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Vaccine Wkly. 1995 May 22:8-9.

Long-term vaccination decreasing HBV in the Gambia.

[No authors listed]



In Sub-Saharan Africa, where hepatitis B virus (HBV) is endemic, children are often chronic carriers of HBV, and sibling-to-sibling transmission is common. HBV often leads to hepatocellular carcinoma, chronic hepatitis, and cirrhosis. In The Gambia, vaccination against HBV in infancy has been used since 1986 and continues to be used to reduce chronic carriage of HBV and to reduce the incidence of hepatocellular carcinoma, chronic hepatitis, and cirrhosis. Pilot studies of HBV immunization were conducted in Keneba and Manduar villages, where there has been a well-documented HBV infection pattern. HBV antibody levels fell rapidly. Vaccine efficacy against HBV infection and chronic carriage of hepatitis B s antigen (HBsAg) levels has risen. In 1993, it was 94.7% and 95.3%, respectively. The prevalence of infectivity markers (HBeAg and HBV DNA) has fallen with age. During the second 4-year period, there were more than 50% fewer breakthrough infections than expected. The infectivity of current chronic carriers and HBV transmission will diminish should the Gambian HBV vaccination program continue. In fact, the vaccine will become more effective regardless of low antibody levels. Future programs in very endemic countries where the chief mode of HBV transmission is horizontal should initially vaccinate all children less than 5 years old to prevent acute infections in older siblings. This, in turn, will strengthen vaccine efficacy in infants.

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