You can explain the physics to a mask-denier over and over and over.

I remember seeing video during the early part of the pandemic of an anti-masker getting up in some city council meeting where they were discussing the need for wearing masks. He yelled and jabbed his finger at the council, saying "if I fart you're going to smell if through that mask, right!" He thought he had an ironclad example of how masks would fail to protect against covid. Perfect Dunning-Kruger bozo.

And regarding the safety of the vaccines... in a matter of a few weeks I had two different people tell me that "40,000 people had been turned into vegetables" by the vaccine. What struck me is that they had the exact phrasing and totally erroneous figure for something that had not happened. This stuff circulates among people who just have no critical thinking skills. Sponges that just absorb whatever crap they come across, the crazier the better.