As Omicron reveals itself, Canada’s scientists scramble to predict its impact on at-risk populations

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It’s no one’s idea of an early Christmas present, but what Anne-Claude Gingras wants most right now is a good batch of Omicron variant proteins.

They may come from samples of the COVID-19 variant that were obtained and cultured from Canadian cases of Omicron. Or they may be synthesized from scratch using an RNA blueprint that mimics Omicron’s genetic sequence – now available to researchers worldwide.

Either way, once Dr. Gingras has the proteins in hand her goal is to combine them with blood samples drawn from Ontario residents in long-term care who have received their third dose of a COVID-19 vaccine.

“It’s the same cohort we’ve been profiling against Alpha, Beta, Gamma and Delta,” said Dr. Gingras, a senior investigator at Mount Sinai Hospital in Toronto. “We want to make sure we can provide some guidance to this supervulnerable population.”

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Evidence from countries where Omicron is spreading, especially South Africa, suggest that it is better at evading vaccines than previous variants of concern and will produce more breakthrough infections.

A priority for Dr. Gingras and her colleagues is to see whether she can replicate the laboratory findings reported on Wednesday by Pfizer and BioNTech that show the companies’ vaccine still holds up against Omicron in individuals who have received a booster shot.

If this proves not to be the case for those at elevated risk, long-term care facilities may require more stringent measures to thwart outbreaks, including increased rapid testing and restrictions on visitor numbers.

“There’s a list of things that we need to be thinking about in long-term care,” said Allison McGeer, a physician and infectious-diseases researcher who co-leads the cohort study at Mount Sinai. “Some we may want to start doing now to minimize the damage. And some we want to be ready to turn on the moment we recognize we need them.”

Ultimately, Omicron may accelerate the need for fourth doses for long-term care residents and possibly antiviral medications as a preventive measure, Dr. McGeer said. Meanwhile, the impact of Omicron on the broader population remains harder to discern.

The latest technical report on COVID-19 variants from Britain’s health agency projects that Omicron cases there will reach parity with cases caused by the preceding Delta variant later this month. In Canada, modelling studies presented on Friday by Chief Officer of Public Health Theresa Tam show the potential for a steep spike in cases in mid-January if Omicron becomes established.

Such a spike would be exacerbated by the variant’s improved ability to move among the vaccinated and produce infections at a higher rate. In doing so, it would more easily find the remaining population that is unvaccinated and entirely susceptible. A too-sudden acceleration of COVID-19 in that group alone would be enough to strain Canadian emergency rooms to the breaking point, epidemiologists warn.

The silver lining may lie in indications in the South African data that Omicron is producing a less severe form of the disease in many who contract it. Although results are preliminary, it is a point that many experts have remarked on, including Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases and White House chief medical adviser.

Dr. McGeer said there are several important differences that make it difficult to extrapolate the South African data to predict the impact of Omicron in Canada.

For starters, South Africa’s population is younger, which lowers the chance of severe COVID-19 on average. The country also had a much higher infection rate during previous waves of the pandemic, including a second wave dominated by the Beta variant, which shares some of Omicron’s mutations. That variant had little impact in Canada because of the overwhelming prevalence of the Alpha and Delta variants.

In comparison, it’s possible that Canada is not as well braced for a variant with Omicron’s particular characteristics despite a higher vaccination rate. And even if Omicron continues to exhibit less disease severity per individual case, that benefit can be outweighed by a larger total case count.

A more speculative question is how Omicron may change the nature of the pandemic in Canada after its initial wave has crested.

Jane Heffernan, a mathematical epidemiologist at York University in Toronto, said that if Omicron proves to be more transmissible but less severe, it could hasten COVID-19′s transition to an endemic disease. Over time it would begin to resemble seasonal flu or – in a best-case scenario – the more benign coronaviruses that are associated with the common cold. Such a future fits with the evolutionary principle that viruses benefit when they can infect individuals easily but not prevent people from circulating among others and spreading the virus further.

Sarah Otto, a theoretical biologist at the University of British Columbia, cautioned that this reasoning may not apply to COVID-19, a disease in which severe outcomes and death tend to come long after the virus has had an opportunity to spread to others.

However, Dr. Otto said, there is another way to look at why the variant may have lower severity.

Earlier variants are thought to have arisen in immunocompromised individuals, where mutations helped them flourish and defeat a weakened immune system. If the same process gave rise to Omicron, which has many more mutations than other variants of concern, it may have carried on evolving in a single host for months in order to accumulate so many changes. But that would only be possible if the host were able to live with the virus rather than succumb to it.

“We have to think about what this variant was selected to do inside somebody for six months or a year,” Dr. Otto said. “If it had been very severe, that individual might not have survived long enough to pass it on.”

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