Study population and setting
Authors considered all reported COVID-19 cases among individuals aged 10-49 in Germany during two periods: March 2-15, 2020; and March 23-April 4, 2020. Cases were stratified into 5-year age groups, and relative risks were calculated for being a detected case in a given age group during the later period versus the earlier period.
Summary of Main Findings
There were changes in the age structure of cases between periods: cases were less likely in the later period to be at the youngest and oldest ends of the age spectrum. Cases were more likely to be in the 20-24 year age group in the later period relative to the earlier period (RR=1.40, 95% CI: 1.27,1.55). Cases were less likely to be in the 10-14 years(0.78 [0.64,0.95]), 40-44 years (0.90 [0.83,0.98]), and 45-49 years (0.83 [0.77,0.89]) groups.
The methodology is easily replicable in other populations and time periods.
The age structure of reported case counts may not reflect the relative importance of those groups in driving transmission, let alone differential uptake of social distancing: possible confounding factors include the rollout of testing in different communities, changes in health-seeking behavior that vary by age, and spatial/geographical features of epidemic growth.
The study offers a simple but straightforward approach to examining temporal trends in the age structure of the COVID-19 epidemic.