A systematic review and meta-analysis of the effectiveness of LAIV4 and IIV in children aged 6 months to 17 years during the 2016-2017 season.

As the real-world effectiveness of quadrivalent live attenuated influenza vaccine (LAIV4) and inactivated influenza vaccine (IIV) has varied in recent seasons, a systematic review and meta-analysis was conducted to more precisely estimate effectiveness in the 2016-2017 season. Relevant studies were identified from a systematic review of published literature and personal communication with study investigators. Five studies conducted in Canada, Finland, Germany, the United Kingdom, and the United States were identified for inclusion. Data were analyzed using a random effects model, with heterogeneity testing and a sensitivity analysis restricted to test-negative case-control studies. Consolidated vaccine effectiveness estimates against all strains were 69% (95% CI: 46 to 82) for LAIV4 and 47% (95% CI: 29 to 61) for IIV. Heterogeneity testing was not statistically significant, indicating consistency of individual study results. In conclusion, LAIV4 and IIV showed moderate and comparable effectiveness against influenza in children during the 2016-2017 influenza season.