Philadelphia’s syringe exchange — the only one in the city, and one of just a handful operating around the state — prevented an estimated 10,592 HIV diagnoses in its first 10 years of operation, researchers at George Washington University have found.

The study, published Tuesday in the Journal of Acquired Immune Deficiency Syndrome, used mathematical modeling to estimate how the 1992 opening of the needle exchange, Prevention Point, affected the spread of HIV in the city. Without the exchange, the study found, Philadelphia would have seen 15,248 HIV diagnoses associated with injection drug use between 1993 and 2002.

Instead, the city reported 4,656 diagnoses in that time.

The study’s lead author, Monica Ruiz, said the research shows the efficacy of such harm-reduction measures — and also how changes in public policy can directly impact the health of a city.

“There’s a lot of evidence showing that harm reduction works,” said Ruiz, an associate professor in the department of prevention and community health at GW’s Milken Institute School of Public Health. “What we forget to look at is the structural factors that put such interventions into place. To have city support, revenue, and partnership with health departments — it does have true epidemic impact. Needle exchanges save lives.”

But additional data from the city health department Tuesday shows that current drug trends are sending HIV diagnoses up again. In 2016, new HIV diagnoses among intravenous drug users hit an all-time low — but then increased from 33 new cases in 2016 to 71 new cases in 2018, a 115% increase.

Between 2015 and 2016, only 5% of newly diagnosed HIV infections occurred among people who inject drugs. By 2018, 17% of the city’s new HIV diagnoses occurred in that population. (In 1992, the year Prevention Point opened, about 30% of the city’s new HIV diagnoses stemmed from injection drug use.)

Health officials said that access to drug treatment, Prevention Point’s needle exchange program, and behavioral changes among long-time drug users were likely behind the decades-long drop in HIV cases stemming from injection drug use. Yet as the crisis in Philadelphia has worsened, more people have begun to inject drugs, the department said.

The powerful synthetic opioid fentanyl, which has replaced most of Philadelphia’s heroin supply, is also behind the rise in HIV infections, the department said. Fentanyl has a shorter half-life than heroin, meaning that it sends drug users into withdrawal faster.

As a consequence, people in opioid addiction who were used to injecting a few times a day are injecting every few hours to stave off the pain, nausea, and cravings of withdrawal. Requiring more injections, they’re now more likely to share syringes or re-use old ones.

» READ MORE: Infections, the hidden danger of the opioid crisis, are on the rise in Philadelphia

Prevention Point opened at the height of the AIDS crisis, amid an alarming rise in HIV diagnoses among people who injected drugs, largely through sharing used needles. HIV is a virus spread via blood and other body fluids that attacks the immune system, and if left unchecked can lead to the late-stage condition, AIDS. Medication therapies enable people to live with HIV for decades, but must be taken for life.

Though state law prohibited syringe distribution, pressure from activists led then-Mayor Ed Rendell and the city health department to defy state officials and open the exchange in August 1992. Today, Prevention Point offers addiction treatment, overdose prevention, and other health services in addition to its syringe exchange operation in Kensington. Its workers also hand out clean needles from vans around the city.

“There’s proof [in this study] that syringe exchanges work,” said Jose Benitez, executive director of Prevention Point. (Benitez was listed as a co-author of the study because the researchers used information from his organization.) “The HIV cases we diverted would have cost [the city] millions to take care of people in their lifetime. This structural intervention we have, exchanging a used syringe for an unused one, is both averting disease and saving taxpayer dollars.”

Needle exchanges are still illegal in Pennsylvania, though programs have since opened in Pittsburgh and smaller cities. Some operate mostly underground, with the tacit approval of sympathetic officials.

Both Benitez and Ruiz said they saw parallels between the fight to open needle exchanges and the more recent push in several cities to open supervised injection sites, places where people can use drugs under medical supervision, be revived if they overdose, and access treatment. Benitez is also the president of Safehouse, the nonprofit working to open a site in Philadelphia.

“What the study indicates to us is that although sometimes this kind of harm reduction can be seen as radical, in practice we really are helping people take better care of themselves, and as such, the community gets better,” Benitez said.

Ruiz said that it’s crucial for researchers to account for local, state, and federal policy when they study the efficacy of public health interventions, and said she hopes her research will resonate with policymakers.

“If we don’t look at the policies that hinder people from accessing the care they need, from doing the things they need to do to stay healthy, when those folks fail, we end up blaming the victim,” she said. “You can’t tell people, ‘Hey, don’t share needles,’ when they don’t have access to a syringe exchange and it’s not legal."