MH Chang

Hepatitis B virus (HBV) infection in children is common in hyperendemic areas. It can cause fulminant hepatitis, acute hepatitis, chronic hepatitis, liver cirrhosis and hepatocellular carcinoma. Although most chronic liver diseases manifest during adulthood, the HBV infection usually begins early in childhood. Patients with a young age at infection, immunecompromised hosts and infants of HBeAg carrier mothers, once infected by HBV, are prone to run a chronic course. Around 90% of the infants of HBeAg-seropositive HBsAg carrier mothers become chronic HBsAg carriers. In contrast infants of HBeAg-seronegative HBsAg carrier mothers are mostly uninfected or recover from HBV infection. Occasionally, they develop acute or fulminant hepatitis. During the initial phase of HBV infection, children are usually asymptomatic and grow well. Aminotransferases are usually within normal limits or mildly elevated. During the phase of HBeAg seroconversion, every enzyme elevation becomes more prominent. Before age 3 years, HBeAg seroconversion is uncommon, the annual HBe seroclearance rate is 2%. After 3 years, the annual HBe seroclearance rate increases to around 3-5%. Active liver histology prior to or just after HBe seroconversion is common. Liver histology gradually becomes inactive after HBe seroconversion. Liver damage can be very serious during the process of HBe seroconversion, even when HBeAg was seroconverted before 3 years of age. Immunoprophylaxis is the best way to prevent hepatitis B virus infection and its related diseases. A mass vaccination programme has been implemented in Taiwan since July 1984. HBV vaccine, 3-4 doses, have been given to all the neonates and hepatitis B immunoglobulin to infants HBeAg-seropositive mothers. This has been extended to preschool and school children and adults. The HBsAg carrier rate has been successfully reduced from 10% in 1984 to less than 1% in Taipei city in 1994 in children 1-8 years of age.