1 From the Clinical and Translational Epidemiology Unit, the Division of Gastroenterology, and the Cancer Center, Massachusetts General Hospital and Harvard Medical School (A.T.C.), the Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health (A.T.C.), the Massachusetts Consortium for Pathogen Readiness (A.T.C., J.S.B.), the Computational Epidemiology Lab, Boston Children's Hospital and Harvard Medical School (J.S.B.), and the Departments of Pediatrics and Biomedical Informatics, Harvard Medical School (J.S.B.) - all in Boston.