Hepatitis C incidence among patients attending primary care health services that specialise in the care of people who inject drugs, Victoria, Australia, 2009 to 2020

Background: Monitoring trends in hepatitis C virus (HCV) incidence is critical for evaluating strategies aimed at eliminating HCV as a public health threat. We estimate HCV incidence and assess trends in incidence over time among primary care patients. Methods: Data were routinely extracted, linked electronic medical records from 12 primary care health services. Patients included were aged ≥16 years, tested HCV antibody negative on their first test recorded and had at least one subsequent HCV antibody or RNA test (January 2009–December 2020). HCV incident infections were defined as a positive HCV antibody or RNA test. A generalised linear model assessed the association between HCV incidence and calendar year. Results: In total, 6711 patients contributed 17,098 HCV test records, 210 incident HCV infections and 19,566 person-years; incidence was 1.1 per 100 person-years (95% confidence interval (CI): 0.9 to 1.2). Among 559 (8.2%) patients ever prescribed opioid-related pharmacotherapy (ORP) during the observation period, 135 infections occurred during 2,082 person-years (incidence rate of 6.5 per 100 person-years (95% CI: 5.4 to 7.7)). HCV incidence declined 2009–2020 overall (incidence rate ratio per calendar year 0.8 (95% CI: 0.8 to 0.9) and among patients ever prescribed ORT (incidence rate ratio per calendar year 0.9, 95% CI: 0.75 to 1.0). Conclusion: HCV incidence declined among patients at primary care health services including among patients ever prescribed ORP and during the period following increased access to DAA therapy. Among a retrospective cohort of ∼6,700 primary care health services patients, this study estimated a hepatitis C virus (HCV) infection incidence of 1.1 per 100 person-years (95% confidence interval: 0.9 to 1.2). HCV infection incidence declined between 2009 and 2020.