Inclusion Criteria:  Patients ≥18 years on chronic dialysis due to end-stage renal disease. Competence to understand the study rationale, including potential risks and benefits associated with treatment, necessary for written informed consent.  Exclusion Criteria:  Prior verified SARS-CoV-2 infection. Hypersensitivity reaction to chloroquine, hydroxychloroquine or 4-aminoquinolines Electrocardiogram with QTc (Bazett's formula) > 450 ms in males and 460 ms in females Patients reliant on digoxin or amiodarone treatment Pre-existing psoriasis Any pre-existing maculopathy with vision reduction Prior sensorineural hearing loss Pre-existing severe liver insufficiency (spontaneous international normalized ratio >1.5 within the last year) Pre-existing epileptic disease requiring anti-epileptic medication Pregnancy or lactation Insurmountable Language Barrier Participation in other ongoing intervention trials investigating COVID19-related outcomes