Rising hepatitis A immunity in U.S. military recruits

Background: The U.S. military immunizes new recruits against hepatitis A. Since 2001, immunization with the hepatitis A vaccine has been recommended for civilian adolescents in higher risk areas. Recently, the Armed Forces Epidemiological Board recommended serologic screening where feasible to reduce redundant recruit immunizations. Objectives: The purpose of this study was to determine hepatitis A seroprevalence in recruit populations to inform screening policy. Methods: Banked serum from a sample of military recruits (n = 2,592) in 2004 was tested for total antibody to hepatitis A (anti-hepatitis A virus (HAV)). Results: The overall anti-HAV seroprevalence was 12.0% (95% confidence interval, 10.8%-13.3%). Adjusted to the age distribution of the 18- to 34-year-old population, the seroprevalence was 11.9% (10.5%-13.4%). The lowest seroprevalence was noted in the 1984 birth cohort, with significantly higher seroprevalence among younger recruits. Conclusions: Rising hepatitis A immunity among successive birth cohorts suggests increasing compliance with immunization recommendations. In anticipation of rising population immunity, universal screening of military recruits for anti-HAV is recommended.