They actually are not giving odds; they are saying <1/1000-this could be 1/1001 or 1/7500-it could be any number more than 1000. See what I mean?
For me I try not to think about it too much

I want whatever knowledge I can attain and make my best decision at the time. pml is rare-not for those that got it but, it is rare..chances of heart disease, cancer are much higher. ms sucks and Tysabri has held it at bay for me. Thank G-d for Tysabri !!!
This is what I think
Linda