On Nov. 25, 2020, the National Institute of Allergy and Infectious Diseases (NIAID), one of the National Institutes of Health, announced that the fourth iteration of the Adaptive COVID-19 Treatment Trial (ACTT-4) had begun to enroll hospitalized adults with coronavirus disease 2019 (COVID-19) who required supplemental oxygen. The NIAID-sponsored trial planned to enroll up to 1,500 patients at approximately 100 sites in the U.S. and other countries.