Healthcare Worker Exposure Response and Outcomes of Hydroxychloroquine

Inclusion: * Completed Informed Consent * Age ≥ 18 years old * Currently working in any environment in which there is a risk of exposure to patients with COVID-19 infections ("healthcare worker") Exclusion Criteria: * Prior diagnosis of COVID-19 infection * Participation in another COVID-19 prophylaxis trial within 30 days of consent * Respiratory illness with new-onset fever (Temperature \> 100°F) or ongoing cough or dyspnea within 14 days * Known allergy to HCQ or chloroquine * Congenital prolonged QT syndrome * Current or planned use of QT prolonging drugs (e.g. procainamide, disopyramide, mexiletine, flecainide, propafenone, amiodarone, sotalol, cimetidine, dronedarone, dofetilide, levofloxacin, ciprofloxacin, moxifloxacin) and other contraindicated medications * End stage renal disease * Pre-existing retinopathy * Current or planned use of Hydroxychloroquine (study drug) for any indication Current or planned use of the following for treatment or prevention of COVID-19 infection: * Chloroquine * Azithromycin * Known cirrhosis or severe liver disease * History of severe skin reactions such as Steven-Johnson syndrome, toxic epidermal necrolysis * History of psoriasis or porphyria * Ventricular arrhythmias requiring medical treatment * Severe coronary artery disease or heart failure/cardiomyopathy with ongoing symptoms * Current or planned use of use of anti-seizure drugs * History of Glucose-6-phosphate dehydrogenase deficiency