Why Canada avoided a severe winter COVID wave

This is an excerpt from Second Opinion, a weekly analysis of health and medical science news emailed to subscribers. If you haven’t subscribed, you can do that by clicking here.

Three years after the pandemic began, Canada has managed to avoid a severe COVID-19 wave this winter despite a total lack of public health restrictions, a busy indoor holiday season and a rapidly mutating virus that is still very much circulating in the population.

“We are now at a point in Canada where COVID-19 activity has reached a relatively stable state,” Canada’s chief public health officer, Dr. Theresa Tam, said at a briefing on March 10.

“While uncertainty remains about the seasonal patterns of COVID-19, the current trend suggests we may not see any major waves in the coming months.”

And new research continues to back up why: Hybrid immunity from vaccination and prior infection is holding up against hospitalizations and deaths and will likely continue to help control the severity of COVID-19 in Canada and around the world for the foreseeable future.

“We’re certainly in a much better position now than we have been at any time during the pandemic,” World Health Organization director general Tedros Adhanom Ghebreyesus said during a news conference on Friday. 

“It’s very pleasing to see that for the first time, the weekly number of reported deaths in the past four weeks has been lower than when we first used the word pandemic three years ago.”

More than 76 per cent of Canadian adults and close to 90 per cent of young adults (aged 17 to 24) are estimated to have previously had the disease as of mid-January, according to national blood donor data released by the federal government’s COVID-19 Immunity Task Force.

High levels of infection — combined with the more than 80 per cent of Canadians who’ve received at least two doses of a COVID vaccine, better treatment access and less severe infections than previous strains — have led to stronger immune protection against a virus that continues to spread globally.

“The high levels of hybrid immunity are one of the major factors explaining the contained number of COVID-19 hospitalizations and deaths this winter,” said Dr. Sara Carazo, an epidemiologist and researcher with the Quebec National Institute of Public Health.

“This is explained also by the intrinsic characteristics of new circulating variants, which were not causing a more severe disease than previous Omicron subvariants.”

But infection is not without risk — and…