Additional Study Information: The HERO program has two parts: the HERO Registry and the HERO-HCQ Trial. The HERO Registry is asking hundreds of thousands of U.S. healthcare professionals to join, including nurses, therapists, physicians, emergency responders, food service workers, environmental services workers, interpreters, and transporters anyone who works in a setting where people receive health care. Its goals are to understand healthcare workers experiences and interests and to track critical health outcomes associated with caring for patients with COVID-19, such as stress and burnout. The HERO-HCQ Trial is a randomized clinical trial of approximately 15,000 U.S. healthcare workers. It will evaluate whether hydroxychloroquine (brand name Plaquenil) can prevent COVID-19 infection in healthcare workers. The trial will randomize participants to either one month of hydroxychloroquine or one month of placebo. To take part in the HERO study, healthcare workers must first join the HERO Registry. Healthcare workers who participate in HERO-HCQ will receive a $50 Visa gift card as a thank you at the end of the study. You can learn more about and join the HERO Registry by visiting: https://heroesresearch.org/