Treatment of COVID-19 Cases and Chemoprophylaxis of Contacts as Prevention

Study 1: Inclusion Criteria for a contact: 1. Asymptomatic individuals exposed to a PCR confirmed COVID19 case within 7 days as either a healthcare worker or household contact 2. Aged ≥18 years male or female; 3. In women of childbearing potential, negative pregnancy test and commitment to use contraceptive method throughout the study. 4. Willing to take study medication; 5. Willing to comply with all study procedures; 6. Able to provide oral, informed consent and/or assent. Exclusion Criteria for a contact: 1. With known history of cardiac arrhythmia (or QT prolongation syndrome); 2. Unable to take drugs by mouth; 3. With significantly abnormal liver function (Child Pugh C) 4. Need of dialysis treatment, or GFR≤30 mL/min/1.73 m2; 5. Participants with psoriasis, myasthenia, haematopoietic and retinal diseases,CNS-related hearing loss or glucose-6-phosphate dehydrogenase deficit; 6. Persons already treated with any of the study drugs during the last 30 days; 7. Pregnant or lactating women; 8. Any contraindications as per the Data Sheet of Hydroxychloroquine. Study 2: Inclusion Criteria for a case: 1. Patients who meet the requirements of the New Coronavirus Infection Diagnosis (Acute \<5 days respiratory infection symptoms, or fever alone, or acute cough alone and positive PCR) 2. Aged ≥18 years male or female; 3. In women of childbearing potential, negative pregnancy test and commitment to use contraceptive method throughout the study. 4. Willing to take study medication 5. Willing to comply with all study procedures, including repeat nasal swab at day 3 6. Able to provide oral and written informed consent Exclusion Criteria for a case: 1. Hospital admission 2. Serious condition meeting one of the following: (1) respiratory distress with respiratory rate \>=30 breaths/min; (2) oxygen saturation\<=93% on quiet status; (3) Arterial partial pressure of oxygen (PaO2)/oxygen concentration\<=300mmHg; 3. Critically ill patients meeting one of the following: (1) Experience respiratory failure and need to receive mechanical ventilation; (2) Experience shock; (3) Complicated with other organs failure and need intensive care and therapy in ICU; 4. Participants under treatment with medications likely to interfere with experimental drugs 5. Unable to take drugs by mouth; 6. With significantly abnormal liver function (Child Pugh C) 7. Need of dialysis treatment, or GFR≤30 mL/min/1.73 m2; 8. Participants with psoriasis, myasthenia, haematopoietic and retinal diseases,CNS-related hearing loss or glucose-6-phosphate dehydrogenase deficit 9. Participants with severe neurological and mental illness; 10. Pregnant or lactating women; 11. Inability to consent and/or comply with study protocol; 12. Individuals with known hypersensitivity to the study drugs. 13. Persons already treated with any of the study drugs during the last 30 days. 14. Any contraindications as per the Data Sheet of Hydroxychloroquine.