https://www.city-journal.org/article/approximately-zero https://www.city-journal.org/article/approximately-zero I suspect this is the study being mentioned. K

https://www.city-journal.org/article/approximately-zero https://www.city-journal.org/article/approximately-zero I suspect this is the study being mentioned. Keep in mind this is at slowing population level spread. On an individual level masking may be different. The idea is that covid is so contagious in unexposed population that any precautions against spread are futile.