Near real-time data on the human neutralizing antibody landscape to influenza virus in summer of 2026 shows antigenic advance of H3N2 subclade K region D mutants and H1N1 D.3.1.1 Sa mutants

In April–August 2026, neutralization titers against 148 seasonal influenza strains show reduced serum neutralization for H3N2 subclade K antigenic region D mutants and H1N1 subclade D.3.1.1 antigenic region Sa mutants, with 52,268 titers measured.

• Why it matters: Twice-yearly vaccine strain updates require near real-time evidence on how circulating influenza antigenically shifts relative to human immunity, especially as new variants emerge.
• What they did: Using high-throughput sequencing-based neutralization assays, the study measured 52,268 titers from 355 human sera collected between April and August 2026 against 148 viral strains.
• The result: New H3N2 subclade K region D mutations and H1N1 subclade D.3.1.1 region Sa mutations (including G155E) are linked to reduced neutralization, with heterogeneity across individuals, enabling improved vaccine antigen selection and viral evolution analyses.

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