Comparative effectiveness of live attenuated influenza vaccine (LAIV) and inactivated influenza vaccine (IIV) in children over multiple influenza seasons (2019–2023)

Vaccine effectiveness (VE) of quadrivalent live attenuated influenza vaccine (LAIV4) and quadrivalent inactivated influenza vaccine (IIV4) in children in 13 European countries and the US during the 2019–2023 influenza seasons was evaluated from published literature, congress presentations, public health websites, and personal communications with investigators. A meta-analysis was performed by assessing LAIV4 and/or IIV4 VE in children ( N = 34–1679) across included studies during the 2019/20–2022/23 seasons. VE estimates against influenza infection (all strains) for LAIV4 were 61.9 % (95 % confidence interval [CI]: 53.0–69.1) and for IIV4 were 45.7 % (33.2–55.8). Overall VE (95 % CI) for individual strains for the 2022/23 season for LAIV4 were 75.7 % (52.0–87.7) and for IIV4 were 58.5 % (38.2–72.1). Overall, LAIV4 and IIV4 VE in children was moderate and comparable. Annual vaccination with LAIV4 or IIV4 remains the best way to protect children against influenza infection. • A meta-analysis assessed LAIV4 and IIV4 VE in children from 2019 to 2023. • VE against influenza infection (all strains) was 61.9 % for LAIV4 and 45.7 % for IIV4. • Individual strain VE in the 2022/23 season was 75.7 % for LAIV4 and 58.5 % for IIV4. • VE for LAIV4 and IIV4 in children was moderate and comparable across seasons.