Cost-effectiveness of a police education program on HIV and overdose among people who inject drugs in Tijuana, Mexico

Background Incarceration is associated with drug -related harms among people who inject drugs (PWID). We trained >1800 police officers in Tijuana, Mexico on occupational safety and HIV/HCV, harm reduction, and decriminalization reforms (Proyecto Escudo). We evaluated its effect on incarceration, population impact and costeffectiveness on HIV and fatal overdose among PWID. Methods We assessed self -reported recent incarceration in a longitudinal cohort of PWID before and after Escudo. Segmented regression was used to compare linear trends in log risk of incarceration among PWID pre -Escudo (2012-2015) and post -Escudo (2016-2018). We estimated population impact using a dynamic model of HIV transmission and fatal overdose among PWID, with incarceration associated with syringe sharing and fatal overdose. The model was calibrated to HIV and incarceration patterns in Tijuana. We compared a scenario with Escudo (observed incarceration declines for 2 years post -Escudo among PWID from the segmented regression) compared to a counterfactual of no Escudo (continuation of stable pre -Escudo trends), assessing costeffectiveness from a societal perspective. Using a 2 -year intervention effect and 50 -year time horizon, we determined the incremental cost-effectiveness ratio (ICER, in 2022 USD per disability -adjusted life years [DALYs] averted). Findings Compared to stable incarceration pre -Escudo, for every three-month interval in the post -Escudo period, recent incarceration among PWID declined by 21% (adjusted relative risk = 0.79, 95% CI: 0.68-0.91). Based on these declines, we estimated 1.7% [95% interval: 0.7%-3.5%] of new HIV cases and 12.2% [4.5%-26.6%] of fatal overdoses among PWID were averted in the 2 years post -Escudo, compared to a counterfactual without Escudo. Escudo was cost-effective (ICER USD 3746/DALY averted compared to a willingness -to -pay threshold of $4842-$13,557). Interpretation Escudo is a cost-effective structural intervention that aligned policing practices and human -rights -based public health practices, which could serve as a model for other settings where policing constitutes structural HIV and overdose risk among PWID. Funding National Institute on Drug Abuse, UC MEXUS CONACyT, and the San Diego Center for AIDS Research (SD CFAR). Copyright (c) 2024 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY -NC -ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).