This a single-center, double-blinded, placebo-controlled, randomized, clinical trial to test if hydroxychloroquine post exposure prophylaxis (hPEP) reduces the symptomatic secondary attack rate of COVID-19 among close contacts of known or suspected COVID-19 patients. Enrolled subjects will be currently asymptomatic adults (=18 years old) currently residing in the same household as an index case [i.e. an individual evaluated at NYP via outpatient, emergency department (ED), or inpatient services who (1) tests positive for COVID-19, or (2) are defined as suspected cases, or persons under investigations (PUI)] without exclusions. Enrolled subjects will be randomized 1:1 to take a 5-day course of hydroxychloroquine sulfate (brand name, Plaquenil) or identical placebo. The dose will be 400 mg twice daily on day 1 and 200 mg twice daily on days 2-5. Enrolled subjects will receive periodic phone calls over 14 days to query symptoms and side effects. Those with new symptoms of COVID-19 infection will be directed to obtain testing for SARS-CoV-2. The primary endpoint of the trial will be symptomatic, lab-confirmed COVID-19 over the two-week follow-up. A number of secondary endpoints related to the severity of COVID-19 among household contacts will be explored. The trial will enroll 1600 subjects (800 per arm) and is powered to detect a 30%, or greater, reduction in the risk of symptomatic COVID-19.
