Influenza vaccine effectiveness in an Italian elderly population during the 2016-2017 season.

Interim analyses of the 2016-17 influenza vaccine effectiveness showed variable results depending on timing of the analysis and geographical setting. We conducted a population-based retrospective cohort study based on the analysis of health-related administrative data to assess the effectiveness of the 2016-17 influenza vaccine among the elderly population of a north-eastern Italian area. Data on 64854 subjects ≥65 years of age were analyzed up to April 30, 2017. The influenza vaccine was administered to 53% of the elderly population. No significant effect was observed on the likelihood of Emergency department visits, hospitalizations, or deaths from pneumonia and influenza.