Younger people with recent injection drug use were more likely to experience hepatitis C reinfection after being cured, but those treated for mental illness had a lower reinfection risk, according to findings presented at the AASLD Liver Meeting.

Direct-acting antiviral therapy can cure most people with hepatitis C virus (HCV), but initial infection does not produce lasting immunity, and people can contract the virus again. Preventing HCV reinfection among people who inject drugs is central to eliminating hepatitis C in the population.

Naveed Janjua, MBBS, DrPH, of the British Columbia Centre for Disease Control, and colleagues assessed HCV reinfection rates among people treated with direct-acting antivirals. They analyzed data from the British Columbia Hepatitis Testers Cohort, a data set of approximately 1.3 million people tested for HCV. The researchers followed individuals who were treated with antiviral therapy and achieved a sustained virological response (SVR)—an undetectable HCV viral load after completing therapy—which is considered a cure. After achieving SVR, a subsequent positive HCV RNA test was considered an indicator of reinfection.

Of the 8,423 people who achieved SVR, 65% were men, and the median age was 58 years. Nearly 80% were ages 50 or older. The researchers took note of injection drug use history, classifying those with medical visits related to drug use during the past three years as recent users. Some 20% had recent injection drug use, 17% had injection drug use in the more distant past and 63% had not injected drugs. Recent injectors were younger, on average (median age 51 years), and more likely to have major mental illness, problematic alcohol use and HIV coinfection.

The researchers identified 176 cases of HCV reinfection over nearly 12,000 person-years of follow-up, for an overall reinfection rate of 1.49 cases per 100 person-years. But this differed according to drug use history. People with recent injection drug use had a higher rate of reinfection (4.39 cases per 100 person-years) compared with those with past injection drug use (1.04 cases) or no injection drug use (0.54 cases). The incidence of HCV reinfection rose over time, reaching 30% for people with recent injection drug use and 13% for people with past drug use at five years.

Further, the researchers found that younger people with recent injection drug use were at even higher risk for HCV reinfection following a cure (7.33 cases). People who used opioids or had HIV coinfection were also at higher risk. On the other hand, people treated with antipsychotic medications had a lower likelihood of HCV reinfection. People who consistently received opioid agonist therapy to manage addiction also had a lower reinfection risk.

“In this population-based cohort, HCV reinfection rates after direct-acting antiviral therapy were highest among persons with recent injection drug use, especially among younger people who inject drugs and those with HIV coinfection,” the researchers concluded. They suggested that younger people may need more support for reinfection prevention.

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