2. Effectiveness of drug treatment, needle and syringe programmes and drug consumption rooms in the prevention of blood-borne viruses among people who inject drugs – updated evidence from reviews of empirical and mathematical modelling studies

To update a 2011 RoR on the effectiveness of drug treatment (including opioid agonist treatment (OAT)), NSP and DCRs in preventing/reducing hepatitis C virus (HCV), HIV, injecting risk behaviour (IRB) and injecting frequency (IF) among people who inject drugs.

Part (i): We searched for systematic reviews and studies from 2011 to 2020 to identify empirical evidence for the above-named interventions/outcomes. Part (ii): We also searched for mathematical modelling studies focused on Europe for evidence on the impact of NSP and OAT on HCV transmission. Linear regression quantified the relationship between modelled OAT/NSP scaleup (‘relative reduction in gap to 100% coverage’) and impact (‘relative reduction in incidence’)

Part (i): 8,513 reviews and 7,133 studies were screened, with 31 and 61 identified as relevant, respectively. The level of evidence increased (since the 2011 RoR) and is now ‘sufficient’ for OAT (regarding all outcomes), NSP (for preventing HIV and IRB), and combination OAT/NSP (for preventing HCV). Part (ii): 4,734 studies were screened with 15 identified as relevant. With moderate reductions in the coverage gap (40%), the combined scale-up of OAT and NSP could substantially reduce HCV incidence (43%-52%) at the population level, and may have greater impact when combined with DAAs.

A strong body of empirical and mathematical modelling evidence for OAT and NSP, alone and in combination, in preventing IRB, HCV and HIV exists. However, there is still insufficient empirical evidence for other interventions examined (e.g. heroin-assisted treatment, low dead-space syringes, and others) regarding the outcomes of interest. This work was supported by an EMCDDA grant (CT.19.EU4MD.0099.1.0)