Objectives: We described seroprevalence of antibody to hepatitis A virus (anti-HAV) in the United States during 1999-2006 and compared it with seroprevalence before the availability of vaccine.
Methods: We analyzed data from the 1988-1994 and 1999-2006 National Health and Nutrition Examination Survey (NHANES) to obtain estimates of anti-HAV seroprevalence for the U.S. household population. We grouped region of residence based on the 1999 Advisory Committee on Immunization Practices recommendations into 17 states with any recommendation (vaccinating) and 33 states without any recommendation (non-vaccinating).
Results: During 1999-2006, the overall seroprevalence of anti-HAV was 34.9% (95% confidence interval [CI] 33.1, 36.7). During 1999-2006, U.S.-born children living in vaccinating states (33.8%, 95% CI 26.2, 42.2) had a higher seroprevalence than children in non-vaccinating states (11.0%, 95% CI 9.4, 12.8; p < 0.001). Seroprevalence among children increased from 8.0% (95% CI 6.3, 10.1) during 1988-1994 to 20.2% (95% CI 16.0, 24.8) during 1999-2006 (p < 0.001). For U.S.-born children aged 6-19 years, the strongest factor associated with seroprevalence was residence in vaccinating states. Among U.S.-born adults aged > 19 years, the overall age-adjusted seroprevalence of anti-HAV was 29.9% (95% CI 28.3, 31.5) during 1999-2006, which was not significantly different from the seroprevalence during 1988-1994 (32.2%, 95% CI 30.1, 34.4).
Conclusions: Increases in seroprevalence among children in vaccinating states suggest a positive effect of the 1999 vaccination recommendations.