Background: In June and July 2025, a rapid increase in the incidence of influenza A(H3N2) subclade K raised awareness about a possible vaccine mismatch. We estimated the mid-season influenza vaccine effectiveness (IVE)
against laboratory-confirmed influenza in outpatient settings in the Community of Madrid for the 2025/26 season.
Methods: Individuals attending to primary care with acute respiratory infection (ARI) and tested for influenza were enrolled in the study. A test-negative design was used to calculate IVE.
Results: From week 40 of 2025 to week 2 of 2026, data from 763 ARI cases were included in the study. The adjusted IVE for gender, age, chronic diseases, month of onset, and RSV/COVID-19 coinfection was 52.74% (95%
CI: 13.67% to 74.13%) overall, 46.46% (95% CI: − 34.34% to 78.67%) for A(H1N1)pdm09 and 65.20% (95% CI: 18.92% to 85.06%) for A(H3N2).
Conclusions: Despite the suspected influenza vaccine mismatch, IVE for A(H3N2) type was high.
Autores: Macarena Garrido-Estepa; Luis García-Comas; Mercedes Rumayor-Zarzuelo; Juan Carlos Sanz-Moreno; Ana Garrido-Buenache; Susana Jiménez-Bueno; Rodrigo Martínez-Arce; Marta Huerta-Cofiño; Alba Nieto-Julia; María Araceli Arce-Arnáez
Vaccine: X 30 (2026) 100818