Hrm. I guess we don’t have any really solid PF on the subject. Bugger.
Anyhow, my thoughts on the subject. Note that these are based on a modern understanding of what a virus is and how it works. Any and all of it might go out the window due to things working a little differently in EVE.
In the process of reproducing, viruses destroy the host cell. This then spits out more little viruses that go after the adjacent cells, infecting them, altering them to make more virus, and then killing them to release the newly manufactured baddies. Generally, what makes you sick is this ongoing cell death. What makes a virus dangerous depends on which cells specifically in the body that it attacks.
What this means for Vitoc: Yes, viruses alter the genetic makeup of the infected cell in order to make more virus. However, they don’t automatically change the genetic makeup of every cell in your body – only the ones which have been infected. By the time the virus has reproduced enough times to infect all those billions (trillions?) of cells in the body, it should have killed enough of them that you’re dead anyways.
Therefore, it should be possible, even in the most extreme cases of vitoxin infection and vitoc dependence, to find at least a handful of uninfected cells in the body from which to make a clone. Now, this doesn’t do any good for the psychological dependence upon vitoc (apparently it’s a hell of a high) which in turn requires vitoxin infection to be effective, leading to some potentially really fucked up cases of people being freed from vitoxin only to be voluntarily infected again so they can get their vitoc fix.
Again, that’s based on the rather detailed description of Vitoxin as a virus and the way viruses work. They don’t infect every single cell in the body – you’re dead long before that can occur. But this is EVE, so who knows? Not even CCP.