RESUMO
Hepatitis B virus infection and associated diseases are a major public health problem. This study was planned to find out the persistence of antibody against hepatitis B surface antigen in Iranian vaccinated children after five years. Anti-HBs titers in a group of healthy good - responder children who were vaccinated with Cuban hepatitis B vaccine in infancy were measured after five years. Children with antibody titers <100mlU/mI were revaccinated and retested after four weeks. Mean anti-HBs titers in 68 children [29 females, 39 males] were 482.1mIU/mL at six months after the third dose of primary vaccination and 153mIU/mL at five years later. Total mean anti-HBs titers in 36 [52.9%] children out of 68 [17 females, 19 males] were 38.3mIU/ml and 4 [5.8%] of 68 children [two of each sexes] had no detectable antibody after five years. Total mean anti-HBs titers in these hypo- responder and non- responder were 774.3mIU/mL and 625.5mIU/mL respectively after booster dose. In a group of children, who were immunized with Cuban hepatitis B vaccine from birth, anti-HBS titers fell at 6.5 years of age and almost half of children became hypo responder or no responder and their anti-HBs titers developed secondary rise after booster vaccination. All children showed immunologic memory to a booster dose