1. Center for Communicable Disease Dynamics, Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, Massachusetts
2. Department of Biostatistics, Harvard T.H. Chan School of Public Health, Boston, Massachusetts
3. Department of Population Medicine, Harvard Pilgrim Health Care Institute and Harvard Medical School, Boston, Massachusetts
4. Department of Epidemiology and Biostatistics, College of Public Health, University of Georgia, Athens, Georgia
5. Center for the Ecology of Infectious Diseases, University of Georgia, Athens, Georgia
6. Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, Massachusetts