This study consists of 2 parts: a longitudinal study enrolling 3,000 health care professionals at the Vienna General Hospital testing their antibody status 6 times over a period of 12 months (Cohort A), and a serial cross-sectional study of 3,000 patients (i.e., a total of 9,000 patients) admitted to the Vienna General Hospital for non-COVID-19-related symptoms at 3 different time points during this pandemic (Cohort B).
