[TacticalCoder]

In Japan, before Covid, people did sometimes use masks but that wasn't the majority. Very far from it. If I'm not mistaken it is people who know they are sick that would wear a mask to protect others. That still doesn't work for people unknowingly carrying a virus.

And most people are unmasked: so they're still exposed to at least some pathogens. So I don't see why they'd have a compromised immune system.