Scientists say COVID-19 booster intake is waning, urge Canadians to book their shots

By Avis Favaro and Alexandra Mae Jones

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    TORONTO (CTV Network) — Across Canada, there have been booster clinics and vaccine days, all to get more Canadians their shots — but recently, the drive to get shots into arms has hit a curb.

Health officials say they’ve been noticing enthusiasm waning.

“I think we’re all concerned with the drop,” Nicole Dupuis, CEO of Windsor-Essex County Health Unit, told CTV News. “We still have quite a number of individuals who have still not received a second dose.”

And although the advent of Omicron spurred regions to open up booster shots to more ages, the rate of Canadians getting booster shots has gone down.

So far, about 30 million Canadians are double-vaccinated.

As of the most recent data, only 15 million third doses have been given out.

“To get the best bang for your buck, you really should be getting the booster,” Mina Tadrous, an assistant professor at the University of Toronto, told CTV News.

A new study conducted in Canada offers real world evidence that three shots offer the strongest protection, scientists say.

Researchers tracked data on over 20,000 people who were confirmed by PCR test to have contracted COVID-19 as Omicron slammed into Ontario in December. The study has been submitted for peer-review.

The study found that six months after having received two doses, there was very little protection left to prevent symptomatic illness from the Omicron variant.

That third dose, however cut the chance of illness with symptoms by 61 per cent.

This doesn’t mean that two doses provided no protection at all — when it came to protecting against hospital admissions and death from Omicron, two doses cut the risk by 82 per cent, the study found.

But that third dose reduced the risk of hospitalization and death by 95 per cent.

The study also included data on the vaccine response to Delta in the same period, and shows how different the vaccine’s interaction with Omicron is. Two doses of the vaccine were 85-per-cent effective against symptomatic illness six months after the second dose as long as the patient had Delta instead of Omicron.

“It was not possible for us to study vaccine effectiveness against symptomatic infection before because the data to do so were not available at the time,” Dr. Jeff Kwong, one of the study authors, told CTV News.

But the bottom line, he says, is that “boosters improve protection against symptomatic and severe outcomes.”

Kwong, who is also a scientist with Public Health Ontario and interim director of the Centre for Vaccine Preventable Diseases, pointed out that even a small percentage difference in protection can mean a lot of hospitalizations when you look at how many people are contracting the virus overall.

“Our health system just doesn’t have enough excess capacity to be able to deal with that,” he said. “That’s why our hospitals are now overflowing once again.

“Really, two doses just doesn’t offer a whole lot of protection against Omicron. It’s a different variant.”

Scientists are hoping this Canadian data will convince those sitting on the fence about a booster shot.

“As a pharmacist, I see these conversations a lot and I have them with people,” Tadrous said. “When they talk about, ‘why do I need a booster, I thought you told me two doses and this thing’s over.’

“So this is again, supportive of the need for boosters and the continued action and call for Canadians to get boosters if they’re eligible.”

Tadrous added that studies that track vaccine effectiveness during a rollout are important because they provide real-world data that can reveal things clinical trials may have missed.

“When we roll something out into the real world, it goes to everybody,” Tadrous said. “With vaccines, that may have been limited to some populations, and so what it looks like in the real world is really important.”

Some researchers believe it is data like this that may prompt more regions to require a third dose to be considered fully vaccinated. But so far, the terminology has not shifted.

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Sonja Puzic
sonja.puzic@bellmedia.ca