Mask mandates shown to significantly reduce spread of COVID-19

A new study by Simon Fraser University (SFU) researchers has found clear evidence that wearing a mask can have a significant impact on the spread of COVID-19. The researchers, from SFU's Department of Economics, have determined that mask mandates are associated with a 25 per cent or larger weekly reduction in COVID-19 cases.

The finding of their study, still in preprint and not yet peer-reviewed, conclude that mandating indoor masks nationwide in early July could have reduced the weekly number of new cases in Canada by 25 to 40 per cent in mid-August, which translates into 700 to 1,100 fewer cases per week.

The study analysed the impact of mask mandates that were implemented across Ontario's 34 Public Health Units (PHUs) over the course of two months.

Researchers compared the results of PHUs that adopted mask mandates earlier to those that adopted mandates later. They determined that, in the first few weeks after their introduction, mask mandates were associated with an average weekly reduction of 25 to 31 per cent in newly diagnosed COVID-19 cases, relative to the trend in mask mandate absence, in July and August.