A new research review finds strong evidence that needle-exchange programs reduce the sharing and reuse of dirty needles among drug addicts, but less-than-compelling data about the programs’ effectiveness in reducing the spread of HIV, Reuters reported March 11.

Researcher Norah Palmateer of the U.K. National Health Service said that limited studies of needle exchange tentatively show that the programs reduce HIV transmission; findings regarding spread of hepatitis C were gauged to be insufficient by the reviewers.

Palmateer said the fault may not lie with the concept but rather with the study designs, which have tended to be observational rather than controlled clinical trials. “The findings of this review should not be used as a justification to close NSPs (needle and syringe programs) or hinder their introduction,” said Palmateer.

The findings were published in the journal Addiction.