Immunogenicity achieved by the intradermal hepatitis B vaccination programme for US Army soldiers in Korea

Hepatitis B virus (HBV) infections are a significant threat to the 30 000 US Army soldiers stationed in South Korea. Hepatitis B surface antigen carrier rates in some Korean populations may run as high as 15%, and HBV incidence estimates for US soldiers in Korea have ranged from 0.6 to 6% per year. In response to this threat, on 1 October 1986 the US Army instituted a mandatory three-dose (0, 30-60, and 60+ days), 0.1 ml per dose, intradermal (i.d.) immunization regimen for all soldiers bound for permanent assignments in Korea. Although shown to be immunogenic in experimental studies, the i.d. route had never been attempted on as large a scale as in this operational setting. During September 1987, an evaluation of programme compliance and immune response was conducted. For those who received three doses according to schedule, antibody response was similar to that reported by previous controlled trials that used the i.d. approach. The three-dose i.d. series appeared to provide protective antibody levels in at least 67% of soldiers, but, consistent with previous trials, antibody levels were approximately one-half those obtained following intramuscular vaccination. We conclude that, as a cost-reduction strategy, wide-scale use of intradermal hepatitis B vaccine may be useful in situations characterized by short-term increased HBV infection risk.