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People line up outside an immunization clinic to get their Oxford-AstraZeneca COVID-19 vaccine in Edmonton, Tuesday, April 20, 2021.JASON FRANSON/The Canadian Press

Alberta has stopped administering first doses of Oxford-AstraZeneca’s COVID-19 vaccine, except in limited cases, becoming the only government in Canada to make such a move as other provinces weigh their options with remaining doses of the vaccine.

The change is being made both because Canada has the luxury of relying on two other shots for its mass vaccination campaign but also because of the safety concerns of a very rare but serious side effect associated with AstraZeneca. Viral vector vaccines, like those from AstraZeneca and Johnson & Johnson, are linked to a blood-clot condition that mRNA vaccines, from Pfizer-BioNTech and Moderna, are not connected to.

Ontario’s Chief Medical Officer of Health, David Williams, said Monday that the province is reviewing the use of the AstraZeneca vaccine. He and his counterparts in other provinces are still trying to sort out the “right balance” between the risks posed by the vaccine and the risks of COVID-19.

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Canada vaccine tracker: How many COVID-19 doses have been administered so far?

Last week, the National Advisory Committee on Immunization sparked an uproar when it repeated its advice that the mRNA vaccines are preferred to those from AstraZeneca and Johnson & Johnson – where the risk of COVID-19 is lower and the wait for an mRNA shot is short.

Since then there’s been a shift from provinces and some prominent physicians in Canada. However, other than Alberta, no province announced an immediate change to the use of AstraZeneca Monday.

“Our program is transitioned to giving first doses only with mRNA,” said Kristin Klein, an Alberta medical officer of health and a co-lead of the province’s vaccine task force. “Because we have so much mRNA vaccine, those are the vaccines that we are recommending for people to book their first dose with.”

Dr. Klein said people who can’t get an mRNA vaccine for health reasons or simply don’t want one will still be able to get vaccinated with AstraZeneca.

For people who have already had a first shot of AstraZeneca, Dr. Klein said a decision hasn’t yet been made on what their second shot will be. So far, federal health officials say second shots should match first doses. However, Dr. Klein said a decision will be made based on results from pending international studies on mixing doses, and advice from federal officials.

The federal government has said millions more doses of AstraZeneca will arrive by the end of June. To date, it has confirmed shipments of 655,000 doses in the next few weeks and another one million shots in June.

Procurement Minister Anita Anand said last week that the federal government will keep negotiating to get more doses of AstraZeneca sooner. On Monday, however, her office did not provide a statement to The Globe and Mail on whether that will continue. A spokesperson for Health Minister Patty Hajdu, Cole Davidson, said “all vaccines authorized by Health Canada for use in Canada are safe and effective.”

Moderna, Pfizer, AstraZeneca or Johnson & Johnson: Which COVID-19 vaccine will I get in Canada?

Canada pre-purchased millions of doses of seven different vaccine types, and Health Canada has approved four so far for the various provincial and territorial rollouts. All the drugs are fully effective in preventing serious illness and death, though some may do more than others to stop any symptomatic illness at all (which is where the efficacy rates cited below come in).

PFIZER-BIONTECH

  • Also known as: Comirnaty
  • Approved on: Dec. 9, 2020
  • Efficacy rate: 95 per cent with both doses in patients 16 and older, and 100 per cent in 12- to 15-year-olds
  • Traits: Must be stored at -70 C, requiring specialized ultracold freezers. It is a new type of mRNA-based vaccine that gives the body a sample of the virus’s DNA to teach immune systems how to fight it. Health Canada has authorized it for use in people as young as 12.

MODERNA

  • Also known as: SpikeVax
  • Approved on: Dec. 23, 2020
  • Efficacy rate: 94 per cent with both doses in patients 18 and older, and 100 per cent in 12- to 17-year-olds
  • Traits: Like Pfizer’s vaccine, this one is mRNA-based, but it can be stored at -20 C. It’s approved for use in Canada for ages 12 and up.

OXFORD-ASTRAZENECA

  • Also known as: Vaxzevria
  • Approved on: Feb. 26, 2021
  • Efficacy rate: 62 per cent two weeks after the second dose
  • Traits: This comes in two versions approved for Canadian use, the kind made in Europe and the same drug made by a different process in India (where it is called Covishield). The National Advisory Committee on Immunization’s latest guidance is that its okay for people 30 and older to get it if they can’t or don’t want to wait for an mRNA vaccine, but to guard against the risk of a rare blood-clotting disorder, all provinces have stopped giving first doses of AstraZeneca.

JOHNSON & JOHNSON

  • Also known as: Janssen
  • Approved on: March 5, 2021
  • Efficacy rate: 66 per cent two weeks after the single dose
  • Traits: Unlike the other vaccines, this one comes in a single injection. NACI says it should be offered to Canadians 30 and older, but Health Canada paused distribution of the drug for now as it investigates inspection concerns at a Maryland facility where the active ingredient was made.

How many vaccine doses do I get?

All vaccines except Johnson & Johnson’s require two doses, though even for double-dose drugs, research suggests the first shots may give fairly strong protection. This has led health agencies to focus on getting first shots to as many people as possible, then delaying boosters by up to four months. To see how many doses your province or territory has administered so far, check our vaccine tracker for the latest numbers.

The AstraZeneca vaccine makes up just a small part of Canada’s vaccination campaign. Of the 18.1 million doses of COVID-19 vaccines distributed in Canada as of May 6, 2.3 million have been AstraZeneca. As of May 1, two million of those doses have been administered, according to numbers provided by the Public Health Agency of Canada.

The vaccine has been central to Britain’s successful inoculation program. However, its campaign was well under way when public attention turned to reports of the blood-clot condition, which occurs in combination with low platelet levels. In contrast, reports of the blood clots linked to AstraZeneca coincided with the rollout of that vaccine in Canada in early March.

According to Britain’s drug regulator, the incidence of the syndrome, called vaccine-induced immune thrombotic thrombocytopenia (VITT), is about one in 100,000. But other studies in Europe put the incidence at one in 26,000. The Public Health Agency of Canada said the estimated rate is evolving but as of April 28, the rate of VITT in Canada was one case for every 100,000 people vaccinated with AstraZeneca.

So far, 12 cases of VITT have been reported by the provinces, and three people have died as a result, spokesperson Anna Maddison said.

Some countries in Europe are also restricting the use of AstraZeneca. But the changes aren’t unanimous.

Norway and Denmark have both decided to stop using it. Even in Britain, officials now advise against using the vaccine for people younger than 40. With less of the coronavirus circulating and more mRNA shots available, the British advisory panel said the balance had tipped against vaccinating any one younger than 40 with a shot that carries even a small risk of VITT.

Germany, meanwhile, expanded eligibility to all adults who want it, provided they seek guidance from their doctors.

In Canada, a new survey from the COVID-19 Social Impacts Network suggests that public trust has dropped along with the changes in public-health advice. Out of more than 1,500 Canadians who responded to the survey, conducted by the polling company Leger last week, only 44 per cent said they would trust the AstraZeneca vaccine for themselves or for a family member – down from 53 per cent in March. In contrast, trust in the mRNA vaccines is running well above 80 per cent.

As doctors and scientists in Canada have learned more about the frequency of VITT, some are coming out in favour of curtailing or even suspending the use of AstraZeneca for first doses, particularly in light of the millions of doses of mRNA vaccines scheduled to flood into Canada this month and in June.

“At a minimum, nobody should be getting [AstraZeneca] as a first dose,” said Andrew Morris, an infectious-disease doctor at Toronto’s University Health Network and a member of Ontario’s COVID-19 Science Advisory Table.

Dr. Morris added that a case could be made for offering AstraZeneca in places burning with COVID-19, including most of Alberta, Peel Region and parts of Toronto, but not if an adequate supply of mRNA shots can be sent to hot zones instead.

Lynora Saxinger, an infectious-disease physician at the University of Alberta, said she understands why the Alberta government has opted to pause the booking of first-dose appointments of AstraZeneca.

“A pause is not necessarily a bad thing in my books. I just don’t want to consign it to the dustbin permanently until we know a little bit more,” Dr. Saxinger said.

The AstraZeneca vaccine has some important advantages, she added, including the fact that it is easy to ship and store. Dr. Saxinger also said people who have already taken AstraZeneca should be confident they did the right thing, given the situation at the time, including higher case counts and limited vaccine supply.

With reports from Jeff Gray and Ivan Semeniuk

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