A Study to Test the Efficacy of the HBV Vaccine and to Look at the Prevalence of HBV Infection

The prevalence of the Hepatitis B core antigen (anti-HBc)in the Thai population is about 70 %. No data of isolated anti-HBc is reported. Anti-HBc antigen is observed in 10%-20% of individuals from low endemic areas of HBV infection. The prevalence of isolated antiHBc antigen is expected to be higher in endemic areas of HBV infection. There is conflicting data of occult HBV infection in HIV-infected patients. In Thailand, perinatal transmission is the main route of HBV transmission, different from developed countries. Therefore, isolated anti-HBc in Thai people has longer duration than low prevalence regions. Moreover, HBV genotype C and B is common in this region. HBV genotype C is correlated with more cirrhosis and hepatoma than genotype B. A study from Taiwan demonstrated that HBV DNA \> 100,000 copies/ml is correlated with cirrhosis and hepatoma. Sustained reduction of HBV replication lowers the risk of hepatoma in HBV related cirrhosis. If the HBV vaccination could eliminate an occult HBV infection in these individuals, the liver related mortality will be reduced. The prevalence and its clinical importance of isolated anti-HBc in the Thai population has not been investigated yet. There is also limited data of HBV vaccine response in this setting.