The researchers estimate much higher effectiveness among older adults (~20% for both 65-74 and 75+ year-olds vs. Observational studies and surveys report about two-fold high rates of face covering usage among older adults versus younger adults and minors.

Rather, estimates reflect the effectiveness of face coverings and the impact of this public health intervention in reducing transmission at the population level, which also depends on the usage rate of face coverings, whether face coverings are properly used, the amount of time face coverings are used, in addition to mask efficacy. The researchers note their estimates differ from those measuring how effective face coverings can prevent COVID-19 infection when used correctly. However, if everyone wore masks in the same degree and manner as older adults, the city could reduce overall transmission by as much as 28–32 percent.

If the city maintained the same usage rates of face coverings in April into the reopening period starting June 8, the researchers estimate that face coverings would reduce overall COVID-19 transmission by approximately 9–11 percent during reopening when people spend a greater amount of time outside homes and use face coverings outside. Face Coverings Are Key to a Safer Reopening The New York City study finds reducing contact rates was highly effective for most age groups-contributing to at least a 50 percent reduction in transmission across age groups, ranging from a 51 percent reduction among 1-4 year-olds to 83 percent among 5-14 year-olds. The new study is in line with previous modeling studies estimating that lockdowns reduced COVID-19 transmission by 58 percent in Wuhan, China, 45 percent in Italy, and 77 in France. The study by scientists at Columbia University Mailman School of Public Health and the New York City Department of Health and Mental Hygiene appears ahead of peer review in the preprint server medRxiv. Widespread use of face coverings contributed an additional 7 percent reduction, and up to 20 percent reduction among those aged 65 and older during the first month face covering was mandated in public places. Reducing contact rates-mainly via school closures and voluntary or mandated stay-at-home measures-contributed to around a 70 percent reduction in the transmission of COVID-19 in New York City during the spring pandemic wave from March to the June reopening.

Will there be another lockdown in nyc