Injection drug users are at risk of blood-borne infections like the hepatitis C virus (HCV). To reduce these harms, the distribution of sterile injection equipment and access to substitution treatments (e.g. opioid agonist therapy or OAT) remain central to preventing transmission of these diseases. But how efficacious are these strategies? A new study based on a cohort of 422 Montreal drug users reveals that a high dose of OAT (>=60mg/day methadone or >=16mg/day buprenorphine) is associated with a 77% risk reduction of HCV infection. A light dose of OAT or access to sterile injection equipment did not show significant risk reductions of HCV infection. This study is helping clinicians to better choose the appropriate dose of OAT to prevent infections in patients with drug use disorder. You can read the article published in the American Journal of Preventive Medicine here.