1. From the *Department of Maternal and Child Health, Harvard School of Public Health, Boston, Massachusetts;
2. Center for Biostatistics in AIDS Research, Harvard School of Public Health, Boston, Massachusetts;
3. Pediatric, Adolescent and Maternal AIDS Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland; and the
4. Efficacy Trials Branch, Division of AIDS, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, Maryland;
5. Department of Pediatrics, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark, New Jersey.