In December, Congress quietly made a huge change to help combat HIV: It effectively lifted the federal funding ban on needle exchange programs, which provide clean needles — meaning syringes that aren't infected with HIV — to drug users.

The change, reported by John Stanton at BuzzFeed on Tuesday, keeps the federal funding ban on syringes themselves, but ends the ban on all other aspects of the programs — staff, vehicles, gas, rent, and so on. Activists praised the move as an effective end to the ban, since the syringes are a very inexpensive part of needle exchange programs.

The ban's end was spearheaded by two Kentucky Republicans, House Appropriations Chair Hal Rogers and Senate Majority Leader Mitch McConnell, in large part as a response to an HIV crisis in Indiana and a heroin epidemic nationwide. Last year, the worst ever HIV epidemic in Indiana prompted Republican Gov. Mike Pence to allow needle exchange programs in his state. And with the worsening heroin epidemic, federal lawmakers were purportedly worried that growing addiction to the needle-injected drug could make HIV spread further.

Congress originally imposed the ban in the late 1980s in response to the HIV/AIDS epidemic of that era, based on now-disproven concerns that providing clean needles to drug addicts could enable more drug use and make drug and HIV epidemics worse. Congressional Democrats briefly lifted the ban in 2009, but Republicans put it back in place in 2011 after they took over the House of Representatives.

Clean needle exchanges are a proven way to fight the spread of HIV

Syringe exchanges allow people to obtain clean needles for little to no cost. The idea is to get dirty needles off the streets while supplying drug users with needles that won't carry the risk of an HIV or hepatitis infection.

These programs are proven to substantially reduce, although not eliminate, the rate of HIV infections from needles. A 1998 study from researchers at Johns Hopkins University found clean needle exchanges generally reduced the spread of HIV without increasing drug use. A 2004 study from the World Health Organization, which analyzed two decades of evidence, produced similar results.

When Washington, DC, adopted a needle exchange program to combat its HIV epidemic, needle-caused HIV cases dropped by 80 percent, from 149 in 2007 to 30 in 2011, according a report from the DC Department of Health.

Critics of needle exchanges argue the programs increase illegal drug use by expanding access to syringes used for drugs. But the World Health Organization's 2004 review of the research found no convincing evidence to support that claim.

The end of the congressional funding ban essentially comes around to this research — right as there are signs that these programs are needed the most.