Preliminary results from a study conducted by Simon Fraser University researches suggests that a mask mandate can lower the transmission of COVID-19 by 25 per cent each week.

Study results, released prior to peer review on Wednesday (Oct. 7), show that mandating masks indoors nationwide in early July could have reduced new weekly cases by 25 to 40 per cent in mid-August. That would translate approximately to 700 to 1,1000 fewer cases each week.

Researchers from SFU’s economics department focused on mask mandates brought in across Ontario’s 34 Public Health Units over the course of two months this year. Results from comparing units that went to mask mandates early, versus later, showed that earlier adoption was association with an average weekly reduction of 25 to 31 per cent, in July and August. There has been no mask mandate province-wide in B.C., although many government buildings, grocery stores and other businesses have brought in mask rules of their own.

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The results of SFU’s study differed from an earlier one about mask mandates in the U.S., which found a nine to 10 per cent reduction in new cases.

“One possible explanation is that Ontario’s mask policy is more comprehensive: we evaluate the effect of universal indoor mask-wearing for the public rather than the effect of mask wearing for employees only in [the U.S. study]. Differences in the compliance rate may also contribute to this difference,” researchers noted.

An analysis of mask mandates across the country found a reduction in new cases of up to 46 per cent in the first weeks after adoption. Researchers also saw that mask mandates increased self-reported use by 30 per cent.

“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 study concluded.

Researchers also looked at COVID-19 restrictions and their effect on new cases. They found that the most stringent restrictions were associated with a decrease of 48 to 57 per cent in weekly cases.

Study authors noted that while the results are significant, “their sample period does not allow them to definitively say whether the effect of mask mandates persists or weakens beyond the first few weeks after implementation.”

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katya.slepian@bpdigital.ca

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