Hepatitis B virus immunity in Indigenous and "at risk" children who received hepatitis B vaccination in infancy

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Hepatitis B virus (HBV) is transmitted by blood exposure or sexual contact and infection can result in chronic liver disease and liver cancer. Since 2000 Hepatitis B virus immunisation has been recommended for all infants in Australia with the first dose given at birth. However, prior to routine universal immunisation, a selective immunisation strategy was used in Australia from 1986. This targeted infants considered at high risk of HBV infection because of high prevalence in their population of origin, (including Aboriginal- Torres Strait Islanders) and infants whose mother was a HBV carrier. These children, among the first to be vaccinated, are now adolescents. There have been no long-term follow-up studies in Australia, and limited studies elsewhere, to assess the extent of breakthrough infection and persistence of immunity to Hepatitis B after vaccine at birth. As onset of sexual activity is associated with an increased exposure to hepatitis B infection, booster doses may be needed, especially in high-risk individuals. This study includes 2 high risk groups - young indigenous adults in the Northern Territory and young adults born to HBV carrier mothers in central Sydney. It will measure the number of children who have been infected with HBV or are chronic carriers, compared to pre immunisation data, and also the persisting level of immunity in children who were vaccinated against HBV as an infant. Children whose blood test indicates that they have low immunity will be given a booster dose of HBV vaccine and their immune response measured. A rise in hepatitis B antibody following booster vaccination indicates that you have immunological memory and is currently considered to show protection from natural hepatitis B infection. If clinically significant HBV infections are found to be rare and immunologic memory can be demonstrated, this would provide good evidence to support the argument that booster vaccine doses are not required in the Australian context.