On Apr. 9, 2020, the first participants were enrolled in the trial at Vanderbilt University Medical Center, Nashville, one of dozens of centers in the PETAL Network. The blinded, placebo-controlled randomized clinical trial planned to enroll more than 500 adults who are currently hospitalized with COVID-19 or in an emergency department with anticipated hospitalization. All participants in the study received clinical care as indicated for their condition. Those randomized to the experimental intervention also received hydroxychloroquine.