With research showing that COVID-19 has infected roughly half of Canada’s population, the emergence of an even more contagious version of the virus means that some people may be in for a new round.
But questions remain about the spread of reinfection and the short- and long-term health effects that subsequent cases of the virus can have.
As cases mount, here’s what experts have to say about the emerging evidence of reinfections.
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How likely are re-infections?
The emergence of the Omicron variant set off a tsunami of infections that saw the proportion of the population with antibodies to the virus rise from seven per cent to 45 per cent between December 2021 and May 2022, according to an analysis released by the Canadian COVID-19 Task Force for immunity this month.
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The co-chair of the task force, Kathryn Hankins, said the jury is still out on how likely this previously infected population is to catch the virus again, especially as Omicron’s BA.5 subvariant fueled a summer surge.
“All we know is that it can happen,” said Hankins, a professor at McGill University. “This particular variant is indeed capable of evading immunity, including immunity to its previous… sub-variant.”
Prabhat Jha, a professor of epidemiology at the University of Toronto’s Dalla Lana School of Public Health, said early hopes that Omicron would act as a “benign natural booster,” spreading quickly but causing only mild symptoms, have not been borne out.
“As more evidence accumulates, it suggests that Omicron is not the great defender that we all thought it would be,” he said, citing UK data
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Linora Saxinger, a professor in the Department of Medicine at the University of Alberta, said BA.5 is different enough from previous strains that immunity built up from a case of an earlier variant may not prevent infection.
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“It’s not impossible to get infected again,” she said.
How much protection do you get from ‘hybrid immunity’?
People who are both vaccinated and infected should be supported by “hybrid immunity,” Hankins said. But signs that some people are re-infected with COVID-19 shortly after a previous attack suggest that any natural boost to the immune system would be short-lived, she said.
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“People really shouldn’t think it’s done and washed. They get it and that’s it,” Hankins said. “You’ll get it again if you keep putting yourself out there.”
Saxinger said BA.5 might be even more adept at breaking through hybrid defenses, but at this point it was unusual for people who had Omicron to be re-infected by one of its kin.
“The combination of vaccination plus relatively recent infection? not terrible against (BA.4 or BA.5,) especially if you have no risk factors.’
Canadian studies show that people with three COVID-19 vaccines and one infection have the highest levels of antibodies, Jha said.
Still, he stressed that people who have been infected may benefit from another vaccine against COVID-19.
“The evidence is very clear that relying on natural infection to protect you is really risky. We knew that from the beginning,” he said. “The best protection is at least three doses of the vaccine.”
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How does re-infection affect disease severity?
Hankins said it’s difficult to track whether people, on average, get sick the second or third time they contract COVID-19.
“It seems to vary a lot from person to person,” she said. “The general expectation would be that you wouldn’t be as sick the second time, but we see everything.”
While governments report large numbers of people in hospital _ some of whom have had the virus before _ they may seem to suggest that re-infection leads to more serious illness, Saxinger said, that’s not necessarily the case. It’s just that there are more cases of COVID in general.
“It’s really just a function of the sheer volume of transmission where we’re starting to see increases in hard scores,” she said. “But at the human level, the risk of a severe outcome still seems quite low, especially if you’ve had a combination of full vaccination and also previous exposure.”
Jha said this is another area where more research is needed.
“But in theory I have no doubt that having multiple infections is not good for you,” he said.
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“Some cavaliers say, ‘I’ll just get infected a few times and then I’ll be fine,'” he added.
It’s also unclear, he said, whether re-infection increases that likelihood of long-lasting COVID.
“It has been suggested that multiple infections may contribute to longer-lasting symptoms. But again, this is something we don’t know enough about.
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What should we do?
“Everybody wants a quick answer and says, ‘Okay, I want to know what to do.’ And I want to put that behind me,” Jha said. “But the virus works on its own schedule.”
“Our immune system is trying to deal with the mutating virus … And we have to be smart.”
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Increasing the intake of a third dose is key to protecting people from re-infections, he said. Each injection you receive reduces the severity of the disease.
National data show that only 56 per cent of Canadians aged 12 and over have had at least three doses of the COVID-19 vaccine, compared to roughly 90 per cent who have had two doses.
Hankins agreed that getting a third shot was critical.
“It’s a highly infectious agent, but the more immunity you have on board, the better,” she said.
© 2022 The Canadian Press
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