Virus variants raise stakes in race against COVID-19

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The new and troubling variants of the virus that causes COVID-19 are a product of biological evolution. But scientists are warning that their emergence is a process that we are contributing to, as the virus repeatedly runs up against our biological defences and adjusts to meet the challenge.

The generally positive results from major vaccine trials this week illustrate the problem. While at least some vaccines may be good enough to thwart the new variants, they are not uniformly effective at doing so. That difference may transform what was supposed to be a decisive blow against COVID-19 into the microbial equivalent of trench warfare.

“It may be that this is going to be a longer battle over a longer period of time,” said Scott Halperin, director of the Canadian Centre for Vaccinology and a researcher at Dalhousie University in Halifax.

Dr. Halperin welcomed the results from two large-scale trials this week of vaccines developed by Johnson & Johnson and Novavax, both of which have been ordered by the federal government and are expected to become available later this year, pending authorization from Health Canada. But the fact that variants of the virus are being imported into the country far more quickly, if unintentionally, has injected more uncertainty into the race to beat back COVID-19.

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Epidemiological models forecast that the current decline in case counts across Canada could soon be overtaken by a new surge if the variants take hold. Caroline Colijn, a mathematician who specializes in infectious disease at Simon Fraser University, called the projections worrying. She added that she is no longer sure if the current state of play of the pandemic is “the beginning of the end or the beginning of a whole new beginning.”

A rapid increase in cases would strain hospitals and health resources beyond what has been experienced to date, which helps explain why Prime Minister Justin Trudeau moved this week to tighten travel restrictions. However, with 85 new variant cases now confirmed in Canada and the likelihood that scores more are connected to an Ontario long-term care facility where more than 50 people have died, it may be too little too late for some parts of the country.

One reason the variants are emerging now is that so many people have been infected worldwide. By design, a coronavirus is somewhat error prone in copying itself. That means each new infection presents an opportunity for random variations to creep into the genetic code of the virus.

Occasionally, some of those may lead to a more transmissible form of the virus. This is exacerbated when the immune system is only partly successful at blocking infection. Antibodies that are formed to intercept the virus create an obstacle course that allows only the mutants to sneak through and proliferate. These escapees then begin to outperform and dominate other versions of the virus.

Three variants of concern, linked to regional increases in cases in Britain, South Africa and Brazil, share a key mutation to the part of the virus that forms a first point of contact with human cells to initiate infection. The South African and Brazilian variants also share a second change and both have slightly different versions of a third, all of which are suspected of improving the ability of the virus to grapple onto its target.

Theodora Hatziioannou, an immunologist at Rockefeller University in New York, said she and her colleagues are seeing clear evidence in laboratory experiments that the genetic changes are being preferentially selected by previous exposure to the human immune system.

“We see these mutations arise only when you have certain antibodies in their midst,” she said.

The group reported that antibodies taken from volunteers who received the Pfizer and Moderna vaccines were less effective “by a small but significant margin” at fighting the variants. The result is broadly in keeping with what the companies themselves reported this week. One implication is that as the immunity from vaccines diminish over time, the situation may favour infection by one of the variants.

In a commentary published Thursday in the Journal of the American Medical Association, U.S. infectious-disease researchers John Moore and Paul Offit recommended investigating any case where someone who is fully vaccinated comes down with COVID-19.

Whether the variants take off in Canada or can be held in abeyance for the short term, their existence signals a new stage in the arms race against COVID-19, a race that scientists say can likely only be won with a still greater emphasis on getting vaccines to as many people as possible.

Sylvia van den Hurk, a program manager at the University of Saskatoon’s VIDO-InterVac infectious-disease lab, and a member of the federal vaccine task force, said that without the variants on the horizon it is likely that herd immunity against COVID-19 could be achieved by vaccinating 70 per cent of the population.

“This may now take a higher percentage of vaccinated people due to the variants being more fit,” she said. “It’s very difficult to predict.”

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