I think I see some holes in his plan

from here and here (image source)

I understand why people might want to cosplay as Bubble Boy, but there are holes for your hands to go through and the zipper isn't completely shut, and even if it was, it's not designed to keep out microscopic pathogens. Still, a little protection may be better than no protection at all (at least as long as you realize the limitations and aren't lulled into a false sense of security). Maybe this will reduce his chances of coming down with something.