Prevalence of chronic conditions and influenza vaccination coverage rates in Germany: Results of a health insurance claims data analysis

Background The significant annual burden caused by seasonal influenza has led to global calls for increased influenza vaccination coverage rates (VCRs). We aimed to estimate the proportion of the German population at high risk of serious illness from influenza due to chronic conditions and to estimate age-specific VCRs of people with/without chronic conditions. Methods Using health insurance claims data covering nine influenza seasons (2010-2019), we assessed up to 7 million insured individuals per season across all German regions. Individuals were classified according to age and presence of chronic health conditions. VCRs were estimated using outpatient healthcare utilization documentation. Results In the 2018-2019 influenza season, 47.3% of individuals had >= 1 chronic condition. Most common were circulatory disorders, accounting for more than a third of individuals with >= 1 condition. Prevalence of chronic diseases, and therefore the proportion of high-risk individuals, increased slightly over time across most age groups. A downward trend in influenza VCRs was observed in all age groups until the 2017-2018 season, followed by a noticeable increase in the 2018-2019 season. Highest VCRs occurred among individuals of >= 60 years, with a 38.5% VCR for this age group in the 2018-2019 season. Several factors, including age, chronic condition type, and geographical location, affected VCRs. Conclusions Influenza VCRs in individuals at high risk of severe complications from influenza infection are insufficient. Our results suggest that intensified public health efforts are necessary to reach the World Health Organization vaccination coverage target of 75%.