Hepatitis B virus infection was very commonly acquired by Gambian infants before vaccination became widely used in The Gambia. The first group of children to receive the vaccine were part of an MRC study in Keneba-Manduar 20 years ago, and follow-up of this cohort continues.
Between 1986 and 1990 the phased introduction of Hepatitis B (HB) virus vaccination to all Gambian children as part of the Extended Programme of Immunisation allowed the recruitment of two groups of 60,000 children who either received or did not receive HB vaccine at birth, under the auspices of the Gambia Hepatitis Intervention Study (GHIS). This constituted the first phase of an experiment to evaluate the role of HB vaccination in the prevention of liver cancer (the commonest cancer in the Gambia) in adult life. The second phase of the study demonstrated that, despite the waning of antibody levels, protective efficacy of the vaccine was 84% against infection and 94% against chronic carriage. The GHIS is now in the final phase of the study which, through the National Cancer Registry, is looking at the relationship between vaccination and end-stage liver disease, primarily cirrhosis and hepatoma. We have recently completed a study to examine the benefits of booster vaccination of adolescents who were first immunised at birth. In addition, we are studying factors that influence the development of cirrhosis and hepatoma in people with chronic Hepatitis B virus carriage, including host genetic factors, the development of viral mutants and environmental exposure to factors such as aflatoxin.
