Spring wave of COVID-19? Be prepared Canada, experts warn

As provinces lift COVID-19 public health measures, some experts are warning that Canada may experience another wave of infections this spring, with wastewater data in many regions showing an uptick in cases due in part to the Omicron subvariant BA.2.

Officials in Ontario, Quebec, Alberta and B.C. say wastewater analysis suggests COVID-19 infections are beginning to climb again. However, experts say it's not yet clear whether Canada's next wave will be a surge or a ripple.

Infectious disease expert Dr. Isaac Bogoch told CTV's Your Morning on Thursday that current modelling data suggests parts of Canada may experience a "bump" in cases this spring.

"It could be a wave, it could be a smaller wave… It's not entirely clear what’s on deck, but we'll probably have a rise in cases and we know that whenever there's a rise in cases, there's usually this corresponding rise, sadly, in hospitalizations and deaths," Bogoch said.

• CTV News app sign-up: Breaking news alerts and top stories delivered right to you

Public health officials tracking prevalence of COVID-19 through municipal wastewater testing in Ontario say they’re seeing a "sustained increase" in the viral signal in a variety of locations.

The increase comes after the province rolled back mask mandates and other restrictions including capacity limits for many indoor spaces and vaccine passports. Other provinces that have also recently eased restrictions, such as Alberta and B.C., are also seeing an uptick in viral load through wastewater data.

Experts say this rise is expected with the easing of public health measures, but note the simultaneous emergence of the Omicron subvariant BA.2 that's now spreading across regions in Asia and Europe is complicating matters.

While most agree that Canada's immunization rates should blunt the impacts of the so-called "stealth" subvariant, some worry that decreased public health vigilance could clear a path for BA.2 to drive up infections and hospitalizations.

In Quebec, officials say the BA.2 sub-variant of Omicron now accounts for half of new infections in the province, while Alberta Chief Medical Officer of Health Dr. Deena Hinshaw said Wednesday BA.2 is now the dominant strain of Omicron in her province.

VARIANTS AND VACCINATION

Canada's chief public health officer suggested last week that the country may be protected from the worst of the COVID-19 resurgence, instead predicting a spring "blip" as public health measures are lifted.

While evidence suggests that BA.2 is more transmissible than its Omicron predecessor, the subvariant is spreading at a relatively slow rate in Canada so far, said Dr. Theresa Tam.

It doesn't appear to cause more severe illness than other variants, she said, but international data suggests BA.2 targets people who aren't protected by vaccination or previous exposure to the Omicron variant.

• Newsletter sign-up: Get The COVID-19 Brief sent to your inbox

That means Canada's high immunization uptake should keep hospitalizations at manageable levels even if cases rise, said Tam.

However, experts say the uptake of third vaccine doses, which has shown to be crucial in protecting against severe outcomes from Omicron infection, is lagging behind first and second doses.

Dr. Brian Conway, an infectious disease expert and medical director of the Vancouver Infectious Diseases Centre, previously told CTVNews.ca that vaccination plays a major role in preventing the surfacing of new variants.

Conway said the fewer people that are fully vaccinated against COVID-19, the greater the potential for a new variant to not only emerge, but to spread.

"Variants are dependent on the virus replicating in real life, so the more susceptible hosts you have, the more virus you will have," he said. "Since it replicates so much, just by randomness, it will develop some new variants that will survive."

• What do we know about fourth doses of COVID-19 vaccines?

Bogoch said BA.2 will likely not be the last variant of COVID-19 and others will "most certainly" continue to emerge. However, he said it will be more difficult for the next variant to get a foothold in Canada because most people have immunity after being infected with Omicron, or they have been vaccinated, or a combination of both.

The "goal" is to build up that community level protection, so the next variant or wave "doesn't impact us as significantly as it has in the past," he explained.

Despite this, experts say it's important to note that vaccination is only somewhat efficient at protecting against infection, particularly when caused by the Omicron variant.

A recent study conducted in England found the efficacy of two Pfizer vaccine doses against symptomatic disease brought about by Omicron was 65.5 per cent after two to four weeks, before falling to 8.8 per cent 25 or more weeks after vaccination. With a booster dose of the Pfizer vaccine, protection increased to 67.2 per cent after two to four weeks, but also began to wane as more time went on.

Experts say this is concerning for those who are most vulnerable to severe COVID-19 outcomes, such as people who are older or immunocompromised. These groups were prioritized for early boosters in many parts of the country, thus the immunity provided by these doses are more likely to have waned in the months since. This has spurred talks of a potential fourth dose for some.

Because of this, experts say public health measures also play a critical role in protecting against infection, and some restrictions could be re-imposed in certain provinces if hospitalization rates and deaths start to surge in the coming weeks.

But Bogoch said this may be difficult given peoples' attitudes following two years of pandemic restrictions. He suggests Canadians continue to follow those measures that make themselves feel safe, such as wearing a mask and limiting social circles, despite these restrictions no longer being mandated.

"I think when we look at… the general mood, I think many people are done with COVID, but of course we know that COVID's still here, it's still around," Bogoch said. "We also know now how to keep it in check."

Just because Canada is expected to see a rise in Omicron subvariant cases similar to parts of Asia and Europe, Bogoch said this doesn't necessarily mean Canadian hospitals will be overwhelmed again.

"I think we have the tools to keep this in check. Put on your mask, get vaccinated, we can get through this," he said.

With files from The Canadian Press and CTVNews.ca writer Jennifer Ferreira