In addition to the inactivated influenza vaccine (IIV), the live attenuated influenza vaccine (LAIV) has recently been recommended in some countries. We aimed to compare the protective impact of the IIV and LAIV against medically attended influenza infection. This retrospective study included participants aged 2-17 y who underwent influenza testing. The LAIV and IIV groups consisted of participants who received the respective vaccines between 6 months and 14 d before influenza testing. Propensity score matching was conducted to evaluate the odds ratio (OR) for medically attended influenza infection. Overall, 693 and 29,548; 523 and 26,395; and 510 and 24,471 participants in the LAIV and IIV groups were identified for the 2024-2025, 2023-2024, and 2022-2023 seasons, respectively. The ORs for medically attended influenza infection after receiving the LAIV versus the IIV were 0.97 (95% confidence interval 0.78-1.22; p = .818), 1.58 (1.17-2.13; p = .003), 1.09 (0.80-1.47; p = .590) for the 2024-2025, 2023-2024, and 2022-2023 seasons, respectively. The comparative impact of the LAIV and IIV on the prevention of influenza infection among children aged 2-17 y varied according to the epidemic season. Continuous monitoring of the vaccine effectiveness is critical.
Kitano et al. (Wed,) studied this question.