During the COVID-19 pandemic several countries have seen a high risk of transmission for health care personnel, with some countries having as many 20-25% of nurses and doctors either infected or showing symptoms of COVID-19. In this prospective cohort study, we will systematically screen all hospital staff in the Capital Region of Denmark for IgM and IgG antibodies against SARS-CoV-2 using a point of care tests and an Elisa kit. Testing will be offered 3 times: In April 2020, Maj 2020 and September 2020. All participants will submit a questionnaire regarding exposures, risk factors and symptoms of COVID-19 in relation to each testing. Follow-up will be through electronic patient records and national registries. We will compare the group of health care personnel with data from a control group of healthy volunteer blood donors from the Danish Blood Donor Study. The aim of the study is to investigate the proportion of hospital staff with SARS-CoV-2 antibodies during the study period compared to a control group representing the Danish population. We will compare the test characteristics of the two methods of testing, a point of care test and Elisa. Further, we will investigate the extent to which prior immunization or infection is protective for future infection with COVID-19.