The impact of syringe services program closure on the risk of rebound HIV outbreaks among people who inject drugs: A modeling study

Objective:Despite their effectiveness in preventing the transmission of HIV among people who inject drugs (PWID), syringe services programs (SSPs) in many settings are hampered by social and political opposition. We aimed to estimate the impact of closure and temporary interruption of SSP on the HIV epidemic in a rural United States setting.Methods:Using an agent-based model (ABM) calibrated to observed surveillance data, we simulated HIV risk behaviors and transmission in adult populations who inject and do not inject drugs in Scott County, Indiana. We projected HIV incidence and prevalence between 2020 and 2025 for scenarios with permanent closure, delayed closure (one additional renewal for 24 months before closure), and temporary closure (lasting 12 months) of an SSP in comparison to persistent SSP operation.Results:With sustained SSP operation, we projected an incidence rate of 0.15 per 100 person-years among the overall population (95% simulation interval: 0.06-0.28). Permanently closing the SSP would cause an average of 58.4% increase in the overall incidence rate during 2021-2025, resulting in a higher prevalence of 60.8% (50.9-70.6%) (18.7% increase) among PWID by 2025. A delayed closure would increase the incidence rate by 38.9%. A temporary closure would cause 12 (35.3%) more infections during 2020-2021.Conclusion:Our analysis suggests that temporary interruption and permanent closure of existing SSPs operating in rural United States may lead to 'rebound' HIV outbreaks among PWID. To reach and sustain HIV epidemic control, it will be necessary to maintain existing and implement new SSPs in combination with other prevention interventions.