Yes, a small number of people have died from PML (progressive multifocal leukoencephalopathy), the infection that can be triggered from the JC virus when a carrier is taking Tysabri (or other chemo-like treatments). As of September 2011, 159 people have contracted PML and, of these, 29 have died. This is out of thousands of people who are on Tysabri. No one has died in the UK. Standards of care in the UK of patients on Tysabri are very controlled and generally excellent. There are procedures in place to quickly stop PML too, if contracted.
The risks of getting PML depend on whether or not you carry the JC virus (about 54% of people do I think, and 2% of non-carriers catch it every year) and whether or not you have ever had steroids (if you have, it increases the risk of getting PML if you carry the JC virus). The other factor is how many infusions of Tysabri you have had. The chances of getting PML if you don’t carry the JC virus are zero. The chances of getting PML during the first year of having Tysabri are almost zero even if you have the virus and have had steroids in the past. The chances of getting PML increase in the second year of Tysabri and again in the third year. They seem to fall after that. (I’ve got the numbers somewhere, but can’t remember them off hand. If you want them, I will have a look.)
It all sounds scary, but it’s important to recognise the chances of getting PML even if you carry the JC virus are very very small. The average risk is 1 in 1000 I think. The average risk of dying from PML when taking Tysabri therefore must be about 1 in 18000, or 0.0056%. (I think my maths is right, but my brain is not at its best today!)
There is a new blood test for the JC virus. If you are negative, then you cannot get PML. (However, you could catch the virus any day so there is no guarantee.)
Tysabri is WAY above the other DMDs in terms of reducing relapses and progression. A lot of patients also find that existing symptoms improve while they are on Tysabri - this doesn’t happen on any other DMD.
So it’s a very scary chance of PML versus a very scary almost certainty of your MS getting worse.
Of course, I’m not on Tysabri (I wasn’t eligible) so it’s easy for me to stay all cold and objective about it. It’s a really tough decision, no doubt and when I thought I might have the chance of going on Tysabri I was very confused about what to do. However, there isn’t a med in existence that doesn’t have side effects, and I bet there isn’t one that hasn’t cause fatalities - even things as everyday as cough meds can kill.