forth and religious organizations such as the Catholic Church. In the United States NEP programmes have proliferated, despite lack of public acceptance. Internationally, needle exchange is widely accepted. Research Disease transmission Two 2010 'reviews of reviews' by a team originally led by Norah Palmateer that examined systematic reviews and meta-analyses on the topic found insufficient evidence that NSP prevents transmission of the hepatitis C virus, tentative evidence that it prevents transmission of HIV, and sufficient evidence that it reduces self-reported risky injecting behaviour. In a comment Palmateer warned politicians not to use her team's review of reviews as a justification to close existing programmes or to hinder the introduction of new needle-exchange schemes. The weak evidence on the programmes' disease prevention effectiveness is due to inherent design limitations of the reviewed primary studies and should not be interpreted as the programmes lacking preventive effects. The second of the Palmateer team's 'review of reviews' scrutinised 10 previous formal reviews of needle exchange studies, and after critical appraisal only four reviews were considered rigorous enough to meet the inclusion criteria. Those were done by the teams of Gibson (2001), Wodak and Cooney (2004), Tilson (2007) and Käll (2007). The Palmateer team judged that their conclusion in favour of NSP effectiveness was not consistent with the results from the HIV studies they reviewed. The Wodak and Cooney review had, from 11 studies of what they determined as demonstrating acceptable rigour, found 6 that were positive regarding the effectiveness of NSPs in preventing HIV, 3 that were negative and 2 inconclusive. However a review by Käll et al. disagreed with the Wodak and Cooney review, reclassifying the studies on NSP effectiveness to 3 positive, 3 negative and 5 inconclusive. The US Institute of Medicine evaluated the conflicting evidence of both Drs Wodak and Käll in their Geneva session and concluded that although multicomponent HIV prevention programmes that include needle and syringe exchange reduced intermediate HIV risk behavior, evidence regarding the effect of needle and syringe exchange alone on HIV incidence was limited and inconclusive, given "myriad design and methodological issues noted in the majority of studies." Four studies that associated needle exchange with reduced HIV prevalence failed to establish a causal link, because they were designed as population studies rather than assessing individuals. NEPs successfully serve as one component of HIV prevention strategies. Multi-component HIV prevention programmes that include NSE reduce drug-related HIV risk