National trends in retreatment of HCV due to reinfection or treatment failure in Australia

•Seven percent of people treated for HCV in Australia were retreated.•Machine learning was used to classify retreatments based on national administrative data.•Overall, 52% of retreatment was for reinfection and 48% was for treatment failure.•Retreatment for reinfection increased over time, reflecting increasing numbers of people at-risk for reinfection following cure.•Retreatment for treatment failure increased when salvage DAAs became available.