Influenza vaccine effectiveness in children shows moderate, broad protection during the 2024-2025 season

Presented by

Ms Giulia Di Lucchio , AstraZeneca, Italy

Conference

ESCMID Vaccines 2025

Real-world vaccine effectiveness of influenza vaccines in children and adolescents aged <18 years ranged from 55-57% in European countries and the USA for the 2024-2025 season, with similar effectiveness among influenza subtypes, according to a meta-analysis presented by Ms Giulia Di Lucchio (AstraZeneca, Italy) at the ESCMID Vaccines 2025 conference.

The vaccines included in the study were live attenuated influenza vaccine (LAIV) and inactivated influenza vaccine (IIV). Interim vaccine effectiveness estimates from identified studies were pooled using random-effects meta-analysis, and estimates were provided overall and by influenza subtype. Continuous analyses were carried out until May 2025 to cover the 2024-2025 season.

Five studies were identified (totalling 10 European countries and the USA) that provided 34 interim estimates of vaccine effectiveness (11 for LAIV and 23 for IIV). Overall, interim vaccine effectiveness was estimated at 55% (95% CI 47-62) for LAIV and 57% (95% CI 42-68) for IIV. Among serotypes, vaccine effectiveness was estimated at 50% (95% CI 34–62) and 55% (95% CI 34–69) for A/H1N1, and 76% (95%CI 55–87) vs 69% (95%CI 27–87) for influenza B. For A/H3N2, data were less precise, with estimates of 44% (95 %CI -529 to 95) and 37% (95% CI 17–53), respectively. End-of-season UK data were available for LAIV and showed similar overall vaccine effectiveness.

“This analysis provides an early assessment of vaccine effectiveness in the 2024–2025 influenza season, a season largely driven by influenza A/H1N1,” said Ms Di Lucchio. “We saw moderate protection against influenza, 55-60%, which was similar and comparable for the two vaccines. Point estimates suggested higher effectiveness for influenza B and lower effectiveness for A/H3N2. Finally, we saw that end-of-season estimates from the UK were broadly similar to the pooled interim vaccine effectiveness.”

Enxing J, et al. Effectiveness of the live attenuated (LAIV) and inactivated (IIV) influenza vaccines in children: a meta-analysis of interim data (based on cases through February 2025) from the 2024/25 influenza season. 6^th ESCMID Vaccines, 10–13 September 2025, Lisbon, Portugal.

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