What Canadians can expect from COVID-19 this fall and winter

With the beginning of fall and a more transmissible strain of the coronavirus than last year's taking hold, Canadians may wonder about the outlook of the pandemic over the next few months.

Some epidemiologists and infectious disease specialistsare expressing cautious optimism, hopingthat greater immunity levels just may be able to contain the delta variant that causes COVID-19, and that many jurisdictions could see hospitalization rates coming down.

"I'm always optimistic, and here's why,"said epidemiologist RaywatDeonandan, an associate professor at theUniversity of Ottawa. "Pandemics have a beginning, middle and end.And where are we right now? Locally, I think we're near the end."

Others, however, likeB.C. epidemiologist CarolineColijn, suspectCanada is still heading into a "challenging fall" despite considerable progress, particularly with vaccinations.

"The delta variant is much more infectious than the COVID that we had around last fall and even last spring," she said.

As well, provinces such as Alberta and Saskatchewan are currently in crisis mode, as a spike in COVID-19 hospitalizations among the unvaccinated has overloaded their health-care systems.

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"I have no idea how long the crisis will last," saidCraig Jenne, an infectious diseases expert at the University of Calgary.

"We may see the flattening of the curve in the coming days, but the real question is, when does that curve start to decline?"

Colder weather means people spending more time indoors, and the potential for an increase of viral transmission. Meanwhile, another delta surge or a new variant could emerge that drastically changes the outlook, some experts say.

Here is a look at the factors at play.

Where we are now

By many measures, the country is in a much stronger position facing COVID-19 than it was thistime last year.

Last fall, Canadians were still without vaccines, which wouldn't be approved until December, when Health Canada gave the green light to Pfizer-BioNTech and, weeks later, Moderna. Approval for Astra-Zeneca would follow a couple months later.

Now, according to the CBC's vaccine tracker,Canada has reached 70 per centof itstotal population and 80 per cent of itseligible population with two doses of a COVID-19 vaccine.

"Look how far we have come," Deonandan said. "We have extraordinary vaccines at supply levels that all of us here in the rich world can access.... We have a rapid test. We know so much about this disease. We have all the tools needed to control this."

All the accumulated knowledge about the virus over the past year and a half makes it slightly less unpredictable, Jenne said.

"We know what works to slow it. We know who's at risk of hospitalization. We know the impact of our public health measures."

Yet, even though there are successful vaccines and successful vaccination programs, the infectiousness of the virus means they arenot quite successful enough,Colijnsaid.

"It's so infectious that you really need almost everybody to be immunized," she said. "So where does that leave us for the outlook? What may happen is that most people who are not vaccinated will get COVID."

Hospitalizations, waning immunityand the delta variant

Deonandansaid he expects greater immunity levels will result in a drop inthehospitalization rate the proportion of infected people who become hospitalized.

Dr. ChristopherLabos, a Montreal cardiologist with a degree in epidemiology, also offered hope thatwhere vaccination rates are higher, and where most restrictions mask wearing and vaccine passportsare in place, it's going to be possible to contain the delta variant.

"And, at the very least, even if we do see cases, maybe we won't see as many people ending up in hospital," he said

One of the big unknowns, however, is the potential waning of immunity over time. Though Deonandan said he expects the ability of vaccines to protect against initial infection will gradually weaken, he predicts their protection against hospitalization and death "will remain extraordinarily good."

Based on when most Canadians received their shots, waning immunitycould start to be an issue aroundlate October, said Dr. Andrew Morris,an infectious diseases specialist at Toronto's Sinai Health and University Health Network.

And the question, he said, is whether provinces will anticipate this and offer people booster shots to try to head off the potential problem.

"If all the governments in Canada say they're going to wait to boost until we sort of see the vaccines aren't working any longer, it could kind of be a little bit too late," he said.

However, some health officials suggest another possibility that the delta variant may have peaked. That's the analysis of the U.S.-basedCOVID-19 Scenario Modelling Hub, which consists of a team of professors from across the country who provide projections about the virus.

Its modelling predicts a steady decline in COVID-19 cases in the U.S., with no significant winter surge, NPR reported.

Justin Lessler, a professor in the department of epidemiology at the University of North Carolinawho helps run the hub, told NPR that while there iswide-ranginguncertainty in the models, deaths could dropto 100 aday by March. That, he said, is dependant upon children getting vaccinated and that a more contagiousvariant doesn't emerge.

Deonandansaid it's certainly possible that some parts of the world, such as the U.K. and some U.S. states, have seen the peak of the delta wave.

"I anticipate that the northern hemisphere should see a decline in the delta waveby the end of this year," he said.

But both Deonandanand theCOVID-19 Scenario Modelling Hubalso offered a somewhat grim prediction that a decline in infection rates wouldbe due in part to the fast-spreading delta variant just running out of people to infect.

With so many delta infections among people who are unvaccinated, those who survivemight have sufficient immunity, which "starts us on that herd immunity conversation again," Deonandan said.

"A combination of sufficient coverage plus unbelievably high vaccination uptake, which we are experiencing in Canada, might mean by January we will see nomore waves," he said.

New variants?

Having said that, variants will likely continue to emerge, but whether any will become a dominant strain remains to be seen, Labos said. Much will depend on how vaccination efforts ramp up around the world.

"New variants emergebecause the virus keeps spreading," he said."It keeps copying itself. It keeps mutating. And so the more chances you give it to copy itself, the more chances you give it to have a mutation that can turn it into a different strain that's more aggressive."

Deonandan said he is a "tad concerned" that a new variant could emerge that changes factors such as the transmissibility of the virus, the profile of symptoms, and the ability to detect the virus.

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But he also pointed out that the COVID-19 vaccines have proven effective against all the coronovirus variants that have emerged so far.

"Therefore, there's no reason to expect any new variants not to be at least a little bit preventable by our vaccines, and probably preventable by ahigh amount," he said."SoI'm not overly concerned about it."

Morris views things a bit differently.

"I know that there are some experts who feel that the likelihood of a more virulent strain that's vaccine resistant is extremely unlikely to happen. But, you know, I'm willing to wait and see."