As Canadians prepare to welcome Americans across the Canada-U.S. border on Monday, Canada's top doctors are stressing that domestic COVID-19 transmission is most likely to drive a fourth wave of the pandemic.
"We’re watching the situation very carefully," Dr. Theresa Tam, Canada’s chief public health officer said at a press conference on Thursday.
"I think the domestic situation, if we’re going to get a fourth wave based on our modelling,...is likely to be driven by domestic transmission events rather than importation cases."
Dr. Tam added that as the volume of travellers has increased in Canada, the positivity rate of these individuals has not.
Dr. Howard Njoo, Canada's deputy chief public health officer, stressed that the Delta variant of COVID-19 is "already here," adding that Canadians need to "take care of our own house."
For individuals in Canada who received mixed doses of COVID-19 vaccines and are concerned about travel restrictions that they face, without getting a third dose of an mRNA vaccine, Dr. Tam said discussions around these considerations are ongoing with international partners, as data continues to be collected about safety and effectiveness of mixed doses.
"The question of additional dose and boosters are under active review and discussion right now," Dr. Tam said. "We don't really know the exact impacts of adding another dose to the existing schedules."
As Canadian provinces continue to look at loosening local COVID-19 restrictions, Dr. Tam reinforced that adding layers of protection can help to reduce to risk of a fourth wave.
"If you knew who you were interacting with and they’re all vaccinated and it’s in a small group, great, go ahead, remove your mask if everyone’s comfortable," she said. "But if you start looking at bigger gatherings and in enclosed environments, even for the vaccinated people, please consider whether there [are] safety measures in place, and wear a mask as an additional protection."