Roche reported today on a long-term follow-up study of patents who achieved SVR to prior therapy. Of the 997 patients followed for a mean duration of 4.1 years following an SVR, 989 of them (99.2%) were PCR-negative at the end of the follow-up period.
My guess is that some or all of the 8 patients who had detectable HCV were re-infected as opposed to having a relapse.