Hepatitis C reinfection following treatment induced viral clearance among people who have injected drugs.

BACKGROUND: Although people who inject drugs (PWID) are an important group to receive Hepatitis C Virus (HCV) antiviral therapy, initiation onto treatment remains low. Concerns over reinfection may make clinicians reluctant to treat this group. We examined the risk of HCV reinfection among a cohort of PWID (encompassing all those reporting a history of injecting drug use) from Scotland who achieved a sustained virological response (SVR).

METHODS: Clinical and laboratory data were used to monitor RNA testing among PWID who attained SVR following therapy between 2000 and 2009. Data were linked to morbidity and mortality records. Follow-up began one year after completion of therapy, ending on 31st December, 2012. Frequency of RNA testing during follow-up was calculated and the incidence of HCV reinfection estimated. Cox proportional hazards regression was used to examine factors associated with HCV reinfection.

RESULTS: Among 448 PWID with a SVR, 277 (61.8%) were tested during follow-up, median 4.5 years; 191 (69%) received one RNA test and 86 (31%) received at least two RNA tests. There were seven reinfections over 410 person years generating a reinfection rate of 1.7/100py (95% CI 0.7-3.5). For PWID who have been hospitalised for an opiate or injection related cause post SVR (11%), the risk of HCV reinfection was greater [AHR=12.9, 95% CI 2.2-76.0, p=0.002] and the reinfection rate was 5.7/100py (95% CI 1.8-13.3).

CONCLUSION: PWID who have been tested, following SVR, for HCV in Scotland appear to be at a low risk of reinfection. Follow-up and monitoring of this population are warranted as treatment is offered more widely.