Patients at high risk for a severe clinical course of COVID-19 — small-area data in support of vaccination and other population-based interventions in Germany

BACKGROUND: Research has shown that the risk for a severe course of COVID-19 is increased in the elderly population and among patients with chronic conditions. The aim of this study was to provide estimates of the size of vulnerable populations at high risk for a severe COVID-19 course in Germany based on the currently available risk factor data. METHODS: We used nationwide outpatient claims data from the years 2010 to 2019 collected according to § 295 of the Code of Social Law V, covering data for all statutory health insurees (SHI) which is nearly 87% of the entire German population. We considered 15 chronic disorders based on the current state of knowledge about clinically relevant risk factors. Three risk groups for a severe COVID-19 course were defined: 1. individuals in the age group 15 to 59 years with at least two comorbid disorders; 2. individuals aged 60 to 79 years with at least one disorder and 3. all individuals 80 years and older irrespective of the presence of chronic conditions. Regional analysis was conducted at the level of administrative districts (n = 401). RESULTS: Overall, 26% of individuals over 15 years were at high risk for a severe COVID-19 course in 2019 amounting to a total number of nearly 18.5 million individuals in Germany. This included 3.8 million individuals in risk group 1, 9.2 million in risk group 2, and 5.4 million in risk group 3, corresponding to 8, 50 and 100% of German inhabitants in the respective age groups. On the level of the 17 administrative regions formed by the Association of SHI Physicians (ASHIP regions), the proportion of individuals at high risk ranged between 21% in Hamburg and 35% in Saxony-Anhalt. Small-area estimates varied between 18% in Freiburg (Baden-Württemberg) and 39% in the district Elbe-Elster (Brandenburg). CONCLUSIONS: The present study provides small-area estimates of populations at high risk for a severe COVID-19 course. These data are of particular importance for planning of preventive measures such as vaccination. TRIAL REGISTRATION: not applicable. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12889-021-11735-3.