Injection drug use is the primary mode of transmission for hepatitis C virus (HCV) infection. Prior studies suggest opioid agonist therapy may reduce incidence of HCV among people who inject drugs, however, little is known about its effects in younger injectors.
To evaluate whether opioid agonist therapy was associated with a lower incidence of HCV in a cohort of young adult injectors.
Observational cohort study conducted January 2000 through August 2013 with quarterly interviews and blood samples.
San Francisco community outreach.
Young adult injectors (<30 years old) who were anti-HCV negative.
Recent (within past 3 months) substance use treatment: no treatment, non-opioid agonist forms of treatment, or opioid agonist therapy (methadone or buprenorphine) detoxification or maintenance.
Main Outcome(s) and Measure(s)
Incident HCV infection documented with a new positive HCV RNA result and/or a positive anti-HCV result. Cumulative HCV incidence rates and 95% confidence intervals were calculated assuming a Poisson distribution. Cox Proportional Hazards models were fit adjusting for age, gender, race, years of injection drug use, homelessness and incarceration.
Baseline characteristics of the sample (n=552) were: median age 23 (IQR: 20–26), 32% female, 73% Caucasian, 40% did not graduate high school, and 69% were homeless. Over the observation period of 680 person-years (py), there were 171 incident cases of HCV (incidence rate=25.1/100 py; 95% CI: 21.6–29.2). The rate ratio was significantly lower for participants who reported recent maintenance opioid agonist therapy (0.31; 95% CI: 0.14–0.65), but not for those who reported recent non-opioid agonist forms of treatment (0.63; 95% CI: 0.37–1.08), or opioid agonist detoxification (1.45; 95% CI: 0.80–2.69). After adjustment for other covariates, maintenance opioid agonist therapy was associated with lower relative hazards for becoming infected with HCV over time (AHR=0.39; 95% CI: 0.18–0.87).
Conclusions and Relevance
In this cohort of young adults who inject drugs, recent maintenance opioid agonist therapy was associated with lower incidence of HCV. Maintenance treatment with methadone or buprenorphine for opioid use disorders may be an important strategy to prevent spread of HCV among young injectors.