Individuals who inject cocaine and methamphetamine and men who have sex with men (MSM) with high sexual risk had the greatest chance of hepatitis C (HCV) reinfection after sustained virologic response (SVR) in a large Canadian cohort. The reinfection rate did not wane over time.
The potency of direct-acting antivirals (DAAs) for HCV infection has propelled their scale-up to groups at higher reinfection risk after SVR. A recent meta-analysis found a higher reinfection rate in HCV/HIV-coinfected people than in HCV-monoinfected patients. But that analysis included only four highly diverse studies of reinfection in coinfected individuals. To get a better understanding of HCV reinfection risk in a representative community population of HCV/HIV-coinfected people, researchers working with the Canadian Co-infection Cohort conducted this study.
The Canadian Co-infection Cohort is an ongoing prospective study of more than 1600 coinfected people at 18 centers across Canada. Cohort member make twice-yearly visits. This analysis focused on coinfected people who achieved SVR since January 2003 and had at least one follow-up visit with an HCV RNA assessment. Follow-up continued until reinfection, last study visit or July 2016.
The researchers used Bayesian Cox regression to estimate reinfection incidence according to reinfection risk: "Recent high-frequency injection drug use (IDU)" meant self-reported injection of cocaine or methamphetamine in the past six months; "low-frequency IDU" meant injection of other drugs (mainly opiates); "recent high-risk sexual behavior in MSM" meant more than one sex partner and less than 100% condom use in the past six months; "low-risk MSM" were MSM without these traits. The researchers also created a reference group of men who were not MSM, not Aboriginal and did not inject drugs.
The analysis considered 257 coinfected people who had at least one post-SVR HIV RNA assay. Most study participants, 82%, were men, 74% had an IDU history, 14% actively injected drugs and 33% reported being MSM. Median age at SVR was 49 years. Eighteen people (7%) became reinfected with HCV in a median time of 2.5 years for an unadjusted reinfection rate of 31 per 1000 person-years. Five of the 18 spontaneously cleared their HCV and 13 became chronically infected. Twelve reinfections occurred in IDU and six in MSM. Five of six MSM appeared to be reinfected sexually and one through IDU.
Adjusted HCV reinfection rates per 1000 person-years in the first year after SVR were 10 for reference patients, 16 for low-risk MSM, 22 for low-frequency IDU, 26 for high-risk MSM and 58 for high-frequency IDU. Reinfection rate per 1000 person-years was 12 in the first year after SVR, 18 in years one to three and 16 after three years. Compared with reference patients, high-frequency IDU had a six-fold higher reinfection risk (hazard ratio [HR] 6.1, 95% confidence interval [CI] 2.5 to 12). High-risk MSM had almost a doubled risk, but this association was not significant (HR 1.8, 95% CI 0.56 to 4.4).
Because the reinfection rate did not diminish over time since SVR, the researchers stress that regular monitoring is essential, especially for people who remain at high risk. They note that 93% of cohort members achieving SVR did not became reinfected. Thus, they believe their results "should not serve to discriminate against offering HCV therapy to coinfected persons but rather should guide clinicians and policy makers on how best to intervene in order to reduce risk and identify subgroups that need more frequent monitoring."