Grant: CIHR Fellowship

North America is experiencing unprecedented rates of overdose. Preventing people from initiating injection drug use would reduce the burden of overdose mortality and prevent transmission of HIV and other blood-borne infections. However, to-date, few interventions are known prevent injection drug use initiation. Opioid agonist treatments (OAT), including methadone maintenance treatment and buprenorphine/naloxone, have demonstrated range of benefits, including reductions in injection drug use and HIV risk behaviours. Preliminary studies have likewise demonstrated a protective effect of OAT engagement on the provision of injection initiation assistance by people who inject drugs (PWID) to injection-naïve persons. However, gaps in evidence remain related to the feasibility of this approach across various subgroups of PWID. This is an important gap in understanding given the use of OAT modalities for preventing injection initiation may vary in effectiveness across diverse populations. In particular, some PWID experience complex, overlapping forms of social and economic inequities, increasingly recognized as underlying drivers of drug-related harm and barriers to accessing health and social services. This proposed multisite research program aims to a) examine the extent to which groupings of socioeconomic factors shape injection initiation practices in distinct settings, and b) assess OAT's potential role in preventing injection initiation across marginalized subgroups of PWID. It will employ a comparative approach with data from multiple cohorts of PWID based in Toronto, Canada and the binational metropolitan unit of Tijuana, Mexico/San Diego, USA. It is anticipated that the proposed work will provide insight into how effective and adaptable the approach to "Addiction Treatment as Prevention" is for preventing injection initiation across diverse settings and populations of PWID, thus mitigating upstream drivers of drug-related health disparities in Canada and abroad.