I was on Tysabri for 6 or 7 years, and JC positive the whole time. Both my neuro and I were happy for me to carry on, as it was doing a good job. Eventually though, my titre level of JC began to rise. This, combined with the length of time I’d been on it, meant my neuro said I was at a pretty high risk of getting PML. She would have let me carry on, but I decided to make a switch. I’m on Tecfidera now, which is daily pills. It’s not quite as good as Tysabri, but I’m still relapse free after 3 years.
When you see your neuro, I’d ask what level your JC virus is, and what kind of risk that puts you at. If you’re happy to carry on, then ask your neuro if they’re happy too. But if you do decide to come off, talk to your neuro about the different options - how effective they are, how they’re taken, possible side effects etc. Then ask for a bit of time to think about it and weigh everything up, and ask on here for people’s experiences of the different ones.