Background: It is unknown what levels of preexposure prophylaxis (PrEP) use are needed to reduce racial disparities in HIV incidence among men who have sex with men (MSM). Using an agent-based model, we quantified the impact of achieving PrEP coverage targets grounded in equity on racial disparities in HIV incidence among MSM in an urban setting in the Southeastern United States. Methods: An agent-based model was adapted to simulate HIV transmission in a network of Black/African American and White MSM aged 18–39 years in the Atlanta–Sandy Springs–Roswell metropolitan area over 10 years (2015–2024). Scenarios simulated coverage levels consistent with targets based on the ratio of the number of individuals using PrEP to the number of individuals newly diagnosed in a calendar year (i.e., the ‘PrEP-to-need ratio’), ranging from 1 to 10. Incidence rate ratios and differences were calculated as measures of disparities. Results: Without PrEP, the model predicted a rate ratio of 3.82 and a rate difference of 4.50 comparing HIV incidence in Black/African American and White MSM, respectively. Decreases in the rate ratio of at least 50% and in the rate difference of at least 75% were observed in all scenarios in which the PrEP-to-need ratio among Black/African American MSM was 10, regardless of the value among White MSM. Conclusion: Significant increases in PrEP use are needed among Black/African American MSM to reduce racial disparities in HIV incidence. PrEP expansion must be coupled with structural interventions to address vulnerability to HIV infection among Black/African American MSM.

Pre-exposure prophylaxis (PrEP) for HIV prevention may not only benefit the individual who uses it, but also their uninfected sexual risk contacts. We developed an agent-based model using a novel trial emulation approach to quantify disseminated effects of PrEP use among men who have sex with men in Atlanta, USA from 2015 to 2017. Components (subsets of agents connected through partnerships in a sexual network, but not sharing partnerships with any other agents) were first randomized to an intervention coverage level or control, then within intervention components, eligible agents were randomized to PrEP. We estimated direct and disseminated (indirect) effects using randomization-based estimators and reported corresponding 95% simulation intervals across scenarios ranging from 10% to 90% coverage in the intervention components. A population of 11,245 agents was simulated with an average of 1,551 components identified. Comparing agents randomized to PrEP in 70% coverage components to control agents, there was a 15% disseminated risk reduction in HIV incidence (95% simulation intervals = 0.65, 1.05). Individuals not on PrEP may receive a protective benefit by being in a sexual network with higher PrEP coverage. Agent-based models are useful to evaluate possible direct and disseminated effects of HIV prevention modalities in sexual networks.

Background: We examined the impact of expanded access to medications for opioid use disorder (MOUD) in a unified prison and jail system on post-release, opioid-related overdose mortality. Methods: We developed a microsimulation model to simulate a population of 55,000 persons at risk of opioidrelated overdose mortality in Rhode Island. The effect of an extended-release (XR) naltrexone only intervention and the effect of providing access to all three MOUD (i.e., methadone, buprenorphine, and XR-naltrexone) at release from incarceration on cumulative overdose death over eight years (2017-2024) were compared to the standard of care (i.e., limited access to MOUD). Results: In the standard of care scenario, the model predicted 2385 opioid-related overdose deaths between 2017 and 2024. An XR-naltrexone intervention averted 103 deaths (4.3% reduction), and access to all three MOUD averted 139 deaths (5.8% reduction). Among those with prior year incarceration, an XR-naltrexone only intervention and access to all three MOUD reduced overdose deaths by 22.8% and 31.6%, respectively. Conclusions: Expanded access to MOUD in prison and jail settings can reduce overdose mortality in a general, atrisk population. However, the real-world impact of this approach will vary by levels of incarceration, treatment enrollment, and post-release retention.

ImportanceIn 2021, the state of Rhode Island distributed 10 000 additional naloxone kits compared with the prior year through partnerships with community-based organizations.ObjectiveTo compare various strategies to increase naloxone distribution through community-based programs in Rhode Island to identify one most effective and efficient strategy in preventing opioid overdose deaths (OODs).Design, Setting, and ParticipantsIn this decision analytical model study conducted from January 2016 to December 2022, a spatial microsimulation model with an integrated decision tree was developed and calibrated to compare the outcomes of alternative strategies for distributing 10 000 additional naloxone kits annually among all individuals at risk for opioid overdose in Rhode Island.InterventionsDistribution of 10 000 additional naloxone kits annually, focusing on people who inject drugs, people who use illicit opioids and stimulants, individuals at various levels of risk for opioid overdose, or people who misuse prescription opioids vs no additional kits (status quo). Two expanded distribution implementation approaches were considered: one consistent with the current spatial distribution patterns for each distribution program type (supply-based approach) and one consistent with the current spatial distribution of individuals in each of the risk groups, assuming that programs could direct the additional kits to new geographic areas if required (demand-based approach).Main Outcomes and MeasuresWitnessed OODs, cost per OOD averted (efficiency), geospatial health inequality measured by the Theil index, and between-group variance for OOD rates.ResultsA total of 63 131 simulated individuals were estimated to be at risk for opioid overdose in Rhode Island based on current population data. With the supply-based approach, prioritizing additional naloxone kits to people who use illicit drugs averted more witnessed OODs by an estimated mean of 18.9% (95% simulation interval [SI], 13.1%-30.7%) annually. Expanded naloxone distribution using the demand-based approach and focusing on people who inject drugs had the best outcomes across all scenarios, averting an estimated mean of 25.3% (95% SI, 13.1%-37.6%) of witnessed OODs annually, at the lowest mean incremental cost of $27 312 per OOD averted. Other strategies were associated with fewer OODs averted at higher costs but showed similar patterns of improved outcomes and lower unit costs if kits could be reallocated to areas with greater need. The demand-based approach reduced geospatial inequality in OOD rates in all scenarios compared with the supply-based approach and status quo.Conclusions and RelevanceIn this decision analytical model study, variations in the effectiveness, efficiency, and health inequality of the different naloxone distribution expansion strategies and approaches were identified. Future efforts should be prioritized for people at highest risk for overdose (those who inject drugs or use illicit drugs) and redirected toward areas with the greatest need. These findings may inform future naloxone distribution priority settings.