Masks “... along with other measures, such as aggressive quarantining of contacts” and social distancing.
Most countries have mask requirements, even the ones that “failed to contain” the spread. Everywhere I go in Maryland people are wearing masks even in the most idiotic situations. New York, New Jersey, Michigan, etc. all have masks requirements for public places and places like these had the worst outcomes for Covid 19. Maybe a mask can help prevent the spread in certain situations but as public policy it doesn’t seem to do much good. Most of the spread occurs in homes and in work situations where people are close together for extended periods. Walking by someone on Fifth Ave. is not a spreader event. I think the virus is going to go where it wants to go, which it appears to have done, until it dies out, which it seems to be doing.
Average age of death in the u.s. is 76+/-
Average age of Covid death is about the same.
Perhaps there’s another reason than masking that Vietnam did so well. Perhaps it’s the general health of the population? The u.s. has a sedentary and overweight population. Obesity is a key co-morbidity for Covid 19.