Influenza A(H3N2) Subclade K: Epidemiology, Molecular Evolution and Vaccine Effectiveness in Europe [PDF]
PathogensBackground: Influenza A(H3N2) viruses remain a major public health concern due to their rapid antigenic evolution and association with severe disease, particularly among high-risk populations.
Irene Scarvaglieri +7 more
doaj +5 more sources
Seasonal vaccine-induced immunity shows preserved cross-reactivity to H3N2 subclade K in adultsResearch in context [PDF]
EBioMedicineSummary: Background: Influenza A subclade K viruses caused high infection rates in the 2025/2026 Northern Hemisphere season, raising concerns about antigenic drift and reduced vaccine effectiveness.
Adria Wilson +18 more
doaj +6 more sources
Extended influenza seasons in Australia and New Zealand in 2025 due to the emergence of influenza A(H3N2) subclade K viruses [PDF]
EurosurveillanceIn Australia and New Zealand, late outbreaks of an A(H3N2) variant virus termed subclade K extended the 2025 influenza season. Subclade K viruses were genetically and antigenically distinct from the 2025 vaccine A(H3N2) strain A/Croatia/10136RV/2023 ...
Ian G. Barr
exaly +6 more sources
First detection and transatlantic introduction of Influenza A(H3N2) subclade K (J.2.4.1) into Ecuador: insights from genomic sentinel surveillance [PDF]
Frontiers in Public HealthBackgroundThe rapid evolution of Influenza A(H3N2) requires constant global monitoring. This study analyzes the genomic characteristics and the first introduction of the emerging subclade K (J.2.4.1) in Ecuador, utilizing publicly available data to trace
Alfredo Bruno +7 more
doaj +4 more sources
Influenza vaccine effectiveness from nine studies during drifted A(H3N2) subclade K predominance, Europe, September 2025 to January 2026 [PDF]
EurosurveillanceThe European 2025/26 influenza season is dominated by the influenza A(H3N2) virus, with most sequenced viruses belonging to subclade K, genetically drifted from the vaccine virus, raising concerns around vaccine effectiveness (VE).
the European IVE group
doaj +7 more sources
Early influenza virus characterisation and vaccine effectiveness in England in autumn 2025, a period dominated by influenza A(H3N2) subclade K [PDF]
EurosurveillanceInfluenza A(H3N2) subclade K (J.2.4.1) has dominated the 2025/26 season start in England. Post-infection ferret antisera raised against northern hemisphere 2025/26 vaccine strains showed reduced reactivity to subclade K viruses in England, aligning with ...
Jamie Lopez Bernal
exaly +7 more sources
Emergence of influenza A(H3N2) subclade K in northeast Ohio in autumn 2025 [PDF]
Journal of Clinical MicrobiologyHannah Wang, Daniel D. Rhoads, Ted Ross
exaly +6 more sources
Assessment of human immunity to A/H3N2 influenza subclade K during 2025 emergenceResearch in context [PDF]
EBioMedicineSummary: Background: Seasonal influenza causes significant morbidity and mortality annually. In 2025, the genetically divergent A/H3N2 K subclade (J.2.4.1) emerged with substantial haemagglutinin mutations.
Ruth Harvey +46 more
doaj +3 more sources
Reduced T cell epitope cross-conservation and immunogenic potential is associated with emergence of a dominant influenza subclade K in 2025 [PDF]
Human Vaccines & ImmunotherapeuticsSubclade K is a newly emergent influenza A/H3N2 strain that became the dominant strain circulating globally; more than 90% of influenza A virus (IAV) cases in 2025–26 were subclade K.
Andres H. Gutierrez +3 more
doaj +3 more sources
Modest protection from vaccination against influenza A(H3N2) subclade K, Beijing, China, 2025/26 season [PDF]
EurosurveillanceDuring 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 ...
Peng Yang
doaj +4 more sources