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Early #influenza virus characterisation and #vaccine #effectiveness in #England in autumn 2025, a period dominated by influenza #H3N2 subclade K

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By G.M.

 


Authors: Freja CM Kirsebom{1}, Catherine Thompson{2}, Tiina Talts{2}, Beatrix Kele{2}, Heather J Whitaker{3}, Nurin Abdul Aziz{1}, Christopher Rawlinson{1}, Rebecca E Green{1}, Catherine Quinot{1}, Nicholas Gardner{1}, Elizabeth Waller{1}, Alex Allen{1}, Conall H Watson{1,4}, Suzanna LR McDonald{1}, Maria Zambon{2}, Richard Pebody{4,5}, Mary Ramsay{6,7}, Katja Hoschler{2}, Anika Singanayagam{*2,4}, Jamie Lopez Bernal{*1,4} 

{*} Joint last authors 

{1} Immunisation and Vaccine-preventable Diseases Division, UK Health Security Agency, Colindale, London 

{2} Respiratory Virus Unit (RVU), UK Health Security Agency, Colindale, London 

{3} Modelling Division, UK Health Security Agency, Colindale, London 

{4} NIHR Health Protection Research Unit in Respiratory Infections, Imperial College London, United Kingdom 

{5} Epidemic and Emerging Infections Directorate, UK Health Security Agency, Colindale, London 

{6} Public Health Programmes Directorate, UK Health Security Agency, Colindale, London 

{7} NIHR Health Protection Research Unit in Immunisations, London School of Hygiene and Tropical Medicine, United Kingdom 


Abstract  

Influenza A(H3N2) subclade K (J.2.4.1) has dominated the start of the 2025 to 2026 influenza season in England. We found reduced reactivity of subclade K with post-infection ferret antisera raised against the Northern Hemisphere 2025 to 2026 vaccine strains, aligning with World Health Organization reports. Nevertheless, vaccine effectiveness against hospital attendance and admission in the early season currently remains within a typical range at 70 to 75% in children and 30 to 40% in adults. Our data indicates that vaccination remains an effective preventative tool against circulating influenza A(H3N2). 

Source: United Kingdon Health Security Agency, https://www.gov.uk/government/publications/pre-print-early-influenza-virus-characterisation-and-vaccine-effectiveness-in-england-in-autumn-2025

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