[semi-extrinsic]

If there was definite evidence that wearing masks helped prevent catching flu, at the very least you would see them used in occupations where the cost of an employee being out with the flu for a week is very high. Since we don't see this, they are probably ineffective.

[m3kw9]

You need to wear it properly, some if not all regular people adjust their mask looser so they can breathe easier