The impact of changes in age-based eligibility criteria on seasonal influenza vaccine uptake in England between 2019 and 2024: A retrospective cohort study

The study examined the impact of changes in age-based eligibility criteria on seasonal influenza vaccine uptake in England between 2019 and 2024. The research included 1.2 to 1.3 million people aged 40 to 69 years with clinical risk factors. In the 2020/21 season, vaccine uptake increased across all age groups, with the largest increase among those aged 50 to 64 years (13.3%). From 2020/21 to 2022/23, vaccine uptake declined, with a more pronounced decrease among those aged 40 to 49 years (5.4%) compared with age-eligible groups. When original age-based criteria were reinstated in the 2023/24 season, vaccine uptake among those aged 50 to 64 years fell by 9.6%. The findings suggest that expanded age-based eligibility criteria can increase influenza vaccine coverage among clinical risk groups.