Highly contagious delta variant could be Alberta's primary strain by late June, scientists warn

Whenthe alpha variant of coronavirus first began to spread in Alberta early this year, GosiaGasperowiczsounded the alarm that the province was headed for a third wave which would likely be worse than the previous two.

Now, she and other experts are warningthe delta variant could take over as Alberta's dominant strain by the end of June potentially bringing a fourth wave of COVID-19 cases in the fall, unlessaction is taken.

"Beginning of March it was super clear, and still it was downplayed but it was really clear that we [were] heading to the third wave and similarly now it is very clear that we are going to the fourth wave,"the developmental biologist with the University of Calgary said.

A total of 344 cases of the delta variant have been identified in Alberta, an increase of 82 cases since Friday. Nearly all of those cases are in Calgary.

Variants account for about 76 per cent of Alberta's 3,000 active cases, which are down by 20,000 in the last month. Most of those cases are the alpha variant.

• Delta variant worries grow in Alberta as rollout of 2nd COVID vaccine doses accelerates

Gasperowicz said delta variant casesaredoubling roughly every six to12 days. With a doubling time of eight days, she said delta will become the dominant strain around June 26. If it doubles at a more conservative prediction of every 12 days, the variant would become the dominant strain around July 5.

"We are in exponential [growth] now," she said."It's the same story."

In a worst case scenario that couldmeandaily case counts once again in the thousands a projection that doesn't factor in thefuture negative effects of loosened restrictions,or the positive effects of higher vaccination rates,Gasperowicz said.

Dr. James Talbot, co-chair of the Edmonton zone medical staff association's strategic COVID committee and a formerchief medical officer of health for Alberta, said he has increasingly been feeling a sense of deja vu.

Hethinks reopening before the province hits 70 per cent of people fully immunized not just with one dose, the current benchmark is a mistake.

"What we're looking at is the potential for a fourth wave to complicate what happens in September with trying to get kids into school and people back to work," he said.

Studies out of the United Kingdom, where the delta variant has driven a surge of new cases, show only about a third of people are protected against symptomatic cases of the variant after a single shot.

Both AstraZeneca and mRNA vaccines are estimated to be 92 to 96 per cent effective against hospitalization after two doses.

2 doses needed

Talbot said it's important to remember that right nowno children under 12 are vaccinated and the majority of those vaccinated only have one dose, so are largely unprotected from the delta variant.

"Pushing for the 70 percent of [one dose]is giving people a false sense that that's the end, that after that everything is fine," he said.

"If you get in the 70 to 80 per cent range with people who are protected [with two doses], you can protect even those who haven't gotten the vaccine. That's literally what herd immunity means."

He said the greater the number ofinfected people, the greater the risk of the virus mutating intomore infectious or deadly variants.

Talbot said he'd like to see the province move more cautiously, and be more transparent in sharing its internal modelling on variant transmission.

WATCH |COVID-19 vaccines can help Canada beat delta variant, experts say:

COVID-19 vaccines can help Canada beat delta variant, experts say

3 years ago

Duration 3:34

The U.K. has delayed further reopening because of a spike in the delta coronavirus variant, but experts say Canada can prevent the same thing with a push on COVID-19 vaccines including second doses.

Chief Medical Officer of Health Dr. Deena Hinshaw acknowledged concerns over variants during a press conference last week, as she announced expanded eligibility for second doses of vaccine.

"As we continue to face COVID-19 and its emerging variants, the sooner we can get everyone fully immunized, the better," Hinshaw said.

"I have stressed for months that one dose of the vaccine provides good protection and it does. The evidence that we are seeing in Alberta, however, shows a significant jump in effectiveness after receiving the second dose."

Dr. Alain Tremblay, a professor of medicine at the University of Calgary and respirologist at Foothills hospital, said it's worth noting that exponential growth curves look flatat first.

"That's what they saw in the U.K. even the U.K. variant is not the U.K. variant anymore," he said. "[Delta] clearly has more staying power than the alpha [variant] ... the question is, is it going to replace it and we stay at 100 cases per day, or is it going to replace it and we're gonna have another wave."

Tremblay said he was fairly comfortable with earlier stages of reopening, but as Alberta prepares to lift all restrictions, he's worried.

"I'm really concerned what we're going to do July 1," he said. "Are we going to be extremely aggressive with contact tracing? Or are we just going to say oh, it's phase three, we're not doing anything. And really there's been no clarity on that, not that I've seen."

Dr. Andr Corriveau, Alberta's deputy chief medical officer of health, said Tuesday that as overall cases decrease, more transmissible variants will become predominant by default.

"We're watching and certainly trying to do all we can still with the public health measures in place to contain it in the Calgary area we are still confident that our strategy is aimed in the right way to get as many Albertans immunized as possible as soon as possible," he said.

Corriveau said modelling to predict case growth of the delta variant in Alberta is underway, but it hasn't been completed yet. He added that he does not have precise details about what measures will remain in place to combattransmission as the province reopens.

Gasperowiczsaid the fourth wave mayalready be growing it's just that the delta case growth isn't obvious due to overall case decline.

"It's already here, it's just invisible."