inclusion criteria: - health-care worker with frequent contact with confirmed covid-19 patients - no active or past infection with sars-cov-2 - 18 years of age or older - no allergy or contraindication to hydroxychloroquine - written informed consent

inclusion criteria: - health-care worker with frequent contact with confirmed covid-19 patients - no active or past infection with sars-cov-2 - 18 years of age or older - no allergy or contraindication to hydroxychloroquine - written informed consent