As research suggests that COVID-19 has infected about half of the Canadian population, the emergence of an even more contagious version of the virus means some people may have another round.
But questions remain about the prevalence of reinfection and the short- and long-term health impact that subsequent cases of the virus could have.
With cases on the rise, here’s what experts had to say about the emerging evidence of reinfections.
HOW LIKELY ARE REINFECTIONS?
The appearance of the Omicron variant marked the beginning of a tsunami of infections that saw the proportion of the population with antibodies against the virus increase from seven percent to 45 percent between December 2021 and May 2022, according to an analysis published by COVID. -19 from Canada. Immunity Task Force this month.
Task force co-chair Catherine Hankins said the jury is still out on the likelihood of this previously infected population contracting the virus again, particularly as Omicron’s BA.5 subvariant fuels a summer surge.
“All we know is that it can happen,” said Hankins, a professor at McGill University. “This particular variant is actually able to evade 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 rapidly but causing only mild symptoms, were not fulfilled. .
“As more evidence accumulates, it suggests that Omicron is not the great protector we all thought it would be,” he said, citing data from the UK.
Lynora Saxinger, a professor in the department of medicine at the University of Alberta, said BA.5 is different enough from earlier strains that the immunity created by a case of an older variant won’t prevent infection.
“It’s not impossible to get infected again,” he said.
HOW MUCH PROTECTION DO YOU GET FROM ‘HYBRID IMMUNITY’?
People who have been vaccinated and infected should get the “hybrid immunity” booster, Hankins said. But signs that some people are being reinfected with COVID-19 soon after a previous episode indicate any natural immune boost would be short-lived, he said.
“People really shouldn’t think it’s done and dusted. They get it, and that’s it,” Hankins said. “You’re going to get it again if you keep putting yourself out there.”
Saxinger said that BA.5 may be even more adept at getting through hybrid protection, but at this point, it’s rare for people who have had Omicron to be reinfected by one of their relatives.
“The combination of vaccination plus a relatively recent infection is not terrible against (BA.4 or BA.5), especially if you don’t have any risk factors.”
Canadian studies have shown that people with three COVID-19 vaccinations and one infection have the highest level of antibodies, Jha said.
Still, he stressed that people who have been infected may benefit from another COVID-19 vaccine.
“The evidence says very clearly that having a 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.”
HOW DOES REINFECTION AFFECT THE SEVERITY OF THE DISEASE?
Hankins said it’s hard to track whether people, on average, get sicker the second or third time they get COVID-19.
“It seems to vary a lot from person to person,” he said. “The general expectation would be that you wouldn’t be as sick the second time around, but we’re looking at everything.”
While governments report that there are large numbers of people in hospital, some of whom have had the virus before, it may seem to suggest reinfection leads to more severe illness, Saxinger said, that’s not necessarily the case. It’s just that there are more COVID cases overall.
“It’s really a function of the sheer volume of streaming where we start to see increases in serious outcomes,” he said. “But at the person level, the risk of a serious outcome still appears to be quite low, especially if you’ve had a combination of being fully vaccinated and also previously infected.”
Jha said this is another area where more study is needed.
“But in theory, I have no doubt that having multiple infections is not good for you,” he said.
“Some arrogant people say, ‘I’ll get infected a few times and then I’ll be fine,'” he added.
It’s also unclear, he said, whether reinfection increases the likelihood of getting a long-term COVID.
“There is a suggestion that multiple infections may contribute to longer duration of symptoms. But again, this is something we don’t know enough about.”
WHAT SHOULD WE DO?
“Everyone wants a quick answer and says, ‘Okay, I want to know what to do. And I want to put this behind me,'” Jha said. “But the virus works on its own schedule.”
“Our immune system is trying to keep up with a mutating virus… And basically we have to be sensible.”
The increased absorption of the third dose is key to protecting people from reinfections, he said. Each injection you receive reduces the severity of the disease.
National data shows that only 56 per cent of Canadians over the age of 12 have at least three doses of a COVID-19 vaccine, compared to about 90 per cent who have two doses.
Hankins agreed that getting a third shot is crucial.
“This is a highly infectious agent, but the more immunity you have on board, the better it is,” he said.
This report from The Canadian Press was first published on July 17, 2022.