ArticleJournal of the Association of Medical Microbiology and Infectious Disease Canada = Journal officiel de l'Association pour la microbiologie medicale et l'infectiologie Canada2025
Emergence of seasonal influenza A(H3N2) variants with immune escape potential warrants enhanced molecular and epidemiological surveillance for the 2025-2026 season.
Article in Journal of the Association of Medical Microbiology and Infectious Disease Canada = Journal officiel de l'Association pour la microbiologie medicale et l'infectiologie Canada, 2025. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 22 papers.
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Who cites it
22 citing papers in PubMed.
- Reduced T cell epitope cross-conservation and immunogenic potential is associated with emergence of a dominant influenza subclade K in 2025.Human vaccines & immunotherapeutics · 2026Article
- Molecular Characterization of Influenza A(H3N2) Hemagglutinin Variants Circulating in Western Mexico, 2022.International journal of molecular sciences · 2026Article
- Loss of hemagglutination ability by H3N2 influenza A virus, subclade K.bioRxiv : the preprint server for biology · 2026Article
- Seasonal vaccine-induced immunity shows preserved cross-reactivity to H3N2 subclade K in adults.EBioMedicine · 2026Article
- Interim 2025/26 LP.8.1 vaccine effectiveness estimates against COVID-19 from the Canadian Sentinel Practitioner Surveillance Network (SPSN): insights into possible impact of influenza and other respiratory virus co-circulation.Euro surveillance : bulletin Europeen sur les maladies transmissibles = European communicable disease bulletin · 2026Article
- Influenza A(H3N2) Subclade K: Epidemiology, Molecular Evolution and Vaccine Effectiveness in Europe.Pathogens (Basel, Switzerland) · 2026Review
- Article
- Predictive modeling of influenza strain drugs using temperature-based topological indices and regression analysis via multi-criteria decision making techniques.Scientific reports · 2026Article
- Article
- Emergence of influenza A(H3N2) subclade K in northeast Ohio in autumn 2025.Journal of clinical microbiology · 2026Article
- AMMI Canada seasonal influenza guideline update 2025-26: Some questions answered.Journal of the Association of Medical Microbiology and Infectious Disease Canada = Journal officiel de l'Association pour la microbiologie medicale et l'infectiologie Canada · 2026Article
- Article
- Near real-time data on the human neutralizing antibody landscape to influenza virus as of early 2026 to inform vaccine-strain selection.bioRxiv : the preprint server for biology · 2026Article
- Seasonal vaccine-induced immunity shows preserved cross-reactivity to H3N2 subclade K in adults.medRxiv : the preprint server for health sciences · 2026Article
- Article
- Reduced neutralising antibody responses against emerging 2025/26 influenza A(H1N1)pdm09 subclade D.3.1 and A(H3N2) subclade K viruses among healthcare workers, Finland, August to October 2025.Euro surveillance : bulletin Europeen sur les maladies transmissibles = European communicable disease bulletin · 2026Article
- Interim 2025/26 influenza vaccine effectiveness estimates with immuno-epidemiological considerations for A(H3N2) subclade K protection, Canada, January 2026.Euro surveillance : bulletin Europeen sur les maladies transmissibles = European communicable disease bulletin · 2026Article
- Influenza vaccine effectiveness from nine studies during drifted A(H3N2) subclade K predominance, Europe, September 2025 to January 2026.Euro surveillance : bulletin Europeen sur les maladies transmissibles = European communicable disease bulletin · 2026Article
- Influenza A/H3N2 epidemiology in England during the 2025 to 2026 season: a mathematical modelling study.Communications health · 2026Article
- Near real-time data on the human neutralizing antibody landscape to influenza virus as of early 2026 to inform vaccine-strain selection.Virus evolution · 2026Article
Corrections and comments
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Authors and funding
7 authors.
Funding
No grant is acknowledged in the PubMed record.
Abstract
Background: All of the major antigenic changes in influenza A(H3N2) viruses since 1968 have involved mutations at just nine amino acid positions, called cluster transition sites, surrounding the receptor binding region of the hemagglutinin surface protein. During the Northern Hemisphere (NH) 2024-2025 influenza season, A(H3N2) variants emerged with multiple parallel substitutions affecting cluster transition sites 135, 145, 158, and/or 189, with implications for the 2025-2026 season. Methods: Using >24,000 global A(H3) sequences between September 2024 and August 2025, we assessed the nature and frequency of amino acid mutations among emerging NH and Southern Hemisphere (SH) A(H3N2) variants relative to the 2024-2025 subclade J and updated 2025-2026 subclade J.2 vaccine reference strains. We contextualized based on historic amino acid variation among >210,000 global A(H3) sequences since 1968 and publicly available antigenic characterization data relative to 2024-2025 and 2025-2026 vaccine reference strains. Results: Virtually all circulating A(H3N2) viruses in 2024-2025 were subclade J.2. In Europe, about one-third had cluster transition site mutations, mostly T135A with S145N. In North America, more than two-thirds had cluster transition site mutations, including T135K or S145N, with a late-season increase in doubly mutated J.2.3 (N158K + K189R) and J.2.5 (S145N + N158K) subclades. The SH 2025 season showed an increase in J.2.3 and emergence of J.2.4 (T135K + K189R), including a further drifted J.2.4.1 variant with additional N158D and other mutations, recently renamed subclade K. A substantial proportion of J.2.3 and J.2.4 viruses are antigenically distinct from the 2025-2026 influenza vaccine. Conclusion: Influenza A(H3N2) variants with a combination of cluster transition site mutations emerged during the NH 2024-2025 season. A further drifted and vaccine-mismatched variant, called subclade K, arose during the SH 2025 season and is projected to predominate among A(H3N2) viruses for the NH 2025-2026 season. While mismatched vaccines can still provide protection, enhanced genetic, antigenic, and epidemiological (eg, vaccine effectiveness, disease burden) monitoring are warranted to inform risk assessment and response.
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