Transforming community health advocates into peer interventionists: a binational harm reduction model.

Background: Community Health Advocates (CHAs) are widely employed as outreach workers for people who use drugs (PWUD), yet there is limited evidence on how to design capacity-building interventions that strengthen peer-driven behavior change in binational border settings. This study examined a structured capacity-building model that trained peer CHAs in Ciudad Juárez, Mexico, and El Paso, Texas to deliver an HIV prevention and skills-building intervention to PWUD and assessed its impact on HIV risk and protective behaviors. Methods: We employed two complementary evaluation methods: (1) a quantitative survey with participants, and (2) in-depth interviews with CHAs. Quantitatively, generalized linear models estimated effects of intervention participation on condom procurement, procurement of sanitized syringes, and condomless sex with substance-using partners, followed by a path model testing whether receipt of HIV prevention information mediated the association between peer-attributed behavior change and condomless sex. Qualitatively, in-depth semi-structured interviews with CHAs, analyzed using a rapid qualitative approach, explored how CHAs experienced training and evolving roles, and how they perceived peer communication and information diffusion as mechanisms of change. Results: CHAs assumed expanded responsibilities, including delivering rapid HIV testing, organizing community events targeting structural determinants of HIV risk, and implementing peer-driven, network-based behavioral interventions; over time, they evolved into peer navigators and recovery coaches, facilitating linkage to harm reduction, HIV care, and overdose prevention while maintaining cultural and linguistic congruence with binational PWUD communities. Higher levels of peer-attributed behavior change were strongly associated with receiving a broader range of HIV prevention information topics, and greater receipt of information was associated with lower levels of condomless sex. Peer-attributed behavior change exerted a significant indirect effect through receipt of information, while qualitative data highlighted how trust, lived experience, and incremental practice changes supported these pathways. Conclusion: A structured, culturally attuned capacity-building model can transform CHAs into peer interventionists, navigators, and recovery coaches who deliver network-based HIV and overdose prevention strategies in binational settings. Peer-attributed behavior change appears to reduce condomless sex primarily by increasing exposure to HIV prevention information, underscoring information diffusion through peer networks as a key mechanism for lowering HIV-related sexual risk in marginalized cross-border communities.