In December 2019, a group of patients with pneumonia of unknown cause was identified in Wuhan, in the Hubei province, China. Despite the need of target specific therapeutic options for COVID-19, until now there is no proof of effectiveness of any specific intervention. Some limited observational trials and also evidence from randomized trials have shown no benefit of hydroxychloroquine in inpatient context. Thus, studies evaluating interventions in an outpatient setting in non-severe patients can provide important information related to prognosis and safety. In this way, the present study will evaluate the effectiveness and safety of the use of hydroxychloroquine in COVID-19 outpatients by means of a Randomized, double-blind, placebo-controlled trial

Pragmatic, double-blind, placebo-controlled randomized parallel-group, two-arm clinical trial (with allocation ratio 1:1), evaluating hydroxychloroquine (800 mg at 1st day, and 400 mg from day 2 to 7) for prevention of hospitalization and respiratory complications in non-hospitalized confirmed or suspected COVID-19 cases. Key inclusion criteria are adults (equal to or greater tahn 18 years) seeking medical care with suspected or confirmed COVID-19, with time between symptoms and inclusion ≤ 07 days, presenting mild symptoms, without indication of hospitalization and at least one risk factor for complication (> 65 years; hypertension; diabetes mellitus; asthma; Chronic Obstructive Pulmonary Disease (COPD) or other chronic lung diseases; smoking; immunosuppression; obesity (Defined as BMI equal to or greater than 30 Kg/m2). Primary endpoint is to assess if the treatment with hydroxychloroquine is able to avoid hospitalization due to a COVID-19-related clinical reason within 30 days of randomization in an outpatient setting. Hospitalization is considered to be hospital stay for a period > 24h or an additional hospitalized calendar day. The primary endpoint is centrally adjudicated by an independent clinical events committee blinded to the assigned treatment groups. Secondary endpoints include uncontrolled asthma after ≥ 5 days of starting study medication; pneumonia; otitis media; fever resolution time; time to improve respiratory symptoms; hospitalization in the Intensive Care Unit; need for orotracheal intubation; mechanical ventilation time; mortality. Safety outcomes will be hypoglycemia; palpitations; reduced visual acuity; diarrhea; anorexia; and emotional lability. The evaluation of the primary outcome (hospitalization within 30 days) will be performed for the included population following the principle of intention-to-treat (ITT), which will consist of all randomized cases. A modified intention-to-treat analysis (mITT), in which cases definitely confirmed as negative for COVID-19 will be excluded, will also be performed.

Inclusion Criteria:

It will be considered eligible those adults (equal to or greater than 18 years) seeking medical care with suspected or confirmed COVID-19, with time between symptoms and inclusion ≤ 07 days, presenting mild symptoms, without indication of hospitalization and at least 1 risk factor for complication:

1. > 65 years;
2. Hypertension;
3. Diabetes mellitus;
4. Asthma;
5. COPD or other chronic lung diseases;
6. Smoking;
7. Immunosuppression;
8. Obesity (Defined as BMI equal to or greater than 30 Kg/m2).

Exclusion Criteria:

1. Patients under 18 years old;
2. Hospitalization at the first medical care;
3. Positive test for influenza at the first medical care;
4. Known hypersensitivity to hydroxychloroquine / chloroquine;
5. Previous diagnosis of retinopathy or macular degeneration;
6. Previous diagnosis of Long QT-syndrome, history of sudden death in close family members (parents and siblings), decompensated heart failure, unstable coronary artery disease, use of anti-arrhythmic drugs or other drugs that can increase the hydroxychloroquine bioavailability or enhance its effect;
7. Evidence of known liver disease, reported by the patient;
8. Evidence of known chronic kidney disease, reported by the patient;
9. Patients with pancreatitis;
10. Baseline ECG with QTc interval ≥ 480ms;
11. Chronic use of hydroxychloroquine/chloroquine for other reasons;
12. Pregnancy.

Randomization (1:1) is generated by a validated software and performed in permuted blocks of size 8. Concealment of the randomization list is maintained through a 24-hour, centralized, automated, internet-based randomization system. Furthermore, as placebo-controlled study, the placebo will have the same structural characteristics as the active drug and will be dispensed in cartridges that do not allow the identification of what is being given