[oldalum]

I and I think others have mentioned in previous threads a few contact tracing case studies in which masks seemed to be protective (a full South Korean mask wearing evacuation flight with something like 6 not-known-at-the-time asymptomatic but infectious people who only infected one other passenger over 11 hours, someone who was not sitting near any of the infected people but took off her mask in a restroom used by one of the infected people), a McDonald's or something in South Korea in which one infected person who sat under an air conditioner for 2 hours infected numerous other customers who came and went but not the two employees who were there for 8 hours and wore masks the whole time). No one of these case studies is definitive (e.g., airplane bathroom transmission could have been fomite) but together they are fairly convincing, at least to me, that masks (especially N95) are highly protective against aerosol infection and transmission. Which makes sense, that is what they are supposed to do. Keep in mind that we can't do randomized controlled trials on effectiveness of masks; the evidence is going to be imperfect.

[oldalum]

I and I think others have mentioned in previous threads a few contact tracing case studies in which masks seemed to be protective (a full South Korean mask wearing evacuation flight with something like 6 not-known-at-the-time asymptomatic but infectious people who only infected one other passenger over 11 hours, someone who was not sitting near any of the infected people but took off her mask in a restroom used by one of the infected people), a McDonald's or something in South Korea in which one infected person who sat under an air conditioner for 2 hours infected numerous other customers who came and went but not the two employees who were there for 8 hours and wore masks the whole time). No one of these case studies is definitive (e.g., airplane bathroom transmission could have been fomite) but together they are fairly convincing, at least to me, that masks (especially N95) are highly protective against aerosol infection and transmission. Which makes sense, that is what they are supposed to do. Keep in mind that we can't do randomized controlled trials on effectiveness of masks; the evidence is going to be imperfect.