.R. Huang, Natalie KM Kwok, Coco HC Chan, Jin Li, Leo C.H. Tsang, Tsz Chun Kwan, KL Tsang
+3 more Leo LM Poon, Benjamin J Cowling, Malik Peiris
DOI: 10.2807/1560-7917.es.2026.31.10.2600185
Cited by: 2
References: 6

Abstract

We assessed haemagglutination inhibition (HAI) antibody titres against 2025 influenza A(H3N2) J.2 vaccine reference viruses and the novel subclade K (J.2.4.1) in age-stratified Hong Kong sera (collected May-July 2025), vaccine recipients and sera from virologically confirmed subclade J.2.2 or K infections. In contrast to mono-specific ferret sera, human sera with high J.2 HAI titres cross-reacted strongly with subclade K. Recombinant haemagglutinin- or egg-based standard dose J.2 A(H3N2) vaccines boosted geometric mean titres to K virus 5.6-fold and 2.6-fold, respectively.

Fields of Study & Subjects

Influenza Virus Research Studies Respiratory viral infections research interferon and immune responses

Publication details

Journal / source
Eurosurveillance
Publisher
European Centre for Disease Control and Prevention (ECDC)
Volume
31
Issue
10
Publication date
12 March 2026
Language
EN