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. 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.

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.

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 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.