Rees Kassen is a professor of evolutionary biology at the University of Ottawa. Murray Baron is a professor of medicine at McGill University.
Pandemic restrictions are easing across the country, and last week brought multiple announcements from the federal government about additional vaccine supply. It’s been enough to make some people wonder: Could we be coming out of the dark and into the dawn with COVID-19?
But the race is far from over. Cases attributable to the “variants of concern” (VOCs) have already swept through countries such as Britain, South Africa and Brazil. The P.1 variant from Brazil is particularly worrisome, as it arose in the city of Manaus, where rates of population immunity from the original variant were already high. Now the ones first reported in Britain and South Africa are on the rise here in Canada, and no doubt the one reported in Brazil is not far behind.
From a public health and evolutionary perspective, we see this as cause for alarm on two fronts.
The first is the fact that the VOCs are so much more transmissible – from 40 to 50 per cent higher – than the currently circulating versions. As alarming as this is on its own, let’s put it into some perspective using the lockdown Canadians just experienced in January.
Data from Ontario show that it succeeded in bringing the virus’s basic reproductive number (R0) – the key metric describing the number of new infections caused by a single infected individual – down to somewhere between 0.7 and 0.8. Remember that when R0 is less than one, the virus cannot spread. In short, the lockdown worked.
But imagine a VOC is the predominant strain circulating, and it has an increase in transmissibility on the lower end, say 40 per cent, of the range given above. R0 would now be at least 1, which is not low enough to get rid of the virus. Any leakage during lockdown would mean R0 creeps above 1. We’d be back to exponential spread of the virus in the community despite being under the most restrictive public health measures we’ve yet experienced.
The only real solution to get the virus under control is to vaccinate as many people as we can, as quickly as we can. But the rolling seven-day average of vaccines being administered each day in Canada is just two for every 1,000 people, compared with Israel’s 10 and the U.S.’s six.
Which leads to the second reason for concern: The longer it takes for us to get the virus under control, the more time it has to mutate and generate potentially new, more worrisome variants. Particularly concerning are “escape mutants,” which can evade detection by our immune system.
Evolution is not working in our favour here. The number of viruses is so large that even a rare event like a mutation giving one virus variant some advantage over another is likely to occur. There is a good chance that the variants we are seeing now are just the tip of the evolutionary iceberg.
We are racing against what evolutionary biologists call a “Red Queen” dynamic, named after the character from Lewis Carroll’s Through the Looking-Glass who says that “it takes all the running you can do, to keep in the same place.” We are running now just to stay ahead of the virus and its new variants.
So, how can we best do that? We have no control over the mutation rate of a virus, and at this point we can’t reduce the population size of the virus itself. We can keep it from growing and keep new variants from spreading using physical-distancing measures and lockdowns – though as we all know, these are blunt instruments.
But until we can get the vaccine widely delivered, that’s the best recourse we have. The presence of variants such as P.1, which may not be affected by immunity from previous infection or our current vaccines, should be responded to as if it’s a new pandemic. Not only should we stop opening up now, we probably need even stricter measures to prevent the spread of VOCs. We may even have to go back to square one.
Vaccination is the other arrow in our quiver. But time is of the essence, as a recent analysis by Ontario’s COVID-19 Science Advisory Table shows. If Ontario had delivered the vaccines to all residents of long-term care homes just two weeks earlier than it had, 600 COVID-19 cases and more than 100 deaths by the end of March could have potentially been prevented.
When you’re in a race with a virus, every single day matters. How we navigate the next few weeks will determine which will win.
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