Dear @Jesse95252, I'm not sure one can "control" JCV as such. Rest assured that your doctors will be monitoring your level via blood tests. Having JCV doesn't automatically mean PML is inevitable. I read a very interesting article recently about the incidence of PML, following Tysabri infusions. It seems that you are lucky to be American. Because everyone in the world who takes Tysabri is given the same dose, the prevalence of PML is much higher in Eastern countries (in Asia for example) where the people tend to be smaller and lighter. Bigger, heavier Westerners have a much lower incidence of PML as the dose of Tysabri, in respect to body size, is much lower. Try spacing out the interval between doses as much as you can, too. When I first started Tysabri I had it every four weeks. Now I go six or seven weeks between infusions. Good luck, and best wishes, Jon

Hi, my PVC is from the beginning at 1, 4. It doesn't change at all.