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

Abstract

Objective: This 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, 21days) among people who inject drugs (PWID).

Methods: Randomised 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.

Results: Compared 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.

Conclusions: Modest 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.

Keywords: Conditional cash transfers; Contingency management; Hepatitis B; People who inject drugs; Vaccination.