A randomised controlled trial of financial incentives to increase hepatitis B vaccination completion among people who inject drugs in Australia

•Hepatitis B vaccination completion rates are low among people who inject drugs.•First head-to-head randomised trial of financial incentives for vaccination completion•Those who received financial incentives were more likely to complete.•The strategy may also be useful for other vaccine preventable infections.

ObjectiveThis study aimed to investigate the efficacy of modest financial incentives in increasing completion of an accelerated 3-dose hepatitis B virus (HBV) vaccination schedule (0, 7, 21 days) among people who inject drugs (PWID).MethodsRandomised controlled trial. Participants were randomly allocated to receive $30 Australian Dollars cash following receipt of vaccine doses two and three (‘incentive condition’), or standard care (‘control condition’). Serologically confirmed HBV-susceptible PWID. Two inner-city health services and a field study site in Sydney, Australia. The primary outcome was completion of the vaccination series. Additional assessments included self-reported demographic, drug use and treatment, and risk-taking histories.ResultsCompared to the control condition, significantly more participants in the incentive condition received all three vaccine doses, under intention-to-treat analyses (n = 139; 87% versus 66%; p = .004); and within the specified window periods under per protocol analyses (n = 107 received three vaccine doses; 92% versus 67%; p = .001). Multivariate analysis indicated that the incentive condition and longer injecting histories significantly increased the likelihood of series completion. Aboriginal/Torres Strait Islanders were significantly less likely to complete the series.ConclusionsModest financial incentives, per-dose, increased adherence to the accelerated HBV vaccination schedule among PWID. Results have implications for increasing HBV and, potentially, other vaccine-preventable infections, among PWID.