Not sure if you caught the bit where Claire's dad got shot - something which would have destroyed something along the lines of 40% of his brain (considering he was shot at basically point blank range). If Claire's blood alone can regenerate 40% of someone's brain, I'm fairly sure you'd have to decapitate their head and bury it in liquid steel to prevent them from regenerating their entire bodies again. I mean, we're talking massive cellular regeneration here.
We might see one of them die though, and that'd prove one of the sides here right. =P
We might see one of them die though, and that'd prove one of the sides here right. =P