Influenza vaccination coverages in Italy from 1999/00 to 2023/24: A joinpoint regression analysis

Abstract

Background: Influenza is a contagious respiratory viral infection with significant health and economic impacts, causing millions of cases and hundreds of thousands of deaths annually worldwide. In Italy, annual epidemics affect approximately 8 % of the population. Vaccination remains the most effective prevention strategy, yet coverage in Italy is low and consistently below the WHO-recommended threshold of 75 % in elderly. This study aims to analyze trends in influenza vaccination coverage in Italy from 1999/2000 to 2023/2024 through joinpoint regression analysis.

Methods: Data on influenza vaccination coverage were obtained from the Italian Ministry of Health, covering the general population and specific age groups. The analysis included data from the 1999/2000 season to the 2023/2024 season. Joinpoint regression was used to identify significant changes in coverage trends over time, calculating Annual Percentage Change (APC) and Average Annual Percent Change (AAPC).

Results: Coverages vary between and within age groups over the study period. The pediatric population showed the lowest values, never exceeding 10 % except for the COVID-19 pandemic years. Similar trends, albeit with higher coverage, were observed in the adult population. In the elderly population, the WHO target of 75 % was never reached, obtaining the highest value of 68.3 % in 2005/2006. Trends show increasing AAPC coverages for all groups except 15-17 years. During the pandemic, increases in coverages are observed in all age groups, but these decline towards pre-pandemic values during the following seasons.

Conclusions: Our study shows that vaccination coverage in Italy falls below target thresholds, particularly in high-risk age groups, with a significant decreasing trend observed in the years following the pandemic across almost all age groups. Despite the proven efficacy and safety of the vaccine, hesitancy has gained momentum in Italy, resulting in persistently low coverage rates. Our findings highlight the need for a multifaceted approach, including expanding free vaccination programs, implementing school-based initiatives, strengthening healthcare worker engagement, and enhancing public awareness campaigns. A coordinated national effort, led by the Ministry of Health, is essential to achieving higher coverage rates and reducing the burden of influenza.

Keywords: Flu; Influenza; Joinpoint regression; Public Health; Trend analysis; Vaccination.