Effectiveness of Influenza Vaccination in Children Aged 6-59 Months during the Inaugural 2022-2023 Season in Andalusia, Spain.

Abstract

To estimate the effectiveness of influenza vaccination when systematic vaccination against influenza was introduced for the first time in Andalusia for the children aged 6 through 59 months, an age group with one of the highest incidence and influenza-related hospitalization rates each season. Population-based, retrospective cohort study during the 2022-2023 influenza season of 287 661 children aged 6-59 months at the beginning of the inaugural 2022-2023 vaccination campaign. Adjusted vaccine effectiveness (VE) was calculated by estimating multivariable logistic regression models for likelihood of influenza diagnosis in vaccinated and unvaccinated children. In children aged 6-59 months, VE was 51% (95% CI: 48%-53%) for preventing infection and 69% (95% CI: 56%-79%) for preventing influenza-related hospitalization. In children aged 6-23 months, VE was 53% (95% CI: 48%-57%) for preventing influenza and 76% (95% CI: 57%-87%) for preventing hospitalization due to influenza. In both subpopulations, VE was significantly higher with the two-dose vaccination schedule. Influenza vaccination shows moderate effectiveness in preventing influenza and high effectiveness in preventing influenza-related hospitalization in children aged 6-59 months. This highlights the importance of strengthening influenza vaccination coverage in this age group.