1. National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia;
2. Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, Georgia;
3. Atlanta Veterans Affairs Medical Center, Atlanta, Georgia;
4. Connecticut Department of Public Health, Hartford, Connecticut;
5. Division of Epidemiolgy, School of Public Health, University of California, Berkley, Berkley, California; and
6. Minnesota Department of Health, St. Paul, Minnesota