Influenza Vaccination Effectiveness in Paediatric 'Healthy' Patients: A Population-Based Study in Italy.

ABSTRACT

BACKGROUND: Seasonal influenza can cause serious morbidity, mortality, and financial burden in pediatric and adult populations. The influenza vaccine (IV) is considered the most effective way to prevent influenza and influenza-like-illness (ILI) complications. OBJECTIVE: To assess the effectiveness of the IV in a cohort of healthy children in Italy. METHODS: From the Pedianet database, all healthy children aged six months-14 years between 2009-2019 were enrolled. Cox proportional-hazards models were fitted to estimate hazard ratios and the 95% confidence interval for the association between IV exposure during each season of interest (from October to April of each year) with incident influenza/ILI. Exposure was considered as a time-varying variable. Vaccine effectiveness (VE) was calculated as (1-HR) × 100. The additive and prolonged effects of IV were evaluated across the seasons. RESULTS: We found a high IV effectiveness among healthy children. No additional or prolonged effects were found. CONCLUSION: Our data indicates that IV was effective in preventing influenza/ILI in healthy children. Therefore, IV should be encouraged and provided free of charge to healthy children in all the Italian regions every year, reducing disease spread and lowering the burden on the pediatric population.