- Severe Covid-19 defined as NEWS-2 score >5 or admission to the ICU needing ventilation or pressure support. - Contra-indications for hydroxychloroquine or chloroquine- Known pregnancy, not using adequate contraception and having a chance of being pregnant (unless a negative pregnancy test is documented) or breast-feeding- Unable to take oral medication (chloroquine and hydroxychloroquine can be administered through tube feeding and is considered oral administration)- Identified allergies to 4-aminoquinoline- Severe diseases of the blood system - 6-phosphate dehydrogenase deficiency - History of acute myocardial infarction, unstable angina pectoris, severe arrhythmia (frequent ventricular, ventricular tachycardia, ventricular fibrillation) in recent 6 months, New York Heart Association (NYHA) level III-IV- Corrected QT interval (QTc) = 480ms on baseline electrocardiogram. (The treatment guideline states: An electrocardiogram is made before start chloroquine and hydroxychloroquine)- Uncorrected severe hypokalaemia (< 2,5 mmol/l) or uncorrected severe hypomagnesemia (< 0.6 mmol/l) - Pancreatitis- Concomitant medication that affect drug absorption, metabolism and excretion, that can induce QT interval prolongation: o Amiodarone, disopyramide, flecainide, ibutailide, kinidine, sotalol, o chlorpromazine, citolapram, escitalopram, haloperidol, pimozide, o azitromycine, claritromycine, erytromycine, moxifloxacine, trimethoprim/sulfamethoxazole, o Dimperidon, ondansetron,o Methadon, o Anagrelide, arseentrioxide, droperidol, pentamidine, sevofluraan, vandetanib. - Refusal to participate expressed by patient or legally authorized representative if they are present

- Severe Covid-19 defined as NEWS-2 score >5 or admission to the ICU needing ventilation or pressure support. - Contra-indications for hydroxychloroquine or chloroquine- Known pregnancy, not using adequate contraception and having a chance of being pregnant (unless a negative pregnancy test is documented) or breast-feeding- Unable to take oral medication (chloroquine and hydroxychloroquine can be administered through tube feeding and is considered oral administration)- Identified allergies to 4-aminoquinoline- Severe diseases of the blood system - 6-phosphate dehydrogenase deficiency - History of acute myocardial infarction, unstable angina pectoris, severe arrhythmia (frequent ventricular, ventricular tachycardia, ventricular fibrillation) in recent 6 months, New York Heart Association (NYHA) level III-IV- Corrected QT interval (QTc) = 480ms on baseline electrocardiogram. (The treatment guideline states: An electrocardiogram is made before start chloroquine and hydroxychloroquine)- Uncorrected severe hypokalaemia (< 2,5 mmol/l) or uncorrected severe hypomagnesemia (< 0.6 mmol/l) - Pancreatitis- Concomitant medication that affect drug absorption, metabolism and excretion, that can induce QT interval prolongation: o Amiodarone, disopyramide, flecainide, ibutailide, kinidine, sotalol, o chlorpromazine, citolapram, escitalopram, haloperidol, pimozide, o azitromycine, claritromycine, erytromycine, moxifloxacine, trimethoprim/sulfamethoxazole, o Dimperidon, ondansetron,o Methadon, o Anagrelide, arseentrioxide, droperidol, pentamidine, sevofluraan, vandetanib. - Refusal to participate expressed by patient or legally authorized representative if they are present