If it does not stop it all, it is a failure.
No it is not. There are several other factors at play. The rule of the odds says that the more pathogen that is deposited into the environment, the more likely likely you are to encounter it. Then, recent research is showing that the viral load has much to do with the severity of the illness. Add a face covering to the would be recipient, and a more of the pathogen can be trapped before making it into their body.
It only takes ONE phoockin cell to infect.
How the phluck do you quantify something that is less than one micron being blocked by masks that can't block even size four microns?
And no protection for eyes, ears or other parts of the anatomy?
Shooting BB's through chain link fences.
Stop drinking the coolaid.
