From the COVID-19 Response, Centers for Disease Control and Prevention (L.R.F., E.B.R., J.P.C., M.W.T., M.M.P.), and the Division of Critical Care Medicine, Department of Pediatrics (K.M.T.), the Department of Pediatrics, Division of Infectious Diseases (P.J.), and the Department of Pediatrics, Division of Cardiology (M.E.O.), Emory University School of Medicine, Atlanta; Public Health Service Commissioned Corps, Rockville (L.R.F., E.B.R., M.M.P.), and the Department of Anesthesiology and Critical Care Medicine, Division of Pediatric Anesthesiology and Critical Care Medicine, Johns Hopkins School of Medicine, Baltimore (B.J.R.) - both in Maryland; the Department of Pediatrics, Division of Pediatric Critical Care, Bristol-Myers Squibb Children's Hospital, Robert Wood Johnson Medical School, Rutgers University (S.M. Horwitz), the Department of Pediatrics, Division of Population Health, Quality, and Implementation Sciences (PopQuIS), Rutgers Robert Wood Johnson Medical School (L.C.K.), New Brunswick, the Department of Pediatrics, Division of Pediatric Cardiology, Children's Hospital of New Jersey, Newark Beth Israel, Newark (R.F.W.), the Division of Hospital Medicine, Department of Pediatrics, Hackensack University Medical Center, Hackensack (K.N.C.), and the Division of Pediatric Critical Care, Department of Pediatrics, Saint Barnabas Medical Center, Livingston (S.J.G.) - all in New Jersey; the Department of Anesthesiology, Critical Care and Pain Medicine (M.M.N., A.G.R.), the Division of Immunology (M.B.F.S.), and the Department of Cardiology (J.W.N.), Boston Children's Hospital, and the Departments of Pediatrics (M.B.F.S., J.W.N., A.G.R.) and Anaesthesia (A.G.R.), Harvard Medical School, Boston, and the Department of Pediatrics, Pediatric Critical Care, Baystate Medical Center, Springfield (K.L.M.) - both in Massachusetts; the Department of Pediatrics, Division of Pediatric Critical Care Medicine, Central Michigan University, Detroit (S.M. Heidemann, A.A.M.); the Pediatric Critical Care Division, Maria Fareri Children's Hospital at Westchester Medical Center and New York Medical College, Valhalla (A.R.S., S.L.), Pediatric Critical Care Medicine, Department of Pediatrics, Icahn School of Medicine at the Mount Sinai Kravis Children's Hospital (S.P.Z., J.G.), the Division of Pediatric Infectious Diseases, Departments of Pediatrics and Microbiology, New York University Grossman School of Medicine (A.J.R.), Pediatric Critical Care, New York City Health and Hospitals, Kings County Hospital (M.A.K., H.A.), the Division of Pediatric Critical Care, Department of Pediatrics, SUNY Downstate Health Sciences University (S.D.), and the Department of Pediatrics, Division of Pediatric Critical Care, Maimonides Children's Hospital (A.D.), New York - all in New York; the Division of Critical Care, Department of Anesthesiology and Critical Care, University of Pennsylvania Perelman School of Medicine, Philadelphia (J.C.F.); the Department of Pediatrics, Division of Critical Care, Yale University School of Medicine, New Haven (J.S.G., A.G.), and the Division of Critical Care, Connecticut Children's, Hartford (R.M.P., C.L.C.) - both in Connecticut; the Department of Pediatrics, Section of Critical Care Medicine, University of Colorado School of Medicine and Children's Hospital Colorado, Aurora (A.B.M.); the Division of Pediatric Critical Care Medicine, Department of Pediatrics, Advocate Children's Hospital, Chicago (V.H., S.R.); the Department of Pediatrics, Division of Pediatric Rheumatology, MetroHealth Medical Center, Case Western Reserve University (H.B.), and the Division of Pediatric Hospital Medicine, Rainbow Babies and Children's Hospital (A.L.), Cleveland; the Department of Pediatrics, Division of Cardiology, Louisiana State University Health Sciences Center and Children's Hospital of New Orleans, New Orleans (T.T.B.); the Department of Pediatrics, Division of Pediatric Critical Care Medicine, University of Washington, Seattle (L.S.S.); the Pediatric Critical Care Division, Department of Pediatrics, University of Texas Health Science Center at Houston, Houston (A.C.M.); the Department of Pediatrics, Department of Microbiology, Division of Infectious Diseases, University of Mississippi Medical Center, Jackson (C.V.H.); and the Division of Pediatric Infectious Diseases, Department of Pediatrics, Vanderbilt University Medical Center, Nashville (N.B.H.).