1. Epidemic Intelligence Service and Immunization Safety Office, Centers for Disease Control and Prevention, Atlanta, Georgia (E.M.H., J.D.)
2. Kaiser Permanente South Bay Medical Center, Harbor City, California (R.A.N.)
3. Institute for Health Research, Kaiser Permanente Colorado, Denver, Colorado (M.F.D.)
4. Kaiser Permanente, Pasadena, California (D.G., C.Z.)
5. Kaiser Permanente Center for Health Research, Portland, Oregon (M.L.H.)
6. Kaiser Permanente Washington Health Research Institute, Seattle, Washington (L.A.J.)
7. HealthPartners Institute for Education and Research, Minneapolis, Minnesota (J.N.)
8. Marshfield Clinic Research Institute, Center for Clinical Epidemiology and Population Health, Marshfield, Wisconsin (S.C.O.)
9. Kaiser Permanente Vaccine Study Center, Oakland, California (O.Z.)