Canada confirms case of rare blood clot after AstraZeneca COVID-19 vaccine


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The first confirmed case of a rare but potentially fatal blood clot has been recorded in Canada in connection with the AstraZeneca-Oxford COVID-19 vaccine.

Quebec’s Ministry of Health and Social Services confirmed a person in the province experienced an adverse event known as vaccine-induced prothrombotic immune thrombocytopenia (VIPIT).

The ministry didn’t confirm the age or gender of the person, but Quebec Health Minister Christian Dube later identified the individual as a woman.

“The good news is, the woman in question was taken care of and she’s doing well,” he said during a news conference Tuesday.

The National Advisory Committee on Immunization (NACI) said last month VIPIT occurs at a rate of about one in 100,000 people vaccinated, with a mortality rate of about 40 per cent, although more research is needed and that risk is reduced if treated early enough.

Dube said the province is taking a “hypervigilant” approach and keeping a close eye on any adverse reactions related to the vaccine. He said this was a possibility that health officials “expected” and prepared for.

“We have been very transparent that there could be one case per 100,000,” he said. “We knew this could happen.”

The Public Health Agency of Canada said in a statement Tuesday that an individual living in Quebec had been identified as the country’s first case after receiving the AstraZeneca-Oxford Covishield vaccine produced at the Serum Institute of India and that the woman is now at home recovering.

PHAC declined to provide further details on her age, the time frame in which she got the shot or whether it involved a first or second dose of the vaccine.

“It’s clear that VIPIT is associated with this vaccine. It just appears to be a very, very rare event,” said Dr. Isaac Bogoch, an infectious diseases physician at Toronto General Hospital and member of Ontario’s COVID-19 vaccine task force.

“We’ve given out hundreds and hundreds of thousands of doses, there has been one confirmed case to date and it would come to no one’s surprise if there were additional cases.”

Dr. Menaka Pai, a clinical hematologist at McMaster University in Hamilton and a member of Ontario’s COVID-19 Science Advisory Table who works closely with PHAC officials on VIPIT, said Quebec physicians did a “fantastic job” acting quickly to identify and treat the patient.

“She developed classic symptoms of a blood clot and they occurred in what we believe is the time period for VIPIT to occur, which is between four and 20 days post-vaccination,” she said.

“They were able to use the guidance that we’ve pulled together, they were able to arrange testing in a timely manner, and this is just an example of them really stepping up to diagnose and treat a very rare and serious type of event.”

Canada’s chief public health officer spoke with reporters during the regular Tuesday pandemic briefing in Ottawa. 1:54

NACI Chair Dr. Caroline Quach said last month the risk of rare blood clots appears to only occur in younger populations, which is why the committee recommended suspending the AstraZeneca-Oxford vaccine in those under 55.

Every province and territory in Canada then moved to suspend the use of the vaccine in Canadians under 55 until more information was known about the condition and its connection to the vaccine.

Quach also said the vaccine works well in preventing severe outcomes and death in people over 55, particularly in those over 70, and the risk of blood clots does not appear to be present in those age groups.

“It was only a matter of time before we were going to see a case of this when we give out enough of this vaccine,” said Bogoch.

“We have to be transparent about what the risk is and it’s important to frame that risk in the appropriate context.”

The total number of people in Europe who got the rare blood clots after vaccination is small — as of this month, dozens of cases have been reported compared to millions who received the shot.

But the people who appear to have an elevated risk of the rare blood clots are not the same age group most at risk from COVID-19.

“This is a very effective vaccine for preventing COVID-19 and we’re in the middle of a third wave in much of the country and the risk of getting COVID-19 is high,” said Bogoch.

“Based on what we know today, the benefits outweigh the risks — especially when we’re dealing with the 55 year old and older crowd.”

Canada has had more than 23,000 COVID-19 deaths in the year since the pandemic began, but fewer than a thousand of those have been people under 60. Just over 300 deaths have been Canadians under 50.

The Public Health Agency of Canada released a statement on March 29 saying that “there is no cause for concern” for Canadians who have already been vaccinated with AstraZeneca for more than 20 days but that you should seek immediate medical attention in the rare event you develop the following symptoms four or more days after vaccination:

  • Shortness of breath.
  • Chest pain.
  • Leg swelling.
  • Persistent abdominal pain.
  • Sudden onset of severe or persistent worsening headaches or blurred vision.
  • Skin bruising (other than at the site of vaccination).

PHAC said decisions on the type of second dose that will be offered to those who have been vaccinated with AstraZeneca will be determined based on the “latest evidence and research.”

Most of the complications in Europe occurred within 14 days of receiving the AstraZeneca shot, and the majority were in women under the age of 55.

Pai, the clinical hematologist at McMaster University, said the adverse blood clotting event is still “extremely rare” and officials need to balance the risk of administering the vaccine with the risk of COVID-19.

“We have to consider what the risk is of not taking the vaccine,” she said.

“I know people are really worried, but as a front-line physician myself who’s watching this virus rip through the province of Ontario, I think that people still should take the first vaccine that’s offered to them.”

Pharmacist Abraam Rafael administers a COVID-19 vaccine to Maureen Doyle at his pharmacy in Toronto. (Cole Burston/The Canadian Press)

British regulators said on April 1 they had identified 30 cases of the rare blood clot events after the use of the AstraZeneca-Oxford vaccine, 25 more than the agency reported in mid-March.

Pai said the risk of VIPIT from the vaccine was between one in 100,000 and one in 250,000 based on the updated British numbers, but that number is subject to change as more information comes in.

“What Canadians really want to know is, what is my individual risk of this is?” she said, explaining that it is difficult to give accurate personalized risk assessments in Canada with just one case identified in isolation.

“This is one case and we have to be really careful not to extrapolate and make our decisions based on the one case.”

Bogoch says he hopes the VIPIT case doesn’t significantly change the current vaccine rollout in Canada, but that provinces need to be able to pivot to other vaccines if necessary.

“We have enough Pfizer and Moderna to vaccinate everyone in the country,” he said. “It just means the rate of vaccination would slow down.”

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