Coronavirus: Mask mandates limit spread, study finds

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The Canadian study found that mask mandates can limit the spread of COVID-19 by 25 to 46 percent.

Mask mandates can help protect the public from transmission of the COVID-19 coronavirus, according to a Canadian study.

The study was performed by Simon Fraser University (SFU) Department of Economics researchers and found that mask mandates are associated with a 25 percent or larger weekly reduction in COVID-19 cases, according to a news release.

While the study is still in preprint and has not gone through peer review, it found that if a nationwide indoor mask mandate had been implemented in early July, the weekly number of new cases in Canada could have been reduced by 25 to 40 percent in mid-August, or by between 700 and 1,100 cases, the release says.


The researchers looked at how mask mandates were applied across Ontario’s 34 Public Health Units (PHUs), and found that in the first few weeks after mask mandates were adopted they were associated with an average weekly reduction of 25 to 31 percent in newly identified COVID-19 cases relative to the PHUs which did not adopt mask mandates, the release says.

A countrywide analysis found that province-level data shows that a significantly negative association between mask mandates and subsequent case growth, specifically up to a 46 percent average reduction in new cases, the release says.

“Jointly, these results suggest that mandating indoor mask wear in public places is a powerful policy measure to slow the spread of COVID-19, with little associated economic disruption in the short term,” the release says.

The study also found that relaxed restrictions on businesses and gatherings had a positive association with increased COVID-19 infections, while more stringent restrictions in these areas was associated with a weekly decrease in new infections by 48 to 57 percent, the release says.

While the authors note that their sample period doesn’t allow them to definitively say whether the effects of mask mandates persist or weaken beyond the first few weeks following implementation, they conclude that, along with other policy measures, it can be a potent tool for slowing the spread of the disease.