Epidemiology can be described as an interface between public health, basic medical sciences, and clinical medicine which aims to maximize the benefit of existing knowledge in these areas. Epidemiology identifies weak links in the chains, sources, and transmission pathways of emerging novel pathogens such as SARS-CoV-2 so that the interventions can be directed appropriately. Epidemiological studies are essential to understand the incidence and prevalence of emerging infectious diseases, as well as their clinical characteristics and risk factors. These data are essential to assess the feasibility of clinical field efficacy and effectiveness trials and to support trial design of promising vaccine candidates. Epidemiological research can also help strengthen site and investigator capacity to conduct clinical trials as well as support and inform national governments in their public health response to emerging infectious diseases and to implement the appropriate medical countermeasures.