'Preferred vaccines' messaging from federal panel sparks concern, criticism from health experts

Canadians should take the first vaccine that becomes available to them even though the federal government's advisory committee on vaccines may have sown confusion with conflicting messaging about preferred doses, some health experts say.

mRNA vaccines such as Pfizer and Moderna are the preferred vaccines, according to NACI

Canadians should take the first vaccine that becomes available to them even though the federal government's advisory committee on vaccines has sown confusion with conflicting messaging about preferred doses, some health experts say. (Chris Young/The Canadian Press)

Canadians should take the first vaccine that becomes available to them even though the federal government's advisory committee on vaccines may have sown confusion with conflicting messaging about preferred doses, some health experts say.

"I really worry about a situation where Canada will be the only country in the world where we've managed to create buyer's remorse about a vaccine we've provided free of charge to Canadians to protect them," Dr. David Naylor,  co-chair of the national COVID-19 Immunity Task Force, told CBC's Heather Hiscox.

On Monday, the National Advisory Committee on Immunization, an independent body of experts that makes recommendations on the use of newly approved vaccines, said Canadians who are less likely to contract COVID-19 may want to wait until an mRNA shot from Pfizer-BioNTech or Moderna is available because those products don't carry the same risk of very rare, but serious, blood clots.

NACI's modified recommendations appeared to contradict what health experts have said for months, that Canadians should take the first vaccine that becomes available and not shop around.

"What we're saying, and what we've been saying all along, is that the mRNA vaccines are the preferred vaccines," said Dr. Shelley Deeks, the vice-chair of NACI.  "Yet given the epidemiology, the viral vector vaccines are very effective vaccines, but there is a safety signal, a safety risk."

NACI says vaccine-induced immune thrombotic thrombocytopenia (VITT) occurs at a rate of about one in 100,000 people vaccinated with the AstraZeneca vaccine and has a mortality rate of about 40 per cent, although more research is needed — and that number is subject to change.

WATCH | Dr. David Naylor talks about NACI's conflicting vaccine messages:

Conflicting vaccine messages could cause 'buyer's remorse': Expert

3 years ago
Duration 10:19
Featured VideoChanging guidance on COVID-19 vaccines in Canada could lead some people to regret getting the shot that was available to them at the time, says Dr. David Naylor, co-chair of the national COVID-19 Immunity Task Force. He says all of the vaccines available in Canada are very effective.

Based on current data, NACI estimates VITT occurs at a rate of one in 100,000 shots rather than the one in 250,000 previously projected.

'We modified the recommendations'

"When we first provided recommendations for COVID vaccines in Canada, we did not know about the vaccine safety signal. Now there's been a vaccine safety signal and we modified the recommendations," Deeks said.

Dr. Peter Juni, scientific director of the Ontario COVID-19 Science Advisory Table, said he agreed with NACI's modified recommendations.

"I have big respect for NACI that they did that. And it's absolutely the right thing to do," he said.

Prime Minister Justin Trudeau looks on as pharmacist Zaineb Hassan administers the COVID-19 AstraZeneca vaccine to Sophie Grégoire Trudeau in Ottawa on April 23. (Adrian Wyld/The Canadian Press)

Juni said while such incidents of VITT are indeed rare, they are now five or 10 times more likely to occur than originally thought. 

"Does this change the picture? Yes it does," he said. 

Still, other experts such as Naylor expressed concerns that NACI's new messaging suggests that the mRNA vaccines are superior in efficacy and that Canadians may regret getting an AstraZeneca vaccine.

"That's a very problematic position to take," he said.

Naylor stressed that all the vaccines do extremely well at protecting people from serious complications, hospitalizations and death.

And for those who already received a shot of AstraZeneca, "it is an unsettling message [from NACI] because it suggests you got the second-best vaccine," he said.

Dr. Susy Hota, medical director for infection prevention and control at University Health Network in Toronto, reaffirmed that Canadians should not vaccine shop and that the bottom line of trying to protect people from the hazards of getting COVID-19 has not changed.

WATCH | NACI says Pfizer and Moderna COVID vaccines are the preferred type:

Vaccine advisory group says Pfizer and Moderna COVID vaccines are the preferred type

3 years ago
Duration 2:33
Featured VideoDr. Shelley Deeks of NACI discussed with reporters the merits of receiving one type of COVID-19 vaccine over another.

She said she still believes in most parts of Canada where there's enough transmission of COVID-19, the risks of acquiring the virus and the associated complications outweighs any of the risks from the vaccines.

'Worries me a lot'

Hota also said she's concerned how NACI's recommendations may fuel vaccine hesitancy.

"That worries me a lot," she said. "I worry about people who've been sitting on the fence, just kind of biding their time or waiting for [a vaccine] to become available to them in their category of age or whatever, now feeling like even though they were confident in their decision before, they're not so confident anymore."

Timothy Caulfield, Canada Research Chair in health law and policy at the University of Alberta, said the risks need to be put into context. That includes 17 events of severe blood clotting in the U.S. from the Johnson & Johnson vaccine out of eight million doses. And with the odds of getting VITT around one in 100,000 with AstraZenenca, the risks overall are "incredibly rare," he said.

He said NACI is creating a hierarchy with respect to vaccines and not focusing enough on the profound benefit that the vaccines have for the general public, for hitting herd immunity and for decreasing community spread.

"I am frustrated by the messaging that has emanated from the committee, especially right now when there's jurisdictions like Alberta and Ontario that are really struggling," he said.

"It matters a huge amount, especially now, when we're going to start to bump up against hesitancy. So if poor messaging results in one or two or three per cent of people not getting the vaccine or even waiting to get the vaccine, that matters."

Poor messaging

Dr. Zain Chagla, an infectious diseases physician at St. Joseph's Healthcare Hamilton and an associate professor at McMaster University, said he is receiving a lot of questions from people second guessing their decision to get the AstraZeneca vaccine. 

"It's like no, no, no, you did the right thing. You got it. You're reducing your risk of hospitalization or reducing your risk of death," he said.

Chagla said NACI appears to be giving advice for a situation in which, there's a bubble, where there's no COVID-19 or very little circulation around. 

"I don't disagree with the medical sentiment that there is a risk of this clotting issue," he said. "That's advice given in a vacuum of not really looking at the world that it is today."

Still, Juni said he believes some of his colleagues have not understood the seriousness of the type of thrombosis associated with the non-mRNA vaccines. 

With a new understanding that these events are more frequent, much more serious and potentially fatal, combined with more mRNA vaccines available, "the risk benefit balance starts to change." he said.

"Even if it's a rare event, it's now just something which needs to be openly discussed so that people can make an informed decision."


Mark Gollom

Senior Reporter

Mark Gollom is a Toronto-based reporter with CBC News. He covers Canadian and U.S. politics and current affairs.

With files from John Paul Tasker, Adam Miller

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