Unsafe injection practices in a cohort of injection drug users in Vancouver: could safer injecting rooms help?

BACKGROUND: In several European countries safer injecting rooms have reduced the public disorder and health-related problems of injection drug use. We explored factors associated with needle-sharing practices that could potentially be alleviated by the availability of safer injecting rooms in Canada. METHODS: The Vancouver Injection Drug User Study is a prospective cohort study of injection drug users (IDUs) that began in 1996. The analyses reported here were restricted to the 776 participants who reported actively injecting drugs in the 6 months before the most recent follow-up visit, during the period January 1999 to October 2000. Needle sharing was defined as either borrowing or lending a used needle in the 6-month period before the interview. RESULTS: Overall, 214 (27.6%) of the participants reported sharing needles during the 6 months before follow-up; 106 (13.7%) injected drugs in public, and 581 (74.9%) reported injecting alone at least once. Variables independently associated with needle sharing in a multivariate analysis included difficulty getting sterile needles (adjusted odds ratio [OR] 2.7, 95% confidence interval [CI] 1.8-4.1), requiring help to inject drugs (adjusted OR 2.0, 95% CI 1.4-2.8), needle reuse (adjusted OR 1.8, 95% CI 1.3-2.6), frequent cocaine injection (adjusted OR 1.6, 95% CI 1.1-2.3) and frequent heroin injection (adjusted OR 1.5, 95% CI 1.04-2.1). Conversely, HIV-positive participants were less likely to share needles (adjusted OR 0.5, 95% CI 0.4-0.8), although 20.2% of the HIV-positive IDUs still reported sharing needles. INTERPRETATION: Despite the availability of a large needle-exchange program and targeted law enforcement efforts in Vancouver, needle sharing remains an alarmingly common practice in our cohort. We identified a number of risk behaviours--difficulty getting sterile needles, needle sharing and reuse, injection of drugs in public and injecting alone (one of the main contributing causes of overdose)--that may be alleviated by the establishment of supervised safer injecting rooms. (Review' s abstract)