Fair enough, it was more of a curiosity thing than anything else because I had never heard of it before and was interested in whether or not some sort of system existed. I may use this in a campaign in the future in which the souls of those that become zombies go to a place in hell and are tortured by the god of undeath. Then I could use some sort of system like the one I mentioned as a way for priests and priestesses to "save" those that were turned into zombies. I'm still unsure about how vampires and things of that nature would work in a system like that, but that's beside the point.
Thanks for the info. As I said, I was mostly curious. I didn't even think about what Bizbag had mentioned about undead being immune to disease. Which pretty much means what I had said initially is impossible because their disease would have been removed. And then vampires are just created another way entirely.