Delta COVID-19 variant: A look at the risks, symptoms and impact on vaccines

Click to play video: 'U.K. researchers say Delta variant presents new pattern of symptoms'
U.K. researchers say Delta variant presents new pattern of symptoms
WATCH: As the COVID-19 Delta variant slowly becomes to the more dominant strain globally, researchers in the United Kingdom have noticed a new pattern of symptoms for younger people. Eric Sorensen explains what's different, and whether it's a cause for concern as vaccinations ramp up – Jun 21, 2021

The more transmissible Delta COVID-19 variant has delayed reopening plans in the United Kingdom and raised concern in Canada, as cases have been identified in all 10 provinces and one territory.

The Delta variant or B.1.617.2 sub-lineage, which was first discovered in India late last year, was recently classified as a variant of concern in Canada. The first cases were detected in the country back in April and have since been rising.

While the impact of the B.1.617 variant and its sub-lineages is still being assessed in Canada, evidence from the U.K. suggests that the Delta variant spreads much more easily than other variants that have appeared in Canada so far.

As of June 15, 2021, approximately 1,187 cases of the Delta variant had been reported to the Public Health Agency of Canada (PHAC) by provinces and territories.

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Here is what we know so far about this variant of concern:


The Delta variant currently represents 91 per cent of new coronavirus cases in the U.K.

British health officials believe it is 60 per cent more transmissible than the previous dominant strain — Alpha or the B.1.1.7 variant — and scientists have warned that it could trigger a third wave of infections.

In Canada, Ontario estimates that the Delta variant will soon take over in the province and is on track to become the dominant form of the virus this summer. As of June 15, there were 497 confirmed cases of the Delta variant, according to the provincial government’s website.

Click to play video: 'B.C. health officials keep close eye on COVID Delta variant'
B.C. health officials keep close eye on COVID Delta variant

In British Columbia, 614 cases had been detected as June 5, according to the latest data by the B.C. Centre for Disease Control. As of June 14, Alberta had identified 357 cases of B.1.617 variant.

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Overall, the Delta variant accounts for the majority of the identified cases detected at the border, according to Health Canada.

“It is a concern for us,” said Levon Abrahamyan, a virologist at the University of Montreal, citing its potential faster spread.

Hospitalization and deaths

There is some evidence that the Delta variant may cause worse outcomes among those infected.

A Scottish study published in the Lancet medical journal on Monday showed that the risk of hospitalization from the Delta variant was approximately double that of the Alpha variant, especially in respondents with five or more severe medical comorbidities.

Click to play video: 'U.K. delays reopening plans as cases of Delta variant surge'
U.K. delays reopening plans as cases of Delta variant surge

New modelling released on Monday by Imperial College London suggested that the Delta variant could lead to a significant third wave of hospitalizations and deaths in the U.K.

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While early studies suggests that the Delta variant could cause “more serious disease,” the data is still accumulating on whether it leads to more hospitalizations and increases the risk of death, said Mark Poznansky, director of the Vaccine and Immunotherapy Center at Massachusetts General Hospital in Boston.

But he admitted that it does “represent a threat” especially for non-vaccinated populations.


COVID-19 illness can cause a range of symptoms from cough, shortness of breath and fever to fatigue, body aches and loss of smell or taste.

Some U.K. researchers say headaches, a sore throat and a runny nose are the most common signs associated with the Delta variant.

This observational conclusion was drawn from an app-based study.

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Tim Spector, scientific co-founder of ZOE COVID Study and professor of genetic epidemiology at King’s College London, said the Delta variant can feel “more like a bad cold” in the younger population.

“This variant seems to be working slightly differently,” he said in a June 9 video posted on YouTube.

“People might think they’ve just got some sort of seasonal cold and they still go out to parties and they might spread around to six other people.

“We think this is fuelling a lot of the problem.”

Impact on vaccines

Studies show that the current vaccines approved in Canada do offer protection against the Delta variant, but getting fully vaccinated with the two-dose regimen is especially important.

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The efficacy of COVID-19 vaccines against the Delta variant seems to be lower with a single dose but there is much greater protection with two doses, said Scott Halperin, director of the Canadian Center for Vaccinology and an infectious disease specialist at Dalhousie University.

Preliminary observational data from Scotland published in the Lancet Monday suggested that two doses of the Pfizer-BioNTech vaccine are more effective against the Delta COVID-19 variant than two doses of the AstraZeneca shot.

The same study of at 19,543 COVID-19 cases also showed that two doses of a COVID-19 vaccine among people who tested positive cut their risk of hospitalization by 70 per cent, although there were not enough hospital admissions reported to compare the vaccines.

Meanwhile, new analysis by Public Health England (PHE) showed on Monday the Pfizer-BionTech COVID-19 vaccine was 96 per cent effective against hospitalization from the Delta variant after two doses, while Oxford-AstraZeneca’s offered 92 per cent protection against hospitalization by Delta.

“These hugely important findings confirm that the vaccines offer significant protection against hospitalization from the Delta variant,” said Mary Ramsay, head of immunization at Public Health of England (PHE), in a statement.

Click to play video: 'COVID-19: Highly contagious Delta variant not dominant in Quebec'
COVID-19: Highly contagious Delta variant not dominant in Quebec

As of June 16, 16.5 per cent of eligible Canadians aged 12 and above had been fully vaccinated, data from showed.

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Given the threat, Omar Khan, professor of biomedical engineering at the University of Toronto, said there is now a greater need to ramp up the rollout for second doses in Canada.

“You need two doses to be more effective and that’s really what makes this more troublesome, especially when you think about reopening timelines and plans,” Khan told Global News.

“That’s why it’s vitally important for people to get their second dose in a timely way.”

Click to play video: 'What we know about the Foothills hospital COVID-19 Delta variant outbreaks and spread'
What we know about the Foothills hospital COVID-19 Delta variant outbreaks and spread

But the Delta variant has also shown to infect fully vaccinated Canadians.

In Calgary, out of 22 people who were diagnosed with the Delta variant linked to outbreaks at the Foothills Medical Centre last week, 11 had been fully vaccinated. Only three had not received at least one dose of vaccine, Alberta Health Services said on June 11.

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“There’s always the pressure to generate a potential booster shot to those variants,” said Poznansky.

Going forward, Abrahamyan said more research would be needed to assess the impact of the timing between two doses.

The National Advisory Committee on Immunization (NACI) has recommended a 16-week interval as the upper limit, but stressed last month that the second doses should be offered “as soon as possible”.

With an influx of vaccine supplies, most provinces have accelerated their timelines for administering the second dose.

Reopening and restrictions

Meanwhile, as COVID-19 cases continue to drop, several provinces have announced their reopening plans, allowing outdoor dining, some shopping and other limited gatherings.

But experts and health officials caution that the spread of Delta variant of COVID-19 might stall some of those big reopening plans, as was the case in the U.K.

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Abrahamyan said this would strongly depend on the percentage of the population that has been vaccinated.

As of June 16, nearly 75 per cent of the eligible Canadians had received at least a single dose of an approved COVID-19 vaccine.

Click to play video: 'Could the Delta variant derail Canada’s summer reopening plans?'
Could the Delta variant derail Canada’s summer reopening plans?

Theresa Tam, Canada’s chief public health officer, said the Delta variant should be making everyone more cautious about easing restrictions until at least 75 per cent of eligible Canadians are fully vaccinated.

“I am providing a word of caution that between now and those goalposts, we have to be as careful as we can,” she said during a news conference on June 15.

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— With files from Global News’ Leslie Young, Emerald Bensadoun, Reuters and The Canadian Press

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