Thirty years of research shows that exchange programs decrease HIV and hepatitis C transmission by up to 50%, said Stacey McKenna, a fellow with the right-leaning think tank R Street Institute based in Washington, D.C.

Participants are four to five times more likely to “enter treatment and stay in treatment,” she said. “They are three times more likely to stop using drugs.”

Opponents included GOP Sen. Richard Cash, who said the exchange program seemed to offer tacit approval for drug usage.

“Not everybody is ready for abstinence,” McKenna replied. “Right now, their life is still valuable even if they’re still continuing to do this.”