There was a time, not too long ago, when Congress had banned D.C. from using federal and municipal funds to operate syringe-exchange clinics, a bulwark in the fight against HIV/AIDS. Advocates eventually got the ban lifted in 2007, allowing local organizations like Bread for the City, HIPS, and PreventionWorks! (now closed) to provide clean needles and screening to users.

Today, researchers at George Washington University have published a study showing that lifting the ban and instituting a District-wide needle-exchange program produced tangible social benefits. The study, which appears in the journal AIDS and Behavior, finds that during the first two years of D.C.’s program (2008 through 2010) 120 people avoided contracting HIV from using needles. In turn, District taxpayers saved an estimated $44 million because they did not have to foot the bill for those individuals’ lifetime HIV treatment costs through publicly funded health plans. The study records a 70 percent decline in newly diagnosed HIV cases over that two year period.

“Needle exchanges are tremendous for marginalized populations who don’t have access to health care,” says Monica Ruiz, lead author of the study and an assistant research professor at GWU. “A lot of services can happen at that meeting. My takeaway: Exchanges save lives and money.”

The researchers used data collected by the District Department of Health as part of a surveillance program that tracked injection-drug-use-associated HIV between September 1996 and December 2011. They modeled the effect of removing the funding ban on needle-exchange programs in D.C. on HIV incidence, setting May 2008 as the “interruption” date—that is, when the District actually started to distribute clean syringes through its exchange.

Ruiz notes that needle exchanges typically connect users with HIV testing, condoms, and even testing for Hepatitis-C, which one can also contract from needle use. This battery of services and health education makes such programs “user-friendly,” she says, “meeting people where they’re at.” Though D.C.’s program cost $650,000 at the outset, the net savings it generated amounted to a big return on investment, she adds: “It’s helping the people already using [drugs] stay healthy.”

The study comes just a few months after Indiana’s Scott County saw an outbreak of HIV related to injection-drug use and created a needle-exchange program to reduce transmission of the virus. In the District, HIV-prevalence remains high, despite the fact that new diagnoses dropped 40 percent between 2009 and 2013: More than 16,000 residents, or about 2.5 percent of the population, lived with HIV as of 2013. (The World Health Organization defines a “generalized epidemic” as any case where HIV occurs in over one percent of the population.)

D.C.-based advocates say more research and prevention programs are needed to beat HIV/AIDS. Meghan Davies, chief of operations and program integration at Whitman-Walker Health, one of the District’s most historically visible community-health centers for those affected by the virus, says it’s important that science backs up policy decisions like D.C.’s needle-exchange program, called DC NEX.

William McColl, director of health policy at AIDS United, says D.C. has been on the right track.

“The [GWU] study shows it was the right decision to scale up syringe exchanges in the District,” McColl says. “The city should continue to make those resources available. We have a lot of work to do, but the end of the epidemic could be in sight with enough will and effort and I would even say attention to folks who are often missing from this dialogue: young African-American men who have sex with men, women who may not have the ability to access care, and a few others.”

D.C. removed 696,000 needles from the streets through its syringe-exchange programs in 2014.

Screenshots from AIDS and Behavior study.