Most research on masks so far has involved medical settings or households with a person known to be infected, said Dr. Mark Loeb, a McMaster University professor who studies infectious diseases and recently reviewed the evidence on masks and the spread of respiratory illnesses.
When it comes to mask wearing in the wider community, most studies published in scientific journals don’t show a clear impact so far, possibly because of factors such as study size, he said.
He said that the Public Health Agency of Canada’s advice on masks is pragmatic and “a wise thing to do.” But he questioned whether the evidence on universal mask wearing is strong enough to make it mandatory in all public places, although, he said, mandating it on transit may be reasonable.
Tan said we don’t have the “luxury of time” to wait for that kind of evidence. “During a pandemic, you need to be looking at the emerging evidence and look at other levels of evidence to say there is more than enough science behind it.”