Early signs suggest fall COVID-19 wave starting in Canada

There are early signals Canada is already entering a fall COVID-19 wave, while updated booster shots likely remain weeks away.

Earlier this week, the Public Health Agency of Canada said fluctuations in virus activity across the country could be an “early sign” of increased infections. 

The percentage of COVID tests coming back positive, for example, had been gradually declining since the spring, but started going up again over the last month — most recently hitting nearly nine per cent. Hospitalizations increased in August as well, jumping roughly 11 per cent in a week, as the number of hospital beds occupied by COVID patients hit more than 1,700 by Aug. 15.

Cross-Canada wastewater signals are also rising. By late July, at least seven of the 39 sites tracked by federal officials had reported an increase, and that number has nearly doubled since then to at least 13.

Western University microbiologist Eric Arts said Ontario’s wastewater in particular is showing an increase in virus samples, but with reduced reporting and limited testing across much of the country, the full picture is hazy. What is clear, Arts added, is that caseloads in the U.S. are already going up “dramatically,” meaning Canada’s wave may not be far behind.

“Everyone’s hearing, myself included, anecdotal evidence of new infections of people that we know,” he said.

Waning immunity, new subvariant may play role

How big Canada’s fall surge becomes will largely hinge on the country’s level of population immunity, experts say, as well as the timing of fall booster shots that aren’t yet approved in either Canada or the U.S. 

“We’re having up-and-down wobbling of our COVID numbers as we balance out transmission with immunity,” said researcher and epidemiologist Caroline Colijn, a Canada 150 Research Chair in Mathematics for Evolution, Infection and Public Health at Simon Fraser University.

As CBC News recently reported, research shows a majority of the population has developed some level of immunity against SARS-CoV-2, thanks to high rates of vaccination and three-quarters of Canadians likely having detectable antibodies linked to prior infections. Hybrid immunity — developed through a combination of both prior vaccination and infection — is thought to be a particularly robust form of protection.

But while many individuals’ immune systems are now better trained to recognize this threat, reducing rates of serious illness and death over the course of the pandemic, the level of protection needed to avoid another infection in the first place can fade over time.

“We haven’t had a large COVID wave in the summer, and we haven’t had a lot of vaccinations. So that protection against infection might have waned to some extent,” said Colijn. “And that puts us in a position for potentially a larger wave.”
A contagious subvariant called EG.5 that’s circulating widely right now could also help fuel a surge, though scientists are still assessing the risks posed by the Omicron offshoot.

Early evidence suggests it’s no more severe, yet it does appear better able to evade front-line immune defences, allowing it to infect — and re-infect — more people.

There’s no cause for panic, Colijn stressed. But among people that may not have an infection or booster shot in months, a fast-spreading subvariant can find plenty of new hosts.

“You don’t need a lot more severity to cause a large problem if you have a lot more numbers,” she warned.