KINGSTON, R.I. — Aug. 27, 2025 — Young black men who have sex with men experience a disproportionate burden of HIV infection—as high as one in two—despite advances in HIV treatment and prevention, and that risk of infection is heightened among those who use illicit substances. University of Rhode Island College of Pharmacy Professor Ashley Buchanan’s new study aims to provide novel insights for HIV interventions among such marginalized populations and show the potential of “spillover” benefits among study subjects’ peers.

Funded by a $3.5 million, five-year R01 grant from the National Institutes of Health, the project is a multi-institution collaboration including Buchanan, Natallia Katenka and Jing Wu at URI; Dr. John Schneider, Anna Hotton and Jonathan Ozik at the University of Chicago; Youjin Lee at Brown University; Samuel Friedman at New York University; and Eleanor Murray at Boston University.

The team is examining three studies based in Chicago that collected data on the sexual networks and sexual risk behaviors of a population of young black men, as well as information on their social networks and the neighborhoods they live in. The data sheds light on barriers to HIV treatment and prevention they face. These could include a lack of access to HIV and substance use treatment, and social stigma that can prevent individuals from seeking out treatment or prevention methods.

The study participants are frequently part of social and sexual networks that can enhance the impact of HIV interventions beyond the treated individual, Buchanan said. This “spillover” occurs when one participant’s exposure affects another’s health outcomes. Spillover has been evaluated for therapies like vaccines, and there is preliminary evidence that HIV interventions result in meaningful spillover, including for preventative measures like pre-exposure prophylaxis (PrEP). However, there have been limited evaluations of spillover in the population.

“The thrust of what we’re doing is trying to understand how certain interventions or even exposures that could be thought of as interventions, spill over or affect other people in the network,” Buchanan said. “For example, PrEP for HIV protects the individual from acquiring HIV. And of course, if the person doesn’t acquire HIV, it also prevents them from transmitting to their partners. So how do we engage and support individuals so they can have knowledge of and access to HIV treatment and prevention tools? Instead of just an external public health person coming in and delivering the intervention and the message, you can actually engage community leaders and other members of the community to change the norms and empower the community itself toward better health.”

Buchanan aims to assess the spillover of HIV interventions among populations that use illicit substances, using analyses of existing data and simulation approaches. The project looks at three existing data sets from surveys conducted among men who have sex with men and may also use illicit substances to try to determine the barriers to care—including access to health services and societal stigma—and the effectiveness of spillover on the use of HIV prevention methods like PrEP. The new methods developed in the project will provide a more accurate understanding of the potential impact of an intervention, leading to more efficient use of limited public health resources.

The project engages a community advisory board on the development of culturally relevant HIV interventions among men who have sex with men, integrating the findings into comprehensive HIV prevention programming. The project also engages representatives from the AIDS Foundation Chicago to discuss HIV interventions among young black men who have sex with men and expedite public health implementation of interventions.

“Evaluation of spillover will help advance progress toward the goals of the End the HIV Epidemic Initiative by informing impactful HIV intervention strategies among young black men who have sex with men and their networks beyond contact tracing efforts alone,” Buchanan wrote in the study summary. “The methodologies and substantive findings developed in this research will strengthen research capacity for network studies of populations at-risk for HIV by mitigating biases and, ultimately, improve how we use interventions in networks to reduce the spread of HIV and other diseases.”

The study also examines illicit substance use among the population and whether that counteracts prevention methods, especially by increasing risk behaviors. Substance use can also often lead to incarceration, especially among marginalized communities, which can inhibit access to and even knowledge of prophylactic methods, potentially impacting social networks when formerly incarcerated individuals return to their communities.

“So, it’s this multifaceted problem and traditional public health approaches alone are not making enough progress. And of course, the whole problem is infiltrated with social economic issues and stigma,” Buchanan said. “The most important component is actually being able to use these studies in collaboration with members of this population to understand the mechanisms of spillover in this particular population. Measuring spillover will address the high burden of HIV among young black men who have sex with men because it can expand the reach of HIV intervention benefits to individuals not connected to traditional research and clinical settings, while strengthening communities of young black men who have sex with men.”