Temporal rise in the proportion of both younger adults and older adolescents among COVID-19 cases in Germany: evidence of lesser adherence to social distancing practices?

Edward Goldstein; Marc Lipsitch

In this paper, we apply the methodology in [5, 6] to assess the relative roles of different age groups during the early stage of the 2020 SARS-CoV-2 epidemic in Germany using data on COVID-19 cases publicly available from the Robert Koch Institute [7] . The idea of this approach (a generalization of the original approach in [5, 6] ) is that age groups that have an elevated role in propagating an epidemic will have their share among all incident cases increase with time during the early states of the epidemic, particularly under containment efforts for which adherence varies between the different age groups. For example, if contact rates for one age group are less affected by social distancing measures compared to another age group due to lesser adherence, incidence of infection in the former age group will increase relative to the latter. This, in particular, can happen if the initial period of a study begins soon after the social distancing measures are implemented (which is the case for our study), with the shares of different age groups in incidence during the initial period being affected by the corresponding shares before the implementation of social distancing measures. Additionally, if a given country comprises several regions with different growth rates for their epidemics, the age group that drives the incidence of infection in regions with faster growing/larger epidemics will have its share among all incident cases in the country increase with time.