Estimates Of Chronic Hepatitis B Virus Infection In The Northern Territory

(30.1-51.2%), HBcAb 28 per cent (16.4-39.3%), and HBsAg 0.8 per cent (0-1.7%). These are the fi rst esti- mates of HBV prevalence since the introduction of universal HBV immunisation in the Northern Territory in 1990. The signifi cantly (0.005) higher prevalence of HBsAb in 1-4-year-olds, compared with the nat- ional serosurvey (Table 2) refl ects the impact of the Northern Territory immunisation program (a national infant program commenced in 2000, after these sera were collected). The estimated rate of chronic HBV infection in the Northern Territory (0.8%) was similar to that in the nat- ional serosurvey. Although the status of subjects whose sera were collected is not known, it was estimated that approximately 50 per cent would be Indigenous peo- ple (personal communication, Dr Gary Lum, Director, Northern Territory Government Pathology Service). Compared with the national serosurvey, there was a higher proportion with evidence of past infection (HBcAb positive) at all ages (Table 2). This was partic- ularly noticeable for children aged under nine years, in whom the proportions were more than 15 times higher in the Northern Territory than nationally, even though hepatitis B infections in this age group are preventable by current vaccination programs. Although the number of sera tested was small and individual clinical data are not available, the prevalence in a random sample of Northern Territory Indigenous children, including those from remote regions, would be likely to be higher. More specifi c studies are needed to examine the impact of the hepatitis B immunisation program in the Northern Territory in more detail.