How strong is Tecfidera really?

So I've been diagnosed with MS in January. My doctor prescribed me the med Tecfidera in like March. I've not been ill a lot since then but the influenza season is yet to come and I got myself some vitamine pills today so I won't be sick so much. I just realized when I came back to my therapeutic shared apartment that it might be counterproductive to have a med that puts my immune system down and take something to tune it up again. The nurse here asked me though if I want to be sick from now till February, I asked her if tecfidera is really that strong and has those effects. She said it's pretty strong. What is your experience with this medication and what can you recommend?