[wozniacki]

Solely addressing the mask use part of your reply, I've found that it greatly helped reduce the number of times I fell ill ( even mildly ) from things you list like colds, coughs, sore throats & fatigue.

I can't believe that there are no substantial studies that have studied the ability of consumer grade surgical masks ( and/or N95s) in preventing common illnesses, very reliably when used regularly.

Why aren't these things conclusively studied, beyond any degree of doubt?

[kubb]

Most likely because it's hard to orgainze a controlled, large-scale trial, and there are many variables that influence real-world outcomes, and the measurement of the mask variable is not accurate based solely on historical real-world data.