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Subclade K #influenza A #H3N2 viruses display partial immune #escape with preserved cross-neutralisation in a #UK population

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By G.M.

 


Abstract

We examined whether the recent emergence of influenza A(H3N2) subclade K, associated with an unusually early influenza season in the Northern hemisphere, was accompanied by a reduction in human population immunity. Using virus neutralisation assays on pre-epidemic human sera collected in May 2025, we found evidence of moderate antigenic drift. Further, vaccines used in the 2024/2025 season induced cross-neutralising immunity. These findings provide timely insight for interpreting recent influenza epidemiology and informing vaccine strain selection.


Competing Interest Statement

The following authors declare no conflict of interests: KD, RI, LM, SR, HC, GGA, MSA, VS, ZW, SKW, JZ, BJW, DLR, JH, OML, JG, CJRI. PRM receives funding for research work for MSD. EH has received an honorarium for advisory board work for Seqirus. ET has received funding from Novavax and Astra Zeneca.


Funding Statement

This work was funded by the Medical Research Council (MRC) to the MRC-University of Glasgow Centre for Virus Research (grants MC_UU_0034/1, MC_UU_0034/2, MC_UU0034/3, MC_UU0034/5 and MC_UU0034/6). Funding to EH and PRM from the Medical Research Council (MRC) and Department for Environment, Food and Rural Affairs (Defra, UK) as FluTrailMap-One Health [MR/Y03368X/1] is also acknowledged.

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Link: https://www.medrxiv.org/content/10.64898/2026.01.27.26344933v1

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