The official benchmark of a hepatitis C virus (HCV) cure, an undetectable viral load 12 weeks after treatment, is a largely surefire indicator of an enduring cure. Very few people subsequently experience viral relapse after this point, developing a detectable viral load by 24 weeks after completing hep C therapy.

Publishing their findings in Clinical Infectious Diseases, researchers analyzed data from 11 Phase III clinical trials including 3,004 people with HCV who were treated with Harvoni (ledipasvir/sofosbuvir) or Sovaldi (sofosbuvir) and achieved a sustained virologic response (an undetectable viral load) 12 weeks after completing therapy (SVR12, considered a cure).

Out of this group, 12 people had a detectable hep C viral load 24 weeks after treatment. Genetic testing found that seven of these individuals had been successfully cured of the virus but were reinfected with a different strain after completing treatment. The other five individuals (0.17 percent of the total cohort) experienced viral relapse. The same virus they had before beginning treatment persisted in the liver or another part of the body and reemerged in the blood by 24 weeks posttreatment. 

To read the study abstract, click here.