I took Avonex for a year and a half and when I went off of it because of pregnancy I was worried about the side effects coming back, too.
When I started back on it my side effects didn't come back, I was so happy!

I'm on Tysabri now, no side effects but I still have 3 doses of Avonex sitting in my fridge... trying to figure out what to do with it.
Good luck!