1. Division of Pediatric Infectious Diseases, Department of Pediatrics, University of Utah, Salt Lake City, Utah;
2. Division of General Pediatrics, Department of Pediatrics, University of California, San Francisco, California;
3. Departments of Pediatrics and Biostatistics and Epidemiology and Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania; and
4. Division of Infectious Diseases and Center for Pediatric Clinical Effectiveness, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania