Earlier quoted context omitted.
> People are told to wear surgical masks, which say on the side of the box that they do not protect against viruses, because it is something they can do. It likely has some protection, and it inhibits the onward spread of the virus. If enough people wear them, it has a protective effect on the entire population: “The preponderance of evidence indicates that mask wearing reduces transmissibility per contact by reducin…
Wearing a grocery bag instead of a condom will likely also reduce your risk of unwanted pregnancy, that doesn't translate into being effectively protective. Masks help lower droplets and aerosol in the air from your breath. So they slow the contagion. But they do not stop it, if the average person were likely to contract a contagion within 6 months with normal behavior and a mask reduces transmissibility by 50%, this…
FFPs are known highly effective in protecting people both ways against virus this large, more or less indefinitely, assuming there's no operational error. Trouble being that apparently USA cannot make enough of them.
Mind you, operational error is likely over longer timespans.