1. From Regeneron Pharmaceuticals, Tarrytown, NY (M.P.O., E.F.-N., B.J.M., F.I., K.-C.C., N. Sarkar, P.H., I.H., J.D.D., K.C.T., D.R., A.M., A.T.H., J.D.H., Y.K., L.A.P., A.B., C.A.K., B.K., A.T.D., N. Stahl, L.L., N.B., G.H., G.D.Y., D.M.W.); the Departments of Medicine and Microbiology, University of Pennsylvania, Philadelphia (K.J.B.); the Departments of Global Health and Epidemiology and the Division of Allergy and Infectious Diseases, University of Washington, and the Vaccine and Infectious Diseases...