If you look into the filtration effects of p1/2/3 filters and compare the pore size with the molecular size of virus spores and bacteria you might find it elightening bro
Common sense is all that is required...not a study. If you put a filter mask sealed over your nose and mouth that can act as a barrier for 0.2 particles and Sars/Covid virus is 0.7 to 0.9 (
estimated).....what does that tell you bro ?
Of course though nothing is truly 100% effective against viruses and bacetria unless you wear a hazmat suit and an oxygen tank but a proper mask with filtration is doing quite a lot to keep the user safe from bacteria and viruses and other spores.
Put it this way....if I had to go and sit in a hospital waiting room these days for a few hours for treatment I would rather wear a proper mask than sit there like a dumb shit who was conviced that he/she was immune to every virus on the planet coz their body had built up herd immunity over decades and they are now invincible.
It's a no brainer decision !