biostudies-literatureUnknown31(2)De Clercq AIn Europe, the 2025/26 seasonal influenza epidemic started in October 2025. Co-circulation of A(H3N2) and A(H1N1)pdm09 was observed in several countries including France. We estimated early vaccine effectiveness (VE) against influenza virus in French outpatients (5,451 positives/18,816 negatives). A significant VE across all age groups was measured: 28% (95% CI: 17-37) for those aged ≥ 65 years, 45% (95% CI: 36-53) for 18-64-year-olds and 57% (95% CIs: 29-74) for 0-17-year-olds. Reinforcing vaccination uptake is warranted.Euro surveillance : bulletin Europeen sur les maladies transmissibles = European communicable disease bulletinhttps://www.ebi.ac.uk/biostudies/studies/S-EPMC12811705biostudies-literatureInterim vaccine effectiveness against influenza virus among outpatients, France, October 2025 to January 2026.PMC12811705Duret TPerez-Bercoff DDe Clercq ABal AJacques AWehrle VVisseaux BJosset LVieillefond VRameix-Welti MARELAB study groupEnouf VLina BBlanquart FDeleglise GHaim-Boukobza SBernard-Stoecklin SOblette AfalseInterim vaccine effectiveness against influenza virus among outpatients, France, October 2025 to January 2026.In Europe, the 2025/26 seasonal influenza epidemic started in October 2025. Co-circulation of A(H3N2) and A(H1N1)pdm09 was observed in several countries including France. We estimated early vaccine effectiveness (VE) against influenza virus in French outpatients (5,451 positives/18,816 negatives). A significant VE across all age groups was measured: 28% (95% CI: 17-37) for those aged ≥ 65 years, 45% (95% CI: 36-53) for 18-64-year-olds and 57% (95% CIs: 29-74) for 0-17-year-olds. Reinforcing vaccination uptake is warranted.2026-01-01T00:00:00Z2026 Jan2026-06-14T06:13:21.139Z2026-06-14T03:16:46.802ZS-EPMC128117054154092510.2807/1560-7917.ES.2026.31.2.2500992