Hepatitis B virus infection in children: epidemiology, natural course and prevention in Taiwan

Although most hepatitis B virus (HBV) related chronic liver diseases manifest themselves in adulthood, HBV infection usually begins in infancy or early childhood in hyperendemic areas. The following factors affect the natural course of HBV: 1) host factors: a) initial age of infection: the younger the patient at infection, the more chance the disease will run a chronic course. Immune tolerance to hepatitis B e antigen (HBeAg) and core antigen persists for a period of time in young children. b) the immune status of the host: the usage and tapering of immunosuppressants may induce a severe course with a fatal outcome; 2) maternal carrier status: children of HBeAg seropositive mothers are more immune tolerant to HBV, and thus have lower rates of HBeAg and hepatitis B surface antigen (HBsAg) seroconversion; and 3) viral factors: mutations of the HBV precore, core or core promoter genes are related to fulminant hepatitis B or severe chronic hepatitis B. However, this is a matter of contention. Since July 1984, a nationwide HBV vaccination program has been successfully conducted in Taiwan. In 1994, the HBsAg carrier rate in Taipei city was reduced to < 1% in children younger than 10 years of age. Continuous efforts in immunoprophylaxis will hopefully further reduce the incidence of hepatitis and hepatocellular carcinoma in the next generation.