[tacocataco]

I was under the impression that masks only work to protect you from transmitting to others. Has that aspect not been studied yet?

Or are you talking about the efficacy of masks protecting the person that wears it?

Appreciate your time.

[ryanmcbride]

The largest reduction in rate of transmission is when the infected person is wearing a mask. However if both the infected, and uninfected person are wearing masts, it drops just a little bit lower. But you're right that if an unmasked infected person comes in contact with a masked healthy person, the masked person is still very likely to get infected.

[xapata]

It's much like flossing. The mechanism is so obvious, we didn't need a statistical study to be confident. We now have statistical evidence from Covid-19 spread.

[tomp]

No idea. I’m not an expert.

My physics intuition says that air filter is almost equally effective whereever it is (your mouth or another person’s mouth). It depends on the details though - how big the virus is? How far does it travel? How much of it comes out “dry” vs in water droplets? How big are these water droplets? What’s the distance it can travel in a droplet vs “dry”? And so on and so on. My prior says that eyes aren’t a big transmission factor (as the virus has particular affinity towards lung cell receptors) and that the only way that mask efficiency is radically different depending on who’s wearing it is, if the virus is mostly exhaled in water droplets and most of them evaporate in the next 1-2 meters (so when you inhale through a mask, it doesn’t filter the tiny virus particles, whereas exhaling into a mask does filter the less tiny water droplets).

But the bigger point is, it doesn’t matter. Masks can help, and that should be enough to make a decision, like a general rule or recommendation to wear masks (or face coverings).