Opioid agonist treatment and the process of injection drug use initiation.

•Persons who inject drugs (PWID) who reported opioid agonist treatment (OAT) enrollment had lower odds of recently initiating others into injection drug use (IDU).•Younger age was associated with an increased risk of initiating others into IDU.•Findings suggest a potential role for OAT to prevent incident cases of IDU initiation.