Background: This is a single-center prospective active-surveillance study to assess the incidence, patient characteristics and outcome of myocardial inflammation/myocarditis after COVID-19 booster vaccination. By utilizing high-sensitivity troponin T (hs-cTnT), we aim to detect cases that are too mild or too early in stage to be detected with a less sensitive approach. BASEC ID: 2021-02339 Sponsor: University Hospital Basel, Switzerland Trial Status: Enrollment closed Enrolling Centers: University Hospital Basel Core Study Team: