Long‐Term Benefit of Hepatitis B Vaccination among Children in Thailand with Transient Hepatitis B Virus Infection Who Were Born to Hepatitis B Surface Antigen–Positive Mothers

BACKGROUND: Transmission of hepatitis B virus (HBV) from carrier mothers to their babies appears to be one of the most important factors influencing the prevalence of chronic HBV infection in areas of high hepatitis B endemicity. METHODS: Infants born to HBV surface antigen (HBsAg)-positive mothers who were or were not positive for HBV e antigen (HBeAg) or to mothers who were negative for both HBsAg and HBeAg have been followed for 17 years for serological evidence of HBV infection. These infants were divided into 2 groups on the basis of their hepatitis B vaccination protocols: group 1 received vaccine at birth and 1, 2, and 12 months later, and group 2 received vaccine at birth and 1 and 6 months later. Follow-up involved annual clinic visits, during which a blood sample was taken and analyzed for the presence of HBsAg, antibody to HBsAg, and antibody to HBV core antigen (HBcAg). Selected blood samples that tested positive for HBV markers during 2 consecutive visits separated by a long interval were further investigated by polymerase chain reaction to detect HBV DNA. RESULTS: Transient presence of HBsAg or transient and/or long-term presence of antibody to HBcAg suggested that this population was heavily exposed to HBV during the follow-up period. Despite these findings, no new cases of chronic HBV infection were observed. None of the subjects with transient presence of HBsAg had any clinical symptoms of liver disease. CONCLUSIONS: This study demonstrates the efficacy of the HBV vaccine and its ability to protect against symptomatic disease.