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Pharmacist Mario Linaksita administers the Oxford-AstraZeneca COVID-19 vaccine to Sharon Berringer, 56, at University Pharmacy in Vancouver on April 1, 2021.DARRYL DYCK/The Canadian Press

Health Canada is standing by the approval of the Oxford-AstraZeneca and Johnson & Johnson vaccines for all adult ages despite some international hesitancy to use the shots because of rare but severe blood clots.

The Canadian regulator updated guidance to citizens and the medical community Wednesday saying AstraZeneca vaccine recipients should be warned about the 1-in-250,000 risk of blood clots but immunization should continue as most of Canada struggles to control a rapid rise in COVID-19 cases.

“Where the risk of COVID is moderate or high, as it is in many parts of the country, the benefits of the AstraZeneca vaccine far outweigh the risks, in all age groups,” said Supriya Sharma, Health Canada’s chief medical adviser.

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The United States paused the use of the Johnson & Johnson vaccine this week. Health Canada officials said Wednesday they are also following those developments but blood clot issues with that vaccine also appear to be “very rare,” with six cases reported following 6.8 million doses administered. Canada has yet to receive any shipments of that vaccine.

Health Canada made its AstraZeneca decision on the same day Denmark decided to suspend its use. While Denmark endorsed the European Medicines Authority’s approval of the vaccine, authorities in the country said its current low prevalence of COVID-19 and the availability of other vaccines allowed it to set aside AstraZeneca.

“We have other vaccines at our disposal, and the epidemic is currently under control,” said Soren Brostrom, director-general of the Danish Health Authority, in a statement. He said Denmark “would not hesitate to use the vaccine” if it was experiencing a massive third wave, if the health system was under pressure, or if it was short vaccines.

In Canada, the National Advisory Committee on Immunization recommended AstraZeneca use for those 55 and older because most blood clot issues appeared among younger women.

Health Canada sent the latest guidance to NACI and the provinces. Committee chair Caroline Quach-Thanh said she and her colleagues were “reviewing if we maintain our position or modify age following Health Canada’s report.” The committee is also finalizing recommendations on the Johnson & Johnson vaccine while keeping an eye on information emerging from U.S. regulators, she said.

Health Canada officials reviewed international evidence, particularly from Britain, which used 20 million doses of AstraZeneca by the end of March. The country had 79 cases of blood clots likely linked to vaccination. Seven people died.

Canada’s lone blood clot case linked to COVID-19 vaccination happened to a Quebec woman who was above 55 years old and had received the Covishield version of the AstraZeneca vaccine. She was treated and is recovering at home. Canadians have received at least 600,000 AstraZeneca vaccines, including those under the Covishield name.

The Health Canada advisory warns the medical community and vaccine recipients to look out for persistent and severe headaches, abdominal or limb pain, or unusual bruising for four to 20 days after the shot.

Dr. Sharma pointed out other medications and simply being a woman present far greater blood clot risk than the AstraZeneca vaccine risk of 1 in 250,000. Women 15 to 45 have a 1-in-3,300 risk of having a blood clot, 1-in-1,600 if they are on birth control pills, 1-in-300 while pregnant, and 1-in-100 after pregnancy. Among COVID-19 patients, 1 in 5 develop blood clots.

While other clots are different and often less severe, Dr. Sharma emphasized the statistics illustrate the rarity of the vaccine clots.

Provincial premiers who rely on NACI for guidance urged it to expand eligibility for AstraZeneca to lower age groups in line with the Health Canada advice. The latest shipment of AstraZeneca started being administered to 55-and-older people one week ago.

Alberta’s Jason Kenney said he’s heard some confusion and concern about the vaccine. The province set up high-volume clinics in several cities and walk-in pharmacy clinics for AstraZeneca. “A lot of those doses are just sitting there,” Mr. Kenney said.

Ontario Premier Doug Ford added he hopes NACI lowers the recommended age to 50. “We need an answer ASAP. It’s absolutely critical. And if they lower the age, then we’ll be able to get more uptake on it,” he said.

In Quebec, where television personalities and public officials have flooded newscasts and social media with selfies getting AstraZeneca shots, the vaccine is being snapped up in some centres but passed over in others. Provincial Health Minister Christian Dubé, who got the vaccine himself, said the campaign is a success, so far.

The province administered 120,000 of 330,000 available AstraZeneca doses in five days, hitting a record 23,600 on Tuesday. More than 40,000 people are booked for AstraZeneca appointments in coming days, on top of drop-ins. “It’s not running out of steam,” Mr. Dubé said.

The irregular national uptake of the vaccine is reflected in opinion polling. A poll published this week by the Angus Reid Institute found 69 per cent of Canadians intend to get a vaccine – a high since the pandemic began – but just 41 per cent would be comfortable getting the AstraZeneca shot.

Angus Reid Institute president Shachi Kurl said the results are a warning to officials they have work to do to convince Canadians to sign up for AstraZeneca. “AstraZeneca troubles are deeply saturated in the Canadian psyche,” she said. But all is not lost for the vaccine, she added.

“Public opinion is malleable. It changes, it’s organic,” she said. “We see that in politics, we see it in other areas where circumstances change. Canadians have massive levels of trust in public-health officials. They now have to use that influence to address it.”

With reports from Ivan Semeniuk in Toronto and James Keller in Calgary.

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