Medical Risk Classification For Severe COVID-19 Based On Chronic Medical Conditions: A Comparative Analysis

Background: The European Centre for Disease Prevention and Control (ECDC) provides listings of medical conditions conferring high- or moderate-risk for severe COVID-19. In addition, individual European countries developed their own risk classifications for severe COVID-19 to select individuals recommended for annual COVID-19 vaccination. We assessed the discordance between the European and respective national medical risk classifications in assigning children and adults to risk groups for developing severe COVID-19 in populations of the Netherlands and Norway.

Methods: This multi-country, healthcare data-linkage study covered 17.4 million inhabitants of the Netherlands and 5.6 million inhabitants of Norway by 1 January 2020. Medical conditions were defined based on ICD-10 hospital discharge codes in the European and Dutch classifications, and on ICD-10 and
ICPC-2 primary care codes in the Norwegian classification. Subjects were classified as high-, moderate-, or low-risk. Discordance was calculated as the proportion of the population with a different risk status in the respective national compared to the European classification.
Findings: The overall discordance between European and national risk classification was 12.0% in the Dutch and 13.8% in the Norwegian population. The European classification assigns more individuals to high-risk (9.0% and 9.2% of the Dutch and Norwegian populations, respectively) than the national
classifications (1.5% and 3.0%, respectively). National classifications define more individuals as moderate-risk (11.3% and 12.7%, respectively) than the European classification (1.0% and 1.3%, respectively). Classification discordances most frequently involved subjects with cardiovascular disease, lung disease, and diabetes mellitus.

Interpretation: The European classification defines a substantially larger percentage of the population as high-risk for severe COVID-19 than the national classifications. This may have implications for post pandemic vaccination programs. Further research should assess to what extent the medical conditions responsible for the classification discordances determine the risk of developing severe COVID-19.