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.