The series is getting boring damn quick. Nothing new or interesting is being done with the vamps and we were given an incredibly bad "I survive by magic!" speech by Bill.
No attempt at a scientific explanation for vamps in this world. Magic.
That explains how someone with no working circulatory system or glands could have an erection, too. Making vamps impotent would sure taking a wrecking ball to their mythos, though.
I wonder if Bill has even taken a dump in over 150 years. "I don't shit, Sookie."