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Background & Aims High HCV treatment uptake among people at most risk of transmission is essential to achieve elimination. We aimed to characterise subpopulations of people with HCV based on drug dependence, to estimate direct-acting antiviral (DAA) uptake in an unrestricted treatment era, and to evaluate factors associated with treatment uptake among people with recent drug dependence. Methods HCV notifications in New South Wales, Australia (1995-2017) were linked to opioid agonist therapy (OAT), hospitalisations, incarcerations, HIV notifications, deaths, and prescription databases. Drug dependence was defined as hospitalisation due to injectable drugs or receipt of OAT, with indicators in 2016-2018 considered recent. Records were weighted to account for spontaneous clearance. Logistic regression was used to analyse factors associated with treatment uptake among those with recent drug dependence. Results 57,467 people were estimated to have chronic HCV throughout the DAA era. Treatment uptake was highest among those with recent (47%), compared to those with distant (38%), and no (33%) drug dependence. Among those with recent drug dependence, treatment was more likely among those with HIV (adjusted odds ratio [aOR] 1.71; 95% CI 1.24–2.36), recent incarceration (aOR 1.10; 95% CI 1.01–1.19), and history of alcohol use disorder (aOR 1.22; 95% CI 1.13–1.31). Treatment was less likely among women (aOR 0.78; 95% CI 0.72–0.84), patients of Indigenous ethnicity (aOR 0.75; 95% CI 0.69–0.81), foreign-born individuals (aOR 0.86; 95% CI 0.78–0.96), those with outer-metropolitan notifications (aOR 0.90; 95% CI 0.82–0.98), HBV coinfection (aOR 0.69; 95% CI 0.59–0.80), and >1 recent hospitalisation (aOR: 0.91; 95% CI 0.84–0.98). Conclusions These data provide evidence of high DAA uptake among people with recent drug dependence, including those who are incarcerated. Enhancing this encouraging initial uptake among high-risk populations will be essential to achieve HCV elimination. Lay summary To facilitate HCV elimination, those at highest risk of infection and transmission are a treatment priority. This study shows the successes of Australia's universal provision of DAA therapy in reducing the barriers to treatment which have historically persisted among people who inject drugs. Despite higher DAA therapy uptake among those with recent drug dependence, gaps remain. Strategies which aim to reduce marginalisation and increase treatment uptake to ensure equitable HCV elimination must be advanced.

Population-level uptake of direct-acting antiviral (DAA) treatment for hepatitis C virus (HCV) infection, including retreatment, can be estimated through administrative pharmaceutical dispensation data. However, the reasons for retreatment are not captured in these data. We developed a machine learning model to classify retreatments as reinfection or treatment failure at a national level.Retreatment data from the REACH-C cohort (n = 10,843 treated with DAAs; n = 320 retreatments with known reason), were used to train a random forest model. Nested cross validation was undertaken to assess model performance and to optimise hyperparameters. The model was applied to data on DAA retreatment dispensed during 2016-2021 in Australia, to identify the reason for retreatment (treatment failure or reinfection).Average predictive accuracy, precision, sensitivity, specificity and FWe used a novel methodology with high classification accuracy to evaluate DAA retreatment patterns at a national level. Increases in retreatment uptake for treatment failure corresponded to the availability of pangenotypic and salvage regimens. Increasing retreatment uptake for reinfection likely reflects increasing reinfection incidence.This study used machine learning methodologies to analyse national administrative data and characterise trends in HCV retreatment due to reinfection and treatment failure. Retreatment for reinfection increased over time, reflecting increasing numbers of people at risk for reinfection following HCV cure. Increased retreatment for treatment failure corresponded to the availability of pangenotypic and salvage DAA regimens. The findings of this study can be used by public health agencies and policy makers to guide and assess HCV elimination strategies, while the novel methodology for monitoring trends in HCV retreatment has the potential to be used in other settings, and health conditions.

Background & Aims The advent of direct-acting antivirals (DAAs) has led to ambitious targets for hepatitis C virus (HCV) elimination. However, in the context of alcohol use disorder the ability of DAAs to achieve these targets may be compromised. The aim of this study was to evaluate the contribution of alcohol use disorder to HCV-related decompensated cirrhosis in three settings. Methods HCV notifications from British Columbia, Canada; New South Wales, Australia, and Scotland (1995–2011/2012/2013, respectively) were linked to hospital admissions (2001–2012/2013/2014, respectively). Alcohol use disorder was defined as non-liver-related hospitalisation due to alcohol use. Age-standardised decompensated cirrhosis incidence rates were plotted, associated factors were assessed using Cox regression, and alcohol use disorder-associated population attributable fractions (PAFs) were computed. Results Among 58,487, 84,529, and 31,924 people with HCV in British Columbia, New South Wales, and Scotland, 2,689 (4.6%), 3,169 (3.7%), and 1,375 (4.3%) had a decompensated cirrhosis diagnosis, and 28%, 32%, and 50% of those with decompensated cirrhosis had an alcohol use disorder, respectively. Age-standardised decompensated cirrhosis incidence rates were considerably higher in people with alcohol use disorder in New South Wales and Scotland. Decompensated cirrhosis was independently associated with alcohol use disorder in British Columbia (aHR 1.92; 95% CI 1.76–2.10), New South Wales (aHR 3.68; 95% CI 3.38–4.00) and Scotland (aHR 3.88; 95% CI 3.42–4.40). The PAFs of decompensated cirrhosis-related to alcohol use disorder were 13%, 25%, and 40% in British Columbia, New South Wales and Scotland, respectively. Conclusions Alcohol use disorder was a major contributor to HCV liver disease burden in all settings, more distinctly in Scotland. The extent to which alcohol use would compromise the individual and population-level benefits of DAA therapy needs to be closely monitored. Countries, where appropriate, must develop strategies combining promotion of DAA treatment uptake with management of alcohol use disorders, if World Health Organization 2030 HCV mortality reduction targets are going to be achieved. Lay summary The burden of liver disease has been rising among people with hepatitis C globally. The recent introduction of highly effective medicines against hepatitis C (called direct-acting antivirals or DAAs) has brought renewed optimism to the sector. DAA scale-up could eliminate hepatitis C as a public health threat in the coming decades. However, our findings show heavy alcohol use is a major risk factor for liver disease among people with hepatitis C. If continued, heavy alcohol use could compromise the benefits of new antiviral treatments at the individual- and population-level. To tackle hepatitis C as a public health threat, where needed, DAA therapy should be combined with management of heavy alcohol use.