Safety And Efficacy Of Hydroxychloroquine For At Risk Population (SHARP) Against COVID-19

Inclusion criteria: 1. Aged 18 to 80 years. 2. History of close contact or exposure to positive COVID-19 cases in the same household. 3. Absence of symptoms resembling COVID-19 (e.g., fever and acute respiratory or gastrointestinal symptoms) for two weeks prior to enrolment for the study. 4. Able to give informed consent or in case of \<21 and\>/=18 years old subject, parents able to give consent for those individuals. In the event the household is unable to read or sign/date the ICF, an impartial witness to be present to ascertain the information, comprehension and voluntariness. The impartial witness must be able to read the informed consent form (ICF). 5. Able to comply with study procedures and follow-up 6. Singapore citizen, permanent resident or long-term pass-holder. Exclusion Criteria: 1. Person diagnosed with COVID-19 infection. 2. Pregnant at the time of screening or breastfeeding. 3. Known allergy or hypersensitivity to HCQ or other aminoquinoline compounds. 4. Already on HCQ for different indications (e.g., rheumatological diseases, malaria prophylaxis) 5. Diagnosis of other systemic viral or bacterial infection. 6. Use of systemic immunosuppressant agents within 90 days of enrollment (e.g., corticosteroids and immunomodulatory therapy) 7. History of immunocompromised state. 8. History of psychiatric illness. 9. History of psoriasis or porphyria. 10. History of cardiac disease. 11. Other major comorbidities that contraindicate the use of HCQ: i. Hematologic malignancy, ii. Stage 4-5 chronic kidney disease or end-stage renal failure, iii. history of ventricular arrhythmias, iv. current use of drugs that prolong the QT interval 12. History of severe skin reactions such as Stevens-Johnson syndrome and toxic epidermal necrolysis. 13. Bradycardia \<50beats/min. 14. Uncorrected hypokalemia 15. Uncorrected hypomagnesemia. 16. Unwillingness to practice acceptable methods of birth control (both males who have partners of childbearing potential and females of childbearing potential) while on study and for at least 30 days after last dose.