1. Department of Research & Evaluation, Kaiser Permanente Southern California, Pasadena
2. Department of Health Systems Science, Kaiser Permanente Bernard J. Tyson School of Medicine, Pasadena, California
3. Centers for Disease Control and Prevention, Epidemic Intelligence Service, Atlanta, Georgia
4. Denver Health, Office of Research Ambulatory Care Services, Denver, Colorado
5. HealthPartners Institute, Bloomington
6. Kaiser Permanente Colorado, Institute for Health Research, Denver, Colorado
7. Kaiser Permanente Washington Health Research Institute, Seattle
8. Marshfield Clinic Research Institute, Marshfield, Wisconsin
9. Department of Research, Kaiser Permanente Northern California, Oakland
10. Kaiser Permanente Northwest, Center for Health Research, Portland, Oregon
11. Harvard Pilgrim Health Care Institute, Boston, Massachusetts
12. Centers for Disease Control and Prevention, Immunization Safety Office, Atlanta, Georgia
13. Division of Viral Diseases, Respiratory Viruses Branch, Centers for Disease Control and Prevention, Atlanta, Georgia