*Maternal and Pediatric Infectious Disease Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD; †Fred Hutchinson Cancer Research Center, Seattle, WA; ‡Department of Pediatrics, Stanford University School of Medicine, Palo Alto, CA; §University of Zimbabwe College of Medicine, Harare, Zimbabwe; ‖Centre for the AIDS Programme of Research in South Africa (CAPRISA), Nelson R Mandela School of Medicine, University of KwaZulu Natal, Durban, South Africa; ¶Makerere University-Johns Hopkins University Research Collaboration, Kampala, Uganda; #Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania; **Harvard School of Public Health, Boston, MA; ††Family Health International, Research Triangle Park, Chapel Hill, NC; ‡‡Johns Hopkins Medical Institutes, Baltimore, MD; §§National Institute of Allergy and Infectious Diseases, NIH, Bethesda, MD; ‖‖Maternal Adolescent and Child Health, University of the Witwatersrand, Johannesburg, South Africa, and ¶¶Statistical Center for HIV/AIDS Research and Prevention (SCHARP), Seattle, WA.