It's my understanding that Tysabri isn't as immunosuppressive as some other DMTs because of the way it works (it targets t-cells rather than B-cells) though you're still eligible for anti virals if you get covid and the vaccine. I've been on it for about a year and had covid a few weeks ago, and was much less ill with it than the time before when I was on a more immunosuppressive DMT! Do what you're comfortable with (some people find mask wearing just good practice regardless of how 'at risk' they are!) but don't feel like you need to stop living your life! (I've been on DMTs for 15 years and outside of covid, never taken any particular precautions)

Yes you are now immunocompromised similarly to how a whole bunch of us are including myself. Just slightly less so than others like myself and on different medications. Natalizumab modify white blood cells. It it makes them less effective at doing very specific things, but the side effect to that is the white blood cells do not attack and kill other things as well anymore. I'm on slightly different medication than yours, but I have been on a number of the mab ending the immune compromising medications because they are a disease modifier by changing how your body fights any internal problems with the blood cells that fight things. (White blood cells are our immune systems “big gun” defence tool). Using disease modifiers can be a trial and error to find the best fit disease modifier for you. It can sometimes take years as things can take 4 to 6 months to begin to really tell if things are working better or different at all in a symptom management way simply because things don't get worse. Please be more cautious, catching a cold can be very unpleasant and has led me to ICU a number of times even before I was on ocrevus but other medications closer to what you take. I wear a six layer activated carbon mask that filters like an N95 as well whenever I am out and about doing any errands or going to meet up with people in a group in public. Now I don't catch any colds, and that has been wonderful wonderful. For myself it is worth the hassle of wearing a mask to not catch any more colds ever again, let alone something like the flu. The primary reason I like the activated carbon instead of not having activated carbon is I live in an area that has year-round forest fires and the carbon completely prevents the smoke from making it through the mask. It also prevents cigarette smoke and related too. It prevents most other smells and things bound up in air making it through the n95 filter as well. Wearing an N95 at least when you are in a busy, crowded place or closed environment with a lot of people or animals will be helpful.