Background & AimsScale-up of highly-effective direct-acting antivirals (DAAs) for hepatitis C virus (HCV) among people who inject drugs (PWID) in Scotland has led to a reduction in prevalence of viraemia in this population. However, the extent of reinfection among those treated with DAAs remains uncertain. We estimated HCV reinfection rates among PWID in Scotland by treatment setting, pre and post-introduction of DAAs, and the potential number of undiagnosed reinfections resulting from incomplete follow-up testing.MethodsThrough linkage of national clinical and laboratory HCV data, a retrospective cohort of PWID who commenced treatment between 2000-2018 and achieved a sustained virological response (SVR) were followed up for reinfection to December 2019. Reinfection was defined as a positive HCV antigen or RNA test.ResultsOf 5686 SVRs among 5592 PWID, 4126 (73%) had an HCV RNA or antigen test post-SVR. Of those retested, we identified 361 reinfections (3.9/100 person-years (PY)). The reinfection rate increased from 1.5/100 PY among PWID treated in 2000-2009 to 8.8/100 PY in 2017-2018. The highest reinfection rates were observed among those treated in prison (14.3/100 PY) and community settings (9.5/100 PY). Among those treated in the DAA era (2015-2018), 68% were tested within the first year post-SVR but only 30% in the second year; while 169 reinfections were diagnosed in follow-up, an estimated 200 reinfections (54% of the estimated total) had gone undetected.ConclusionsHCV reinfection rates among PWID in Scotland have risen contemporaneous with the scale-up of DAAs and broadened access of treatment to those at highest risk, through delivery in community drug services. Promotion of HCV testing post-SVR among PWID is essential to ensure those reinfected are identified and retreated promptly.
- reinfection; HCV; PWID; sustained virological response; SVR; injecting; incidence