are you listings the only difference is wearing masks? you can’t know. the choir may have all gone out to eat somewhere together or shared a pot luck. they may have gone to a mutual third place where they contracted it. there may have been contaminated surfaces in the choir loft that a mask would have been useless for. You don’t and can’t know. same with the beauty shop. cleaning surfaces and other measures may and likely were far more important than masks. Your anecdotal report proves nothing t
As far as the NEJM article if masks are useless with health care professionals who know how to fit and wear them with medical grade masks the stuff you see in the grocery store is even less effective. You can use your magic talisman anyway you want but you cannot claim science behind it. There is none
They did not do that. It shows you haven't researched this.