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Thousands of Canadians have recovered from COVID-19. Do they need the vaccine?

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Nearly 400,000 Canadians who contracted COVID-19 have recovered — and that’s just those officially reported.

While there is a growing body of research that suggests antibodies can be present for months after infection, experts agree it’s still important to get the vaccine.

“Just because you got infected, doesn’t mean you’re immune,” said Raywat Deonandan, an epidemiologist with the University of Ottawa.

“What does it gain us if people who have been infected and recovered do not seek the vaccine? Not much.”

What about immunity following illness? 

When you catch COVID-19, your body makes antibodies that find and destroy the virus in your system. This leaves you with COVID-19-specific antibodies and immune cells that can fight off the infection.

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These antibodies can protect you from catching it again, but for how long? That, experts say, is not yet known.

Read more: How long does coronavirus immunity last? Some studies suggest months

The current thinking is that antibody levels start to wane after a few months, particularly in milder or asymptomatic cases. But there’s no way to know for sure, said Deonandan.

“There is a whole range of different immunogenic responses. Some people with mild symptoms produce very few antibodies if any. Some people with high symptoms produce a lot of antibodies,” he said.

In other words, it’s not cut and dry.

“The range is much greater than you would get in a vaccine, which is calibrated specifically for optimum immunogenic response.”

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Studies on the topic range, too. Some suggest protection by natural immunity can persist for years, preventing serious illness, if not reinfection. Others point to that protection waning rapidly — far faster than previously thought.

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Once that immunity fades, you could be at risk for catching COVID-19 a second time, Deonandan said.

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“While it’s not the norm, it does exist and it can happen,” he said.

There have been credible cases of reinfection around the world since the onset of the pandemic. In most of these cases, a second bout with the virus produced milder symptoms or none at all. But for several — including one in Ecuador — the illness was more severe the second time around. In the Netherlands, an 89-year-old woman died during her second illness.

Read more: Cases of coronavirus reinfection raise concerns over immunity

Rare as these cases may be, they prove that reinfection is possible, said Isaac Bogoch, an infectious disease specialist based out of Toronto General Hospital.

“In fact, it’s likely that [there] is a gross underrepresentation of the number of people that have been reinfected,” he said.

Consider the vaccine as a booster, said Deonandan. Even if your antibodies are strong, or you recovered from the virus very recently and are next in line to get the shot, the vaccine is only going to “improve your immunogenic response.”

“There is precedence for this. I’m over 50, I got my shingles shot two years ago, but I had chickenpox,” he said.

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“You would think you wouldn’t need it if you had chickenpox, but your immunity does wane. So there’s nothing to be lost and a whole lot to be gained from getting that booster shot.”

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Can I afford to wait?

While some believe those who have recovered from COVID-19 could be among the later groups of people to get vaccinated, experts say it’s generally better if everyone gets the shot when it’s their turn.

An advisory panel for the U.S. Centers for Disease Control and Prevention (CDC) considered this scenario while reviewing Pfizer’s trial data before approving the vaccine. It suggested some people could afford to wait a little longer to get the shots if they had the virus.

Health-care workers who had COVID-19, for example, might want to let their colleagues go ahead of them, the panel suggested, since the chance of reinfection is low for the first few months.

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This could be applied once vaccination rolls out more widely too, said Deonandan.

“If you know you had COVID-19 recently and you’re not a high-risk group and one day you see a big line up to get the vaccine, I can understand deciding to wait a few days,” he said.

“If you want to self-deprioritize when it’s open to the masses, that’s perfectly reasonable, but that’s not the same thing as saying you don’t need it.”

Read more: Canada begins coronavirus vaccine rollout. Here are the provinces’ plans

This type of system wouldn’t work on a larger scale, however, added Bogoch, nor would it be advisable.

“In a world with infinite resources we could theoretically identify people who have recovered from the infection and say, ‘OK, you’re going to come in one or two months later than anyone else.’ Sure, that would help, but the logistics of setting something up like that … I don’t see a lot of gains,” he said.

Even then, it won’t do much to get us closer to herd immunity, added Deonandan.

“About 390,000 people have recovered from COVID-19. As a fraction of all the people who need to get the vaccine — 27 million approximately for 70 per cent herd immunity — that’s tiny,” he said, looking at Canada case numbers and population.

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Bogoch put it simply: “If it’s your turn to get the vaccine, get the vaccine.”

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Is it safe to get vaccinated after having COVID-19?

Getting the vaccine after having had COVID-19 is both safe and beneficial, the experts agree.

In fact, a number of participants in clinical trials for the vaccines had been infected with the virus without knowing it. People with prior COVID-19 diagnoses weren’t allowed to volunteer for the vaccine tests, but there was no screening to rule out people who might have been previously infected and not known it.

So some symptom-free infections might have been included. The CDC panel said there was no need to test for those silent infections before administering the vaccine. Their immune responses to the vaccine would still have been analyzed.

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It goes back to considering it as a booster, said Deonandan.

“Consider your infection your first immunity shot. That booster is going to improve it,” he said.

“There’s nothing to be lost from this.”

–With files from the Associated Press and Reuters