From what I'm understanding, it's generally good to keep up vitamin levels regardless (I could be sooooooo much better, lol!!). But I think especially having Vit D in addition to a multi is extra beneficial. Then if you get the actual virus, you should definitely take copious amounts of Vit C, a bit extra Vit D, Zinc, and I've heard Melatonin can be helpful, too - not just for sleeping, but there is some way it can help. I did all that when I had it last year, at a period where I know my immune system was bad. I *think* I prevented from getting worse symptoms (mine were bad - but didn't go to hospital) - because I was diligent with the vitamins.