Hepatitis B reservoirs and attack rates in an Australian community. A basis for vaccination and crossinfection policies.

Four different subpopulations in South Australia, which were expected to have high rates of hepatitis B infection (Asians, Aboriginals, homosexual men, and drug addicts) were examined for their contribution to the total reservoir of hepatitis B surface antigen (HBsAg) carriers and to the total annual incidence of acute hepatitis B infection in South Australia. Age-specific prevalence data were also examined to assess the ages at which infection is commonly acquired. It was found that the above four groups, which comprise 3% of the State's population, are likely to include about 75% of HBsAg carriers in the State, but contribute a minority of the total new infections each year; they are not likely to present a significant risk of infection to the community at large. Three different age-related patterns of acquisition of infection were recognized--among Southeast Asians and Aboriginals, homosexual men and drug addicts, and the general community, respectively. The above approach, and to some extent the general findings, should be applicable to other similar communities in the formulation of effective policies for the control and prevention of hepatitis B infection.