"Although model projections can only provide estimates of health benefits and costs, such analyses can provide intuition around critical mechanisms and assumptions to inform decision making. Our main finding is that, over 20 y, high coverage (enrollment of 50% of the eligible population) of OAT [Opioid Agonist Therapy], NSPs [Needle and Syringe Programs], and Test & Treat in combination could avert nearly 43,400 (95% CI: 23,000, 74,000) HIV infections among PWID [People Who Inject Drugs] and reduce HIV prevalence among PWID by 27% (95% CI: 12%, 45%).

"This analysis presents the first study, to our knowledge, to quantitively examine the impact of SSP closure on HIV incidence using a modeling approach. In a rural American setting that had previously experienced an HIV outbreak among PWID, our modeling results suggest that closing an existing SSP would likely lead to a rebound HIV outbreak, with a 1.6-fold increase in incident infections among PWID in 5 years relative to SSP sustainment.

"Syringe services programs are harm reduction programs that provide a wide range of services including, but not typically limited to, the provision of new, unused hypodermic needles and syringes and other injection drug use supplies, such as cookers, tourniquets, alcohol wipes, and sharps waste disposal containers, to PWID.

"In this study, there was no indication that needle-exchange use was associated with increasing drug use. Indeed, IDUs who were former users of the exchange were more likely than never-users to report substantial reductions in drug use or stopping injection altogether. Our analysis also suggested that among heroin injectors, needle-exchange participation was wholly compatible with the goals of drug treatment.

"Methods

"The research literature on the effectiveness of syringe services programs in controlling HIV transmission among persons who inject drugs and guidelines for syringe services program that are 'functioning very well' were used to estimate the cost-saving threshold at which a syringe services program becomes cost-saving through preventing HIV infections versus lifetime treatment of HIV.

Editor's Note: This article has the following correction:

"Effective treatment has increased life expectancy after HIV infection, and deaths from non-AIDS-related causes now exceed deaths from AIDS for those with HIV in the US [35]. Medical costs of treating HIV-infected individuals as they age now include costs of both HIV-related and HIV-unrelated medical care. We estimated the medical cost saved by averting one HIV infection in the United States, taking into account the costs that would have been incurred by similar at-risk individuals in the absence of HIV infection.

"This study indicates that the SSP+MOUD [Syringe Service Program + Medications for Opioid Use Disorder] combination program is an effective harm-reduction strategy to prevent HCV cases among opioid IDUs and is cost-effective if payers are willing to pay $4,699 or more per avoided case of HCV.

"The infectious disease consequences of injection drug use place a heavy toll on entire communities and are a serious threat to the health and well-being of our nation.

"Our systematic review identified 55 NSP unit cost estimates from 14 middle and high-income countries. Higher unit costs were associated with countries with higher HSRI and fewer syringes distributed, and with newer programs, which confirmed our hypothesis. The number of intervention components included was not seen to affect the unit cost, possibly because the majority of programs did not include any additional WHO-recommended intervention components. Using our best performing model, the cost per syringe distributed of a comprehensive NSP was extrapolated to 137 countries.