It's very rare for anyone to relapse if undetectable at 12 weeks.
I just read about the the results of an earlier part of the clinical trial I'm on from the World Liver Congress meeting two weeks ago in Spain.
It gives the results for 240 people, mostly genotype 1 and 3 with a few genotype 2, after 8 weeks of treatment with MK3682, grazoprevir, & either elbasvir or MK8408.
Every single person who was SVR 12 weeks was also SVR after 24 weeks (in other words, everyone who tested undetectable after 12 weeks, was still undetectable after 24 weeks).
The first time I treated I relapsed within 4 weeks.
From what I have read the expectation after SVR12 the primary way to test positive again would be from reinfection.
I was treated with interferon based treatment 3 times with no change in viral load (null responder) I treated with Sovaldi/Olysio for 12 weeks and was found to have relapsed 12 weeks after I finished treatment. I was not tested at week 4 post.
I treated with 24 weeks Harvini and 15 weeks of Ribavirin and am now 1 year post. I was tested at 12, 24, and 44 weeks post and continue to be not decked and free of hep c.
From what I have heard the odds of relapse after SVR12 are very minimal. You have better odds to win power ball than relapse after SVR12
I've always heard that chances of relapsing after SVR12 are pretty unlikely, but I didn't know if anyone was keeping track anywhere. I am also going on a year in a few weeks. Thanks