1. Department of Pediatrics, University of Colorado at Denver and Health Sciences Center, Denver, Colorado, , Children's Outcomes Research Program, The Children's Hospital, Denver, Colorado
2. Department of Preventive Medicine and Biometrics, University of Colorado at Denver and Health Sciences Center, Denver, Colorado, Children's Outcomes Research Program, The Children's Hospital, Denver, Colorado
3. Department of Colorado Health Outcomes Program, University of Colorado at Denver and Health Sciences Center, Denver, Colorado, Children's Outcomes Research Program, The Children's Hospital, Denver, Colorado
4. Department of Colorado Health Outcomes Program, University of Colorado at Denver and Health Sciences Center, Denver, Colorado
5. Children's Outcomes Research Program, The Children's Hospital, Denver, Colorado
6. National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia
7. Department of Pediatrics, University of Colorado at Denver and Health Sciences Center, Denver, Colorado, Children's Outcomes Research Program, The Children's Hospital, Denver, Colorado