Supervised injection sites offer a safe and hygienic environment for people to inject their previously obtained illicit drugs under supervision.1,2 Observational studies from the facility in Vancouver, British Columbia, have demonstrated positive effects: a decrease in needle sharing and reuse of syringes, fewer people injecting drugs in public, an increase in referrals to social services and addiction counselling, a decrease in the number of publicly discarded syringes, no apparent increase in police reports of drug dealing or crime, and no observed increase in new initiates into drug use. [3][4][5] Although an expert advisory committee recently concluded that the Vancouver facility has beneficial effects, prominent law enforcement groups have argued that the resources allocated to the facility would be more effectively spent elsewhere. 6,7 We used computer simulation to estimate the projected impact of Vancouver's supervised injection site on survival, rates of HIV and hepatitis C virus infection, referral to methadone maintenance treatment and associated costs. Our goal was to assess the cost-effectiveness of the facility and thus provide important insights into this policy debate.
Methods
Simulation modelWe developed a dynamic compartmental model to simulate the population of Vancouver, British Columbia. The population included injection drug users, non-users, persons with HIV and hepatitis C virus infection, and those with combinations of these states. Our model categorized populations into discrete compartments. By defining the probabilities of moving between compartments, we were able to project the prevalence of each model state throughout the time horizon of the simulation. Tracking the time spent in each state allowed us to estimate survival. Assigning a cost to each state allowed us to estimate net costs of treatment. The perspective of the model was that of a health care system. Accordingly, we included direct medical costs but did not include indirect medical costs or other societal costs. We used a time horizon of 10 years and updated the proportion in each model state every 0.1 years. We used a discount rate of 5% for both costs and life expectancy.