Abstract
BACKGROUND: The epidemiological impact and the duration of protection provided by infant hepatitis B (HB) vaccination are unknown. OBJECTIVES: This study was designed to determine the hepatitis B virus (HBV) infection seromarkers in young adults who have been vaccinated against HBV as the first group of Iranian neonates during 1993 and 1994. PATIENTS AND METHODS: We recruited 510 young adults with a history of complete HB vaccination at birth. HBV seromarkers (HB surface antigen (HBs Ag), antibody against HBs Ag (Anti-HBs), and antibody against HB core antigen (Anti-HBc) were measured using ELISA method. Anti-HBs titers ≥ 10 IU/L were considered protective and titers more than 300 IU/L were indicative of a natural boosting. Positive results for Anti-HBc and HBs Ag were considered as breakthrough infection and possible vaccine failure, respectively. The history of acute symptomatic clinical hepatitis was also investigated. RESULTS: Anti-HBs seropositivity rate was detected in 224 of 510 [95% CI: 39-47] young adults. Breakthrough infection (positive sera for Anti-HBc without chronic infection) was observed in 18 [95% CI: 2.5-3.5] subjects. There were neither HBs Ag positive results nor symptomatic hepatitis cases. CONCLUSIONS: The study results indicated that the neonatal HBV immunization induced a long-term protection against HBV and was very efficacious in reducing chronic HBV infection rate in vaccinated young adults in Iran.