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How Well Do Needle Exchange Programs Work?


Needle and syringe programs have been widely adopted as a harm reduction measure to reduce the transmission of HIV, hepatitis B and C, and other blood-borne infections among injection drug users (IDUs). But evidence for the effectiveness of such interventions is "weaker than given credit for in the literature," and better-designed studies are needed, according to a review of reviews published in the May 2010 issue of Addiction. The authors of an accompanying editorial, however, argued that sterile syringe access "is certainly good enough" to recommend it as a key element in efforts to prevent infection among IDUs.


Norah Palmateer from Health Protection Scotland and colleagues in England reviewed existing evidence about the effectiveness of harm reduction interventions that involve providing sterile injecting equipment for prevention of HIV and hepatitis C virus (HCV) among injection drug users.

The study authors performed systematic searches of English language literature through March 2007 to identify systematic, narrative, or meta-analytical reviews (also known as a "review of reviews") of the impact of harm reduction interventions on HIV transmission, HCV transmission, and/or injecting risk behaviors. They looked at needle and syringe programs, alternative methods of needle/syringe distribution (such as pharmacies, vending machines, and outreach programs), and provision of injection equipment other than needles and syringes (for example, "cookers" to mix drugs and clean rinse water).

Reviews were classified as either high quality (core) or supplementary. A framework based on quality of reviews, reviewers' conclusions, and the designs and findings of the primary studies was used to derive evidence statements.


  • The researchers identified 3 core and 2 supplementary reviews of injection equipment interventions.
  • According to the proposed framework, the study found "tentative evidence" to support the effectiveness of needle and syringe programs in preventing HIV transmission.
  • There was "insufficient evidence" to conclude that any of the interventions are effective in preventing HCV transmission.
  • There was "sufficient evidence" to support the effectiveness of needle and syringe programs (and tentative evidence of an additional impact of pharmacy distribution) in reducing self-reported injecting risk behaviors.
  • There was "little to no evidence" on the effectiveness of vending machines, outreach, or providing injection equipment other than needles/syringes.

Based on these findings, the study authors concluded, "The evidence [for harm reduction interventions] is weaker than given credit for in the literature. "

"The lack of evidence for effectiveness of needle and syringe programs vis-à-vis biological outcomes (HCV and HIV incidence/prevalence) reflects the limitations of studies that have been undertaken to investigate these associations," they continued. "Particularly for HCV, low levels of injecting risk behavior may be insufficient to reduce high levels of transmission. New studies are required to identify the intervention coverage necessary to achieve sustained changes in blood-borne virus transmission."

Investigator affiliations: Health Protection Scotland, Glasgow, UK; Department of Social Medicine, University of Bristol, Bristol, UK; Centre for Research on Drugs and Health Behaviour, London School of Hygiene and Tropical Medicine, London, UK; Department of Statistics and Modelling Science, University of Strathclyde, Strathclyde, UK.


In an accompanying editorial, Ricky Bluthenthal from the RAND Corporation and Alex Kral from RTI International's Urban Health Program argued that the primary justification for the Palmateer team's conclusion is that the vast majority of research on needle and syringe provision has used observational study designs.

Because observational and ecological studies of HIV prevalence, incidence, and injection risk behaviors suggest potential benefits, many researchers believe it would be unethical to conduct controlled trials in which some injection users are randomly assigned to receive clean needles and others are not.

"Because more rigorous research designs are not likely to be conducted on sterile syringe access interventions at this time," Bluthenthal and Kral wrote, "there is no rational justi?cation to discount the utility of such interventions."

However, they continued, "local, regional and federal governments all over the world have failed to protect the health of their peoples by allowing their stigmatization of drug users to justify ignoring common sense syringe access interventions."

The editorial authors suggested a 3-part agenda for improving harm reduction for IDUs. First, they suggested that specific local environmental conditions should be studied more closely, for example social network size, the impact of law enforcement, and connections between IDUs and other high-risk populations. Second, they wrote, "quality improvement studies of sterile syringe access are needed desperately," to learn how best to maximize coverage.

"Research that considers the effectiveness of increasing sterile syringe access should include making syringes available at more venues, in different settings, as well as using existing IDU drug-using and social networks to distribute syringes to IDUs unwilling or unable to access them at conventional locations," they recommended.

Third, they noted, several studies have suggested that sexual risk behaviors are more important than injecting behaviors for transmitting HIV among IDUs, and harm reduction programs therefore should explore promising sexual risk reduction interventions -- beyond condom distribution -- at needle and syringe program sites.

"Sterile syringe access will not prevent every potential HIV or HCV transmission event, but it contributes invariably to lower injection risk, can be a singularly useful venue for providing other recommended health promotion activities and is certainly good enough, given the preponderance of evidence to recommend it widely as a critical element in efforts to prevent blood-borne infection among IDUs," they concluded.



N Palmateer, J Kimber, M Hickman, and others. Evidence for the effectiveness of sterile injecting equipment provision in preventing hepatitis C and human immunodeficiency virus transmission among injecting drug users: a review of reviews. Addiction 105(5): 844-859 (Abstract). May 2010.

R Bluthenthal and A Kral. Commentary on Palmateer et al. (2010): next steps in the global research agenda on syringe access for injection drug users. Addiction 105(5): 844-859. May 2010.