Here's an interesting article. Interesting to me as my Neuro is quite convinced that I should be taking Tysabri rather than one of the Interferons. I've always been less convinced due to the link with PML which has now been re-assessed since the clinical trails which put the risk as 1 in 1,000 to 1.2 per 10,000. It still doesn't change my mind about taking the drug... to me any risk is too much risk, but interesting to read all the same.
Incidence Of PML With Tysabri In Multiple Sclerosis Lower Than Previously Thought