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Needle Exchange Reduces HIV Transmission

Montreal injection drug users who always acquired syringes from needle exchanges or other safe sources had a significantly lower likelihood of becoming infected with HIV.

Sharing used syringes and other equipment for drug injection is one of the most efficient means of transmitting HIV, hepatitis B or C, and other blood-borne pathogens. In an attempt to reduce infection rates, numerous cities have established programs to distribute clean needles to injection drug users (IDUs).

As reported in the May 1, 2011, American Journal of Epidemiology, Julie Bruneau from the University of Montreal and colleagues examined trends in HIV incidence, evaluated changes in risk behavior, and assessed associations between syringe access programs and HIV seroconversion among local IDUs.

Montreal was among the first North America cities to adopt harm-reduction strategies such as needle exchange in the 1990s. However, a 1995 study showed that HIV incidence was actually higher among IDUs who used the exchanges -- an unexpected finding. The Montreal Public Health Department subsequently made changes to the programs, including doubling the number of syringes available.

This prospective analysis included 2137 IDUs in Montreal who were HIV negative at the time of enrollment between 1992 and 2008.


  • A total of 148 IDUs became HIV positive within 4 years after enrollment, for an overall incidence rate of 3.3 cases per 100 person-years.
  • HIV incidence was 5.1 per 100 person-years in 2000, falling to 0.4 per 100 person-years in 2007, then rising somewhat to 1.8 per 100 person-years in 2008.
  • HIV incidence declined by 0.06 cases per 100 person-years annually prior to 2000, followed by a more rapid annual decrease of 0.24 cases per 100 person-years thereafter.
  • Observed behavioral trends included increasing cocaine and heroin use and decreasing proportions of IDUs reporting any syringe sharing or sharing with a person known to be HIV positive.
  • In a multivariate analysis, HIV seroconversion was associated with male sex, unstable housing, intravenous cocaine use, and sharing syringes or having sex with an HIV positive partner.
  • Always acquiring syringes from safe sources conferred a reduced risk of HIV infection among participants recruited after 2004, though this association was not statistically significant for earlier participants.

"The evolution of the policies has led to a reduction in HIV incidence," Bruneau told the Montreal Gazette. "Our study really shows that adapting services and opening new ways of reaching out to drug users that are at risk of HIV infection is the way to go."


J Bruneau, M Daniel, M Abrahamowicz, et al. Trends in human immunodeficiency virus incidence and risk behavior among injection drug users in montreal, Canada: a 16-year longitudinal study. American Journal of Epidemiology 173(9):1049-1058 (abstract). May 1, 2011.

Other Source
A Derfel. Needle exchange helps cut HIV rate. Montreal Gazette. April 22, 2011.