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Brown study shows suspending syringe services programs would lead to increase in HIV infections

Study uses simulation model to project HIV incidence from 2020 to 2025


Last month, a study published by University researchers used a simulation model to show that suspending syringe services programs would lead to an increase in HIV infections. 

According to the CDC website, SSPs “provide a range of services, including linkage to substance use disorder treatment; access to and disposal of sterile syringes and injection equipment; and vaccination, testing and linkage to care and treatment for infectious diseases.”

The researchers chose to model Scott County, Indiana — the center of an HIV outbreak in 2015 — after receiving an email from the CDC in May 2020 that expressed concern over the possible forced closure of SSPs in the area. The SSPs were facing a sunset clause, meaning that even though the “effectiveness of (the) SSPs has been proved by so many previous studies,” the CDC has to defend their funding annually, said Xiao Zang, a postdoctoral research associate in epidemiology who led the analysis of the study. 

“We were interested in pursuing this topic as a number of counties and local governments in the US have pulled funding for SSPs or have sought to close them altogether,” Brandon Marshall, associate professor of epidemiology and principal investigator of the study, wrote in an email to The Herald. “Harm reduction programs have always faced some political opposition, but it was particularly disheartening to see successful programs in high-need communities at risk of closure,” he added. 


Though “the gold standard of clinical studies are clinical trials, they are not always feasible or practical or ethical,” Zang said. Instead, the study built Treatment of Infectious Transmissions through Agent-based Network, a mathematical model based on historical data of HIV infections to “simulate the spread of HIV in a network of people who inject drugs,” Marshall wrote. 

TITAN is agent-based, meaning that it simulates the actions of multiple individuals to predict the impact of their interactions. This model has been used in a number of other studies to “examine the effectiveness of hypothetical HIV prevention and treatment strategies in the US,” Marshall added.

The researchers calibrated their simulation model by comparing TITAN’s predicted number of new diagnoses from 2016 to 2019 to real-world data in order to ensure the model’s credibility, accuracy and reliability, Zang said.

Afterwards, the researchers simulated how the number of HIV cases in Scott County would change from 2020 to 2025 if just one SSP was shut down “to see the actual impact of closing the SSP,” Zang added.

They found that both a temporary and permanent closure of a single SSP “would very likely lead to a rebound HIV outbreak among people who inject drugs,” Marshall wrote. “For example, we found that closing an SSP might lead to an almost 60% increase in the number of new HIV cases among people who inject drugs in a rural setting in the US.”

Closing these programs “will have devastating impacts, not just for Scott County, but also … other areas in the US, in particular rural areas where the operation and the implementation of SSPs are constantly challenged by social and structural barriers,” Zang added.

“This study is consistent with … prior research,” which demonstrates that a “lack of syringe exchange programs is absolutely linked to large (HIV) outbreaks,” said Matthew Murphy, assistant professor of medicine and behavioral and social sciences. Murphy, who was not an author on the study, is also an internal medicine physician who researches infectious disease and HIV prevention among populations that are or were formerly incarcerated.

This study adds to a “fairly rich evidence base for the effectiveness of needle and syringe exchange programs and their potential impact on reducing HIV transmission,” Murphy said. 

The CDC has identified more than 200 counties that are at high risk for an HIV outbreak. There has also been a “growing number of notable examples of (HIV) outbreaks in the United States among people who inject drugs … even in neighboring Massachusetts,” Murphy said.

 “We want to advocate for sustaining the existing SSP services,” Zang said. “By implementing more (SSPs) you are taking proactive actions to prevent these HIV outbreaks from happening in the first place.”  


“If we reduce or fail to expand needle and syringe exchange programs, it's only a matter of time before we see increasing numbers of HIV outbreaks and cases, both in Rhode Island and nationally,” Murphy said. 

“I hope this research demonstrates that SSPs are absolutely critical if we’re serious about ending the HIV epidemic in the United States. No matter where they live, people who inject drugs deserve access to SSPs and all forms of HIV prevention services, like pre-exposure prophylaxis, or PrEP,” Marshall wrote.

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