1. From the Department of Pediatrics, Division of Infectious Disease, Boston Medical Center, Boston University School of Medicine, Boston, Massachusetts;
2. Department of Pediatrics, Division of Infectious Diseases, Children's Hospital, Harvard Medical School, Boston, Massachusetts;
3. Health Science Center, Brooklyn and State University of New York, Brooklyn, New York;
4. Department of Pediatrics, University of Illinois, Urbana, Illinois;
5. Department of Pediatrics, Baylor College of Medicine, Houston, Texas;
6. Department of Pediatrics, Columbia-Presbyterian Hospital, New York, New York;
7. Department of Pediatrics, University of Puerto Rico, San Juan, Puerto, Rico;
8. Pediatric Adolescent and Maternal AIDS Branch, National Institute of Child Health and Human Development, Washington, DC; and
9. New England Research Institutes, Watertown, Massachusetts.