CONTINGENCY MANAGEMENT IMPROVES COMPLETION OF HEPATITIS B VACCINATION IN THOSE ON TREATMENT FOR OPIATE DEPENDENCE: AN ECONOMIC EVALUATION

Purpose:  Contingency management has been proposed as a public health approach to improve patient adherence for hepatitis B virus (HBV) vaccination in people who inject drugs (PWID) entering community treatment by using financial incentives to encourage attendance. The purpose of this study is to determine whether the provision of financial incentives to improve HBV vaccine completion in PWID in England and Wales represents a cost-effective use of NHS resources.

Method(s):  A probabilistic cost effectiveness analysis was conducted based on results from a UK cluster randomised trial and uses a decision-tree to estimate the short-term clinical and cost impact of the vaccination strategies followed by a Markov process to evaluate the long-term clinical consequences and costs associated with HBV infection. Attendance and costs associated with the vaccination strategies were taken directly from the trial. Published sources were used for parameters related to the long-term clinical, quality of life and cost consequences of HBV-related infection. The incidence of HBV was estimated from cross-sectional survey data.

Result(s):  We find that contingency management using financial incentives to improve completion of hepatitis B vaccination in people injecting drugs entering community-based services is likely to be cost-effective under current willingness to pay. This study has a number of strengths and uses data from a well-conducted cluster randomised controlled trial of contingency management versus treatment as usual in twelve specialist NHS services providing opiate substitution treatment in England.

This study highlighted a number of challenges when modelling the effect of vaccination uptake in PWID including estimating the incidence of HBV in the UK, estimating the probability for PWID to be reached in the future by current targeted vaccination programs, estimating the duration PWID remain at increased risk of HBV infection and the risk of HBV after ceasing injection.

Conclusion(s): Results from this study suggest that using contingency management to increase vaccination uptake using financial incentives in injecting problem drug users should be seriously considered as a worthwhile additional investment to improve health outcomes. The generalizability of our results requires careful consideration, but results indicated that contingency management remained worthwhile even when the incidence of HBV was low in this population.