1. Centers for Disease Control and Prevention, Atlanta, Georgia;
2. Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia;
3. HealthPartners Institute for Education and Research, Minneapolis, Minnesota;
4. Kaiser Permanente of Northern California, Oakland, California;
5. Kaiser Permanente Northwest, Portland, Oregon;
6. Marshfield Clinic Research Foundation, Marshfield, Wisconsin;
7. Institute for Health Research, Kaiser Permanente Colorado, Denver, Colorado; and
8. Kaiser Permanente Southern California, Pasadena, California