Hepatitis B in the Northern Territory: insights into the changing epidemiology of an ancient condition

Abstract

Background Aboriginal and Torres Strait Islander people are disproportionately affected by hepatitis B virus (HBV) infection. A proposed mismatch between standard vaccines and the HBV/C4 sub‐genotype prevalent in Aboriginal people in the Northern Territory (NT) may reduce vaccine effectiveness. Aims To determine HBV prevalence in the NT by Indigenous status and to explore patterns of immunity following implementation of universal vaccination, using a large longitudinal diagnostic dataset. Methods A retrospective analysis of all available HBV serology results in the NT from 1991 to 2011 was conducted, with HBV prevalence and vaccination status analysed according to adigenous status, age and sex using individuals' patterns of HBsAg, anti‐HBs and anti‐HBc serology over repeated tests. Results 100 790 individuals were tested (33.4% Indigenous) between 1991 and 2011 (26.1% of the 2011 NT population), with a total of 211 802 tests performed. In 2011, the proportion of HBV positive individuals in the NT was 3.17% (5.22% in Indigenous populations) compared to previous 2011 estimates of 1.70% (3.70% in Indigenous populations). The vaccine failure rate was lower than expected with only one presumed vaccinated person subsequently developing HBsAg positivity (0.02%). Evidence of suboptimal vaccine efficacy by breakthrough anti‐HBc positivity in vaccinated individuals was demonstrated in 3.1% of the vaccinated cohort, of which 86.4% identified as Indigenous (HR 1.17). No difference in HBeAg positivity or seroconversion was observed between Indigenous and non‐Indigenous individuals living with CHB. Conclusions The burden of CHB in Indigenous people in the NT has previously been underestimated. A higher HBV prevalence in the NT than described in previous cross‐sectional studies was found, including a higher prevalence in Indigenous people. Evidence of suboptimal vaccine efficacy was demonstrated predominantly in Indigenous individuals.

The forgotten people: Hepatitis B virus (HBV) infection as a priority for the inclusion health agenda

“…Indigenous populations, a global term referring to people with historical ties to a land prior to colonisation, are disproportionately affected by HBV ( Osiowy et al, 2013 ; Russell et al, 2019 ; Howell et al, 2019 ). For example, Aboriginal Australians have a higher HBV prevalence, higher rate of liver disease, and poorer outcomes, compared to non-Indigenous Australians ( Plackett, 2022 ; Qama et al, 2021 ; Wigg et al, 2021 ). A variety of factors may account for this disparity, including reduced healthcare access due to remote location, social inequalities and multi-morbidity ( Plackett, 2022 ; Einsiedel et al, 2013 ).…”

“…HBV genotype may also be an important consideration; genotype C4 in Aboriginal Australians is associated with aggressive disease progression, however this impact is yet to be unpicked from the effects of social determinants of health ( Davies et al, 2019 ; Plackett, 2022 ). In addition, there is some evidence that current HBV vaccine, which is designed against genotype A, may have reduced efficacy against C4 ( Qama et al, 2021 ). Although culturally and geographically distinct, indigenous populations across the globe face an increased burden and worse outcomes from HBV, and are poorly represented by existing data.…”

The Global Impact of Hepatitis B Vaccination on Hepatocellular Carcinoma

“…Low endemicity countries Australia and New Zealand report high rates of infant vaccination coverage (95% and 92% coverage respectively) [ 53 ]. However, there are communities within these countries with higher than background hepatitis B prevalence, such as First Nations Peoples [ 56 , 57 ]. The presence of these high-prevalence groups in low endemicity countries emphasizes the importance of maintaining high rates of vaccination coverage.…”

“Putting the power back into community”: A mixed methods evaluation of a chronic hepatitis B training course for the Aboriginal health workforce of Australia’s Northern Territory

“…The Northern Territory (NT) has the highest prevalence of CHB in Australia (1.84% in comparison to 0.86% nationally) [ 3 ]. Australia’s First Nations people, respectfully referred to as Aboriginal and Torres Strait Islander people, experience a CHB prevalence 2 to 6 times higher than non-Indigenous people [ 4 , 5 ], representing approximately 70% of those affected in the NT [ 6 ]. It is estimated that of those living with CHB, 25% (15–40%) will die from liver disease, namely hepatocellular carcinoma (HCC) ‐ primary liver cancer, and cirrhosis [ 7 , 8 ] without appropriate care.…”