Vaccine effectiveness against medically attended, laboratory-confirmed influenza in the I-MOVE primary care network in Europe, VEBIS project, 2024/25

We conducted a multicenter test-negative study to estimate vaccine effectiveness (VE) against medically attended, laboratory-confirmed influenza in primary care, Europe, 2024/25. Specimens were collected from patients with acute respiratory infection. All or a random sample of viruses were sequenced. VE was (1-odds ratio) × 100, adjusted for confounders. We included 7275 cases and 17,516 controls (weeks 40–2024–18–2025). The overall VE was 46% (95% CI: 40–52), lowest in adults ≥65 years at 28% (95% CI: 12–42). VE against influenza A(H1N1)pdm09 was 30% (95% CI: 19–40); ranging 16–34% by age and vaccination target group. Most (88%) circulating clades were 5a.2a, distinct from the vaccine clade. VE was 28% (95% CI: 7–45) against 5a.2a (C.1.9), and 6% (95% CI: −62–45) against the vaccine-matched clade 5a.2a.1 (D). VE against influenza A(H3N2) was 38% (95% CI: 26–49); ranging 20–66% by age and target group. Circulating viruses belonged to the vaccine clade 2a.3a.1, with 88% subclade (J.2). VE against influenza B was 76% (95% CI: 69–81); ranging 70–80% by age and target group; all viruses belonged to the vaccine clade V1A.3a.2, with diverse subclades. Influenza vaccination protected approximately one in two vaccinated individuals against medically attended infection in primary care in Europe, 2024/25, varying by (sub)type and age.