1. From the Departments of Public Health and
2. Biostatistics, School of Public Health, and the
3. Clinical Public Health and
4. Department of Pediatrics and Communicable Disease, School of Medicine, University of Michigan, Ann Arbor, Michigan; the Departments of
5. National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland.
6. Pediatrics, College of Physicians & Surgeons, Columbia University, New York, New York; and the