From the Center for Childhood Infections and Vaccines, Children's Healthcare of Atlanta, and the Department of Pediatrics, Emory University School of Medicine, Atlanta (E.J.A.), and IResearch Atlanta, Decatur (K.A.J.) - all in Georgia; the Vanderbilt Vaccine Research Program, Department of Pediatrics, Vanderbilt University Medical Center (C.B.C.), and Meharry Medical College (V.B.) - both in Nashville; OnSite Clinical Solutions, Charlotte, NC (A.P.); the Henry Ford Health System, Detroit (M.Z.); Pi-Coor Clinical Research, Burke, VA (F.G.); the Lynn Health Science Institute, Oklahoma City (C.G.); the Cyfair Clinical Research Center (K.P.) and the Texas Center for Drug Development (K.A.), Houston, and ACRC Trials, Frisco (M.A.) - all in Texas; Velocity Clinical Research, Meridian, ID (M.T.); Children's Hospital of Philadelphia Clinical Research Partners, Philadelphia (J.G.); Clinical Research Partners, Richmond, VA (R.L.B.); Clinical Research Institute, Minneapolis (G.B.); the University of Rochester Medical Center, Rochester (J.N.), and Certified Research Associates, Cortland (C.A.S.) - both in New York; Pediatric, Infant, and Adolescent Medicine, Ventura, CA (C.C.); Velocity Clinical Research, West Jordan, UT (B.R.); Ann and Robert H. Lurie Children's Hospital, Chicago (W.J.M.); the University of Kentucky, Lexington (G.F.); the Pennington Biomedical Research Center, Baton Rouge, LA (D.H.); and Moderna, Cambridge, MA (J.E.T., D.D., C.R., B.K., X.Z., W.D., H.Z., D.R.S., K.H., B.G., K.S., R.M., R.P., A.A., R.D., J.M.M., S.S.G.).