Is it worth it?

Relatively young 20 year old with ms here. Just looking for a bit of advice. I had a relapse in January which was the first one that ever made me feel disabled. Fortunately, I’ve snapped back to normal at the moment but my specialist thinks it’s time for treatment. Tysabri is the one that’s been put forward but am unsure because of the pml risk so just wondering if it’s worth the risk?


The short answer to that question is ‘probably yes’.

With disease modifying drugs, you do indeed have to weigh up the risks versus the benefits. In its early days, no one knew about the risk of PML from Tysabri. Later, everyone knew of the risk so it felt a bit Russian Roulette-y (I took it briefly at this time before a different side effect took me off it!).

Nowadays however, the neurological world knows so much more about the drug, the risks and the likelihood of a given individual getting PML.

In order to contract PML, you must have the antibodies for a virus called John Cunningham, or JCV. JCV is very very common, it’s not a virus with symptoms, so without specific testing for it, you’d never know you’d come into contact with it.

The fact of being JCV+ became the factor that people had to consider when starting (or not starting) Tysabri. At that time if you were JCV negative the chance of developing PML were 1 in 10,000 (there was still a small risk because you could still encounter JCV). The chance of PML if you were JCV+ was unknown, but to be JCV+ and remain on the drug was scary. But some very clever scientists figured out a way to really fine tune the JCV testing. They can now work out a much finer, more individual risk factor. It can be estimated at less than 1 in 10,000 (ie less than if you were negative!) or as bad as 1 in 125.

Oh and in any case, no one has developed PML regardless of JCV status within 2 years of being on Tysabri.

Have a look at JC virus and PML | MS Trust

There are of course other possible side effects from Tysabri. I developed elevated liver enzymes (ie hepatitis). Some people develop an allergic reaction. There are other risks associated. But a stonking good safety profile overall as well as an excellent relapse reduction rate makes me think it’s one of, if not the, best DMDs.

What you need to do is consider all your options. Have a look at MS Decisions aid | MS Trust You can weigh up all the various drugs, see what might fit with your lifestyle and what you feel comfortable with.

Best of luck.


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Hello, I have just started on Tysabri and they are telling me its one of the best drugs to be on, also they check if you have the virus before starting and through-out. I would say go with it as I’ve heard such good things.


I’ve been scared about PML as well.
I was thinking to refuse the treatment but then my MS nurse encouraged me to get on with it.
On the 17/05/2021 I had my first dose with Tysabri. No side effects, felt absolutely normal.
I am trying to stay positive.
Take care x .