Cost effectiveness of the Vancouver Supervised Injection Facility

Presenter: Gregory Zaric, University of Western Ontario

Abstract

Background: Insite, a supervised injection facility, has operated in Vancouver, Canada, since 2003. Currently the facility operates under a constitutional exemption from the Controlled Drugs and Substances Act. Previous research has found that the facility is associated with decreased needle sharing, increased use of bleach, and increased referrals into methadone treatment. We sought to determine the cost effectiveness of the facility.

Methods: We developed a dynamic compartmental model of the population of downtown Vancouver. The population was divided into 12 compartments representing all combinations of 4 infection categories (HIV-infected, Hepatitis C infected, co-infected with HIV and Hepatitis C, and not infected), and 3 behavior categories (injection drug user, injection drug user enrolled in methadone treatment, and not an injection drug user). A system of nonlinear differential equations was constructed to describe the movement of individuals between model compartments. We parameterized the model using data specific to Vancouver where possible, and from secondary sources otherwise. We simulated for 10 years to estimate the incremental costs and health impact of the facility. Costs and health benefits were discounted at 5% annually.

Results: In the base case we consider decreased needle sharing as the only benefit of the facility. This case resulted in 920 life years of survival gained and a net savings of $14 million. Incorporating increased use of bleach and increased referrals into methadone treatment resulted in greater health benefits and cost savings. We conducted extensive sensitivity analysis. The incremental cost effectiveness ratio exceeded $50,000 per life year gained if the average annual number of injections per injection drug user was less than 284; if the rate of needle sharing was less than 5.1%; or if the annual operating cost of the facility exceeded $10.3 million.

Conclusions: The Vancouver supervised injection facility is associated with improved health and cost savings, even under conservative assumptions. The cost savings are due largely to savings from HIV cases averted. The facility was either cost saving or had an incremental cost effectiveness ratio of less than $50,000 per life year gained under a wide range of scenarios.