Journal of Medical Virology 70:S111–S118 (2003) Varicella in Americans From NHANES III: Implications for Control Through Routine Immunization Paul E. Kilgore, 1,2 * Deanna Kruszon-Moran, 6 Jane F. Seward, 2 Aisha Jumaan, 2 Frederik P.L. Van Loon, 4 Bagher Forghani, 7 Geraldine M. McQuillan, 6 Melinda Wharton, 2 Laura J. Fehrs, 5 Cynthia K. Cossen, 7 and Stephen C. Hadler 3 1 International Vaccine Institute, Seoul, Korea 2 Epidemiology and Surveillance Division, National Immunization Program, Centers for Disease Control and Prevention, Atlanta, Georgia 3 Global Immunization Division, National Immunization Program, Centers for Disease Control and Prevention, Atlanta, Georgia 4 Immunization Services Division, National Immunization Program, Centers for Disease Control and Prevention, Atlanta, Georgia 5 Epidemiology Program Office, Centers for Disease Control and Prevention, Atlanta, Georgia 6 National Center for Health Statistics, Centers for Disease Control and Prevention, Hyattsville, Maryland 7 Viral and Rickettsial Diseases Laboratory, California State Department of Health Services, Richmond, California At the time of varicella vaccine introduction in the United States, an estimated 4 million episodes of varicella occurred annually. This survey of varicella seroprevalence is the first to describe immunity to a vaccine-preventable disease prior to vaccine introduction in the United States population. The objective of this analysis is to describe patterns of naturally-acquired varicella and understand characteristics associated with infection in the varicella vaccine–naive United States population. A nationally representative cross-sectional health examination survey that included venipuncture was conducted among 21,288 U.S. participants aged 6 years and older from 1988 through 1994. Serologic evidence of varicella-zoster virus infection was measured by enzyme immunoassay of varicella-zoster virus- specific IgG antibody. The seroprevalence of IgG antibody to varicella-zoster virus increased from 86.0% in children aged 6 through 11 years to 99.6% in adults aged 40 through 49 years. Immunity to varicella remained at 99% or higher in Americans aged 50 years and older. Among persons aged 6 through 19 years, non-Hispanic black children were 40% less likely to be sero- positive compared with white children (odds ratio [OR], 0.6; 95% confidence interval [CI], 0.4–0.8). Among young adults aged 20 through 39 years, women with a history of live birth (OR, 4.3; 95% CI, 2.1–8.7) and married men (OR, 2.7; 95% CI, 1.2–5.7) were more likely to have naturally- acquired immunity to varicella. This study found that, prior to use of varicella vaccine in the United States, age, race, and marital char- acteristics were independently associated with naturally acquired varicella. Future varicella serosurveys in Americans will provide essential information to interpret the population impact of varicella vaccine. J. Med. Virol. 70:S111– S118, 2003. ß 2003 Wiley-Liss, Inc. KEY WORDS: chickenpox; chickenpox vaccine; health surveys; herpesvirus 3, human; immunoenzyme techni- ques; immunologic surveil- lance; population surveillance; seroepidemiologic stud-ies; sur- veillance; vaccination; viral vac- cines; virus diseases; United States Presented in part as (Abstract H-112, Session no. 155-H), p. 233, 37th Interscience Conference on Antimicrobial Agents and Chemotherapy, Toronto, Canada, September 29, 1997. Informed consent was obtained from participants and human experimentation guidelines of the U.S. Department of Health and Human Services were followed in the conduct of this investigation. Frederik P.L. Van Loon’s present address is Centrum De Nieuwe Vaart, Hilversum 1217SP, The Netherlands. *Correspondence to: Paul E. Kilgore, M.P.H., M.D., Interna- tional Vaccine Institute, Kwanak P.O. Box 14, Seoul, Republic of Korea. E-mail: pkilgore@ivi.int Accepted 13 September 2001 DOI 10.1002/jmv.10364 Published online in Wiley InterScience (www.interscience.wiley.com) ß 2003 WILEY-LISS, INC.