Persistence of antibodies to the surface antigen of the hepatitis B virus (anti-HBs) in children subjected to the Expanded Programme on Immunization (EPI), including hepatitis-B vaccine, in Thailand

Will hepatitis-B vaccine administered at birth, and at 2 and 6 months of ag e, as an integral part of Thailand's Expanded Programme on Immunization, pr ovide long-term protection? In an attempt to answer this question, resident s of five provinces (representing five distinct geographical areas of Thail and) who were aged 1-10 years and had received this course of vaccination w ere enrolled on a serological study. Each was tested, with ELISA, for the s urface antigen of hepatitis B (HBsAg) and for antibodies against this antig en (anti-HBs) or against the core antigen (anti-HBc). Over all age-groups, the prevalences of HBsAg, anti-HBs and anti-HBc were 0.67%, 71.4% and 5.5%, respectively. Although the prevalence of anti-HBs decreased with age, it r emained at 56%-65% among those aged 6-10 years. Between 2% and 17% of the s ubjects aged 1-9 years had high titres of anti-HBs. Based on these results, an additional booster, still a controversial issue, does not appear to be required in order to prevent infection with hepatitis B virus and thus perm it the eventual eradication of chronic carriage and its fatal sequelae in T hailand.