Incident hepatitis B virus infection and immunisation uptake in Australian prison inmates

Despite an effective vaccine, hepatitis B virus (HBV) infection continues to impose a large burden of disease globally. Until childhood immunisation achieves high adult population coverage, people who inject drugs (PWID), including prison inmates remain at risk. PWID have a higher prevalence of HBV than the wider population, and lower rates of vaccine-conferred immunity. This study sought to identify the incidence and predictors of HBV transmission and uptake of immunisation in PWID prisoners in Australia.

Longitudinally collected, stored sera from subjects previously enrolled in a prospective study of hepatitis C in recently incarcerated PWID prisoners (n = 590) were serologically tested for HBV. Interviews recording demographic and behavioural risks were analysed. Multivariate statistical analyses were applied to identify associations of incident infection or immunisation.

Upon imprisonment there were n = 373 (63%) individuals who were HBV susceptible, of whom 140 remained susceptible at the subsequent enrolment into the cohort, and had one or more follow-up visits (a total of 406.73 person years [p.y.]), and so were included in this analysis. There were 7 incident cases of HBV infection (1.7 per 100 p.y.) in this group, with transmission being associated with injecting drug use daily or more often. There were 48 individuals who were successfully immunised (11.8 per 100 p.y.) with younger age and continuous imprisonment predicting this outcome.

The Australian prison environment poses a high risk for HBV infection, and also provides an opportunity for immunisation for PWID. Further efforts are required to improve coverage and prevent ongoing transmissions.