[Epidemiological approaches to address key research questions on COVID-19-an overview]

Epidemiology as a scientific discipline is predestined to address key problems in the COVID-19 pandemic. In order to do so, classic and new methods are used, and new challenges are emerging.This paper addresses the various phases of the population-based progression of SARS-CoV‑2 infection and COVID-19. Based on a selective literature search, sample questions from studies conducted in Germany and internationally are presented, their respective epidemiological approaches discussed, and research gaps described.Scientific questions to be answered with epidemiological data and research approaches arise in every phase of infection and disease. Descriptive data are often generated via (repeated) cross-sectional studies. For analytical questions, such as the identification of risk groups, case-control studies could have provided valuable results, especially in the early phase of the pandemic, but were rarely conducted. Data from health insurance companies have an important function in the analysis of the course of disease; however, the potential of this data source with regard to questions on vaccination can probably hardly be used. Improved coordination of the various studies and a more "open data" oriented research infrastructure can further strengthen the contribution of epidemiology to the control of the current and future pandemics.