They have to check also if you have antibodies of the chicken pox prior starting Gilenya.
I did the switch 4 months ago and I feel great. I didn't have a relapse, even if the efficancy is lower than Tysabri (50% vs 70% for Tysabri). I was too scared of the PML risk. This one is much safer. I always have a bottle of a sanitizer with me, I'm being careful without going crazy