Harm reduction among injecting drug users — evidence of effectiveness

This chapter synthesises and evaluates the available direct evidence relating to the impact of needle and syringe programmes (NSPs), opioid substitution treatment (OST), drug consumption rooms (DCRs), and peer naloxone distribution (PND) on HIV/hepatitis C (HCV) incidence/prevalence, injecting risk behaviour and overdose-related mortality. To achieve this, we conducted a review of reviews; a systematic and explicit method used to identify, select and critically appraise relevant findings from secondary level research (systematic reviews and/or meta-analyses) into an evidence briefing. In the absence of high-quality reviews, appraisal of the evidence was supplemented with a targeted review of the primary literature. We find that there is sufficient review-level evidence that OST reduces HIV transmission, while the evidence in support of NSPs reducing HIV transmission is more tentative, and for DCRs currently insufficient. There is tentative evidence that OST has limited effectiveness in reducing HCV transmission, and insufficient evidence to support or discount NSPs or DCRs’ ability to reduce HCV transmission. There is sufficient review-level evidence that NSPs, OST and DCRs reduce self-reported injecting risk behaviour. There is sufficient review evidence that OST reduces risk of overdose mortality, but insufficient evidence to support or discount the effect of DCRs or PND on overdose deaths at the community level. Our review shows evidence in support of a variety of harm reduction interventions but highlights an uneven presence of high-quality review evidence. Future evaluation of harm reduction programmes should prioritise methodologically robust study designs.