1. Centers for Disease Control and Prevention COVID-19 Response Team, Atlanta, Georgia (I.S., A.L., P.M., N.K.T., K.R.B., R.G., A.I.G., K.A.J., S.S., T.T.S., J.R.S., D.K.S.)
2. The Johns Hopkins University, Baltimore, Maryland (M.B.S., K.R.T., V.C.U., J.C.Y.)
3. Vanderbilt University Medical Center, Nashville, Tennessee (A.P.W., K.M.E., S.C.W.)
4. Food and Drug Administration, Center for Biologics Evaluation and Research, Silver Spring, Maryland (E.J.W., A.M.)
5. Duke University School of Medicine, Durham, North Carolina (E.B.W., T.L.O.)
6. Columbia University Irving Medical Center, New York, New York (I.J.A.).