Vaccines may 'blunt' a 4th wave — but delta variant could surge among unvaccinated Manitobans: experts
B.1.617 variant of concern, originally detected in India, likely to hit unvaccinated pockets hard, experts say
Some experts believe a fourth wave of COVID-19 cases in Manitoba is likely to be more of a molehill than a mountain thanks to increasing rates of vaccination, but one highly contagious variant may still threaten to surge in communities with lower vaccination rates.
The number of cases associated with the B.1.617 strain — which was first identified in India — jumped from 18 on Monday to 83 on Tuesday. Those include cases of the B.1617, B.1.617.1, B.1.617.2 and B.1.617.3 variant lineages.
The B.1617.2 variant, now identified as the "delta" variant, has been designated as a variant of concern by the World Health Organization.
Though they make up a small fraction of cases in the province right now, B.1.617 variant cases have already begun to surge in parts of Ontario.
When the delta variant emerged in India, it tore through the South Asian country. Earlier this year the impact was so great that it caused widespread oxygen shortages there due to a crush of patients needing ventilators.
Dr. James Blanchard, executive director for the Centre for Global Public Health at the University of Manitoba, said the impact was felt most intensely in unvaccinated populations at that time.
The Canada Research Chair in Epidemiology and Global Public Health said given the pace of vaccinations here, and the relatively low number of delta variant cases so far, Manitoba is unlikely to see a fourth wave that rivals previous provincewide surges.
"I think that's likely to blunt the impact of the fourth wave," he said.
Manitoba's unique geographical position, along with provincial travel restrictions, helped stave off the arrival of the third wave before it hit with force in April, weeks after other provinces.
Unvaccinated pockets vulnerable
Blanchard does predict a lower, attenuated wave overall, but he says there are bound to be local surges driven by the delta variant in communities with lower vaccination rates.
"When you have a highly infectious variant like this, it'll find those pockets," he said. "We have substantial pockets, both in terms of age groups as well as regions, that aren't vaccinated, and they could have a very big impact in those populations."
As of Tuesday, nearly 67 per cent of eligible Manitobans (age 12 and up) had received at least one vaccine dose. Southern Manitoba health districts such as Stanley (14.9 per cent), Winkler (28.2 per cent) and Hanover (33 per cent) are among regions with the lowest rates.
The province hopes to have 70 per cent of the population fully vaccinated by the end of next month. That second dose may determine the size of the next surge, said Dr. Prabhat Jha.
"It's basically a race between ... effective vaccination coverage and the variant that's occurring right throughout Canada and the U.K.," said Jha, a professor of global health at the University of Toronto and a scientist at Unity Health Toronto.
There are early signs that a single dose of a two-dose vaccine, while offering fairly robust protection against other strains of the coronavirus that causes COVID-19, may only be about 33 per cent effective against the delta variant.
"People should be assured that if most of the population has at least one dose and important groups have two doses, we won't necessarily see a resurgence," said Jha. "All the evidence suggests it does respond to vaccines, but the key goal is to stay ahead of it."
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If the delta variant begins to take off in Manitoba, it may warrant expediting the second dose campaign in select priority groups, he said.
Jha said another complicating factor is that B.1.617 and its subtypes can't presently be identified through most COVID-19 screening processes, so samples have to be sent to the National Microbiology Lab for sequencing.
However, there could soon be some innovations that enable local labs to confidently identify the variant without shipping vials off to national labs, he said.
Shortening window between doses
Carlos Farkas, a post-doctoral researcher at the University of Manitoba's Rady Faculty of Medicine and CancerCare Manitoba, has studied variants. He thinks a fourth wave of some sort is coming, though it will be smaller.
"The rate of vaccinations here is good, but it's not enough, I think, to stop a fourth wave," Farkas said.
He thinks Manitoba should consider shortening the window between first and second doses now.
"We will see rises in cases for sure, I can assure you, if they will not shorten the window."
Farkas predicts Manitoba's fourth wave curve could begin to take shape this summer.
He thinks as Manitoba considers gradually easing some restrictions, it shouldn't permit gatherings of greater than five people.
"People need to see each other, their loved ones, but in terms of gathering outside [in groups of strangers], I think it's still dangerous," he said.
'This thing can explode'
Dr. Anand Kumar said he's confident Manitoba could see a significant fourth wave if the province lifts too many restrictions soon due to B.1.617.
"We're going to be very careful with that," said Kumar, an infectious disease expert and intensive care unit physician at Health Sciences Centre in Winnipeg.
"This thing can explode very quickly. If we use the same criteria for reopening as we did before, we're going to have a big problem on our hands, I think, within a few months."
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With files from Susan Magas