Why omicron is overtaking delta — and what that means for our fight against COVID-19

In the battle of the variants, omicron is poised to win. While delta has long dominated the bulk of Canada's coronavirus cases, the latest variant of concern is set to overtake other variants both here and abroad as it spreads through more than 60 countries around the world.

Ontario figures suggest new variant has doubling time of just 3 days

Early evidence suggests omicron is more adept at infecting people who’ve already had COVID-19 or multiple doses of leading vaccines. In this photo, people walk along a busy street, wearing masks meant to prevent spread of the virus. (Ben Nelms/CBC)

In the battle of the variants, omicron is poised to win.

While delta has long dominated the bulk of Canada's coronavirus cases, the latest variant of concern is set to overtake other variants both here and abroad as it spreads through more than 60 countries around the world. 

Early evidence suggests omicron is more adept at infecting people who've already had COVID-19 or multiple doses of leading vaccines, and the heavily mutated variant also has an uncanny knack for transmitting between people in the same home. 

In other words, it's likely incredibly contagious, and capable of leaving delta in its dust. 

While there are hopeful signals that vaccination still protects against serious disease, with boosters offering a stronger shield against any level of omicron infection, multiple medical experts who spoke to CBC News warn it's time to buckle down for a tough stretch ahead — since this variant will find its way to the vulnerable, even if most Canadians who get infected are largely unscathed. 

"I don't think we've seen anything like omicron in this pandemic yet," said Sarah Otto, an expert in modelling and evolutionary biology with the University of British Columbia in Vancouver. "It's capable of taking over in a matter of a few weeks."

U.K. bracing for 'tidal wave' of cases

In the U.K., where omicron is on track to take over as case counts keep rising, top medical officials said Sunday that data on severity of these infections isn't yet clear, but hospitalizations tied to omicron are already happening.

A day later, the country reported its first omicron-linked death, as Prime Minister Boris Johnson warned of a "tidal wave" of cases.

WATCH | U.K. Prime Minister Boris Johnson notes the 'sheer pace' of omicron spread:

Britain sees first death with Omicron coronavirus variant

2 years ago
Duration 3:41
British Prime Minister Boris Johnson warned that a 'tidal wave' of omicron coronavirus infections is coming and urged everyone to get a booster shot after the first person in the United Kingdom died of the variant. (Kirsty O'Connor/The Associated Press)

The variant is also surging in Denmark, while French hospital officials are warning of an omicron-fuelled wave next month.

The latest federal modelling data in Canada suggests countrywide coronavirus cases here could quadruple to 12,000 a day in January if "omicron successfully establishes." 

And the most up-to-date figures provided by Ontario's science table show omicron has a reproduction number roughly three times that of delta — and a doubling time for cases of only three days — with the variant already making up an estimated 31 per cent of that province's coronavirus cases as of Monday.

Just one day prior, omicron made up an estimated 20 per cent of reported cases.

WATCH | When could omicron become dominant in Canada?

COVID-19: When could omicron become dominant in Canada?

2 years ago
Duration 6:56
Andrew Chang talks to infectious diseases specialists Dr. Susy Hota and Dr. Lisa Barrett about when the omicron variant may become dominant in Canada, whether it appears milder than delta and if people should change their holiday plans.

In South Africa, the country which alerted the world to omicron's existence, it only took two weeks for omicron to out-compete delta as the dominant variant in genomically sequenced samples, said Jody Boffa, a Canadian epidemiologist currently working as a research fellow at Stellenbosch University in Cape Town.

It's not yet clear what Canada's exact experience will be, given the differences in vaccination rollouts, timelines, and vaccines used in different countries and our overall two-dose vaccination rate — which is far higher than many countries' around the world at more than three-quarters of the population, with boosters now rolling out as well. 

Vaccination differences aside, even a less virulent variant transmitting this quickly "would result in many more absolute hospitalizations and deaths in a short span of time," Boffa said in an email exchange with CBC News.

Questions remain over disease severity

The concern over omicron's expected dominance has less to do with its impact on individuals — given how many Canadians are still somewhat protected by one, two or even three vaccine doses — and more on what happens when it finds its way to those at higher risk of serious infections, including anyone unvaccinated, older or immunocompromised.

The usual COVID-19 numbers game, several epidemiologists agreed, means a fast-spreading, more-contagious variant could again put pressure on hospital systems.

"If it is not severe in everybody, we are lucky. But we don't know if that's true," said Otto. "If it's even half as severe among the unvaccinated, that's still too severe. So skyrocketing among unvaccinated cases means more exposed hospitals overrun in mid-January."

Early proclamations of mild disease have given way to a collective pause, as medical experts warn that more time and data are needed to understand the true picture of how omicron infections progress.

WATCH | Data on severity of omicron variant still preliminary, but Tam urges caution:

Data on severity of omicron variant still preliminary, but Dr. Tam urges caution

2 years ago
Duration 1:20
Chief Public Health Officer Dr. Teresa Tam says the data on the severity of the omicron variant is still premature but that Canadians should still exercise caution.

South Africa hasn't yet seen a surge in severe illness or deaths roughly a month into its omicron experience, though it's important to note the country has a relatively younger, lower-risk population.

One preprint case study published online on Friday, which has not yet been peer-reviewed, looked at one cluster of omicron infections among a group of young-adult Germans staying in the country. 

The seven individuals each had three doses of COVID-19 vaccines, yet developed mild symptoms — including a runny nose, sore throat, shortness of breath, and for all of them, a dry cough — echoing broader evidence that this variant can evade some level of vaccine-based immunity. 

A line in the preprint case held promising news: "This suggests that full vaccination followed by a booster dose still provides good protection against severe COVID-19."

But will the potential for milder infection hold true as this variant spreads more to older adults, particularly those who aren't yet vaccinated or have pre-existing health issues? 

"I really want to emphasize [that] we do not know it's milder for everybody," said Otto.

Protect community through 'individual actions'

Given the uncertainty over omicron's severity, and the mounting evidence that it can spread through both unvaccinated and vaccinated populations, it may be time to brace for the worst, even as the world hopes for the best.

One Canadian modelling expert — speaking on background due to their role with a federal advisory body — noted early data from Ontario shows the province was already in a period of exponential growth, even without omicron in the mix. 

"Once it becomes more established here, we're going to very quickly have an overwhelmed health-care system," they said in an email to CBC News. "Vaccinations are coming online too slowly to markedly change that trajectory, and beyond hoping for boosters to save us, we're not doing anything."

While most of the serious COVID-19 infections would likely be among the unvaccinated, as seen throughout the pandemic, enough breakthrough cases tied to a more contagious variant could mean a rising number of serious infections among vaccinated Canadians as well — if the virus has the opportunity to spread.

As millions of families are set to gather for the holidays, and as most Canadians continue going about their daily lives with few public health restrictions to dissuade them, Otto stressed there's a renewed need to maintain basic precautions, even if you're vaccinated. 

"We protect our community by all of our individual actions," she said.


Lauren Pelley

Senior Health & Medical Reporter

Lauren Pelley covers health and medical science for CBC News, including the global spread of infectious diseases, Canadian health policy, pandemic preparedness, and the crucial intersection between human health and climate change. Two-time RNAO Media Award winner for in-depth health reporting in 2020 and 2022. Contact her at:

Add some “good” to your morning and evening.

A variety of newsletters you'll love, delivered straight to you.

Sign up now