Effect of low-threshold methadone maintenance therapy for people who inject drugs on HIV incidence in Vancouver, BC, Canada: an observational cohort study

Background HIV infection in people who inject drugs (PWID) is an international public health concern. We aimed to assess the effect of methadone maintenance therapy on HIV incidence in PWID in Vancouver, BC, Canada, where methadone is widely available through family physicians' offices and dispensed by community pharmacies. Methods Data were derived from the Vancouver Injection Drug Users Study (VIDUS), a prospective cohort of PWID in Vancouver. Individuals were eligible to enrol in VIDUS if they had injected illicit drugs at least once in the previous month and lived in the Greater Vancouver region. Participants responded to an interviewer-administered questionnaire and provided blood samples at enrolment and follow-up visits every 6 months. We estimated time to HIV seroconversion with Kaplan-Meier methods and used Cox proportional hazards methods to assess associations between methadone use and time to seroconversion. Findings 1639 HIV-negative individuals were recruited between May 1, 1996, and May 31, 2013. Of these individuals, 138 had HIV seroconversion during a median of 75.5 months (IQR 33.4-115.3) of follow-up. In multivariate Cox regression analyses, methadone maintenance therapy remained independently associated with a reduced hazard of HIV infection after adjustment for sociodemographic characteristics and drug use patterns (adjusted relative hazard 0.64, 95% CI 0.41-0.98). Interpretation Methadone maintenance therapy for PWID made available through primary care physicians and community pharmacies can help to achieve public health goals such as reducing the spread of HIV.