‘Very little excuse’ to continue to use AstraZeneca in Canada: infectious diseases specialist

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The peculiar blood clotting disorder linked with Oxford-AstraZeneca’s COVID-19 vaccine, a vaccine now temporarily paused in Ontario and Alberta, doesn’t cause the regular kind of blood clots. These clots require more extensive care, they can’t be predicted and, most importantly, are “really kinda bad,” says a Toronto infectious diseases specialist. The case fatality rate ranges between 20 and 40 per cent.

For those reasons and more, Dr. Andrew Morris believes it’s time to halt AstraZeneca’s shots across the country, except where COVID-19 is burning and people at very high risk of COVID cannot wait for a Pfizer-BioNTech or Moderna shot — mRNA vaccines that haven’t been associated with the same blood clot “safety signal.”

There is “essentially no scenario” outside of the hardest-hit regions where it is beneficial to give AstraZeneca rather than wait for an alternative, Morris, a member of Ontario’s COVID-19 science advisory table, said in an interview. While stressing that he wasn’t speaking on behalf of the table, “there is very little excuse for us to be continuing to give AstraZeneca to Canadians” because the estimated risk of the unusual clotting disorder is higher than earlier, overly optimistic estimates, Morris said.

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At a hastily called news conference Tuesday, Ontario health officials announced the province is pausing first doses of the AstraZeneca vaccine out of an “abundance of caution” because of the risk of thrombosis and an abundance of mRNA vaccine supply. Alberta is also moving to stop using AstraZeneca for first doses.

There is very little excuse for us to be continuing to give AstraZeneca to Canadians

The risk of VITT — vaccine-induced thrombotic thrombocytopenia — now sits at one in 60,000 doses, based on Ontario data. “That’s a significant safety signal that we don’t want to ignore,” said Dr. Jessica Hopkins of Public Health Ontario. The province has about 50,000 remaining doses of AstraZeneca. “Given that we are seeing the overall case numbers of COVID going down and an increase in the safety signal, at a population level, it makes sense to pause AstraZeneca because the risk of severe outcomes with VITT shouldn’t be underestimated.”

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Other provincial medical officers of health across the country are reviewing their use of the controversy-plagued vaccine. The European Union, meanwhile, has opted not to renew its AstraZeneca contracts, which expire in June. In Norway, an expert panel is urging both AstraZeneca and Johnson & Johnson vaccines be ditched over the blood clot scare.

According to Health Canada, the current estimated rate of VITT in Canada is approximately one case per 100,000 persons vaccinated with the AstraZeneca vaccine.

Ontario’s COVID science table, in a brief published Friday, said the risk, based on published estimates, could be as much as one in 26,000.

Morris’ best estimate is that one in 40,000 doses will lead to VITT, a condition that frequently results in complications, with about one in five leading to death and many more cases of severe illness. Given the risk, AstraZeneca only makes sense for those at very high risk of COVID, he said. “But why give them AZ, when we can give them an mRNA vax?”

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Twelve cases of VITT have been reported in Canada, including three deaths. “To me, the most important issue is, we were aware of this a month ago — we probably didn’t appreciate the frequency as much a month ago, although we suspected it,” Morris said.

With two million combined doses of Pfizer and Moderna arriving weekly through May, and 2.4 million combined doses per week scheduled for June, Canada will soon be “swimming in vaccine,” Morris said. “I think that the regulators should say very clearly that, if there are no options for an mRNA vaccine and the incidence of cases is X number, then only in that situation should AstraZeneca be used.”

Some worry this messaging will only make people more confused and concerned. But others agree with Morris. “I’ve done the numbers, too,” University of Toronto epidemiologist David Fisman said on Twitter. “AZ was a useful tool, but our knowledge and understanding, and our supply of other vaccines, has changed. VITT is devastating. We need to move on.”

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Just over two million of the 2.3 million doses of AstraZeneca doses delivered to the provinces had been administered as of Monday. The remaining vials won’t “make or break the pandemic” and the shots are likely going to people who are at relatively low risk of COVID, Morris said, meaning “we’re introducing unnecessary risk into people who have relatively low COVID risk.” The 20 million doses on order from an American plant should be donated to India and other countries, he said.

“If we could get a billion doses of AstraZeneca to India, I would do it in a heartbeat, because so many people are dying. And yes, some of those people will die (from vaccine-induced blood clotting) but you’re going to be saving millions and millions of lives,” said Morris, a professor of medicine at the University of Toronto and infectious diseases doctor at Sinai Health and University Health Network.

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This shouldn’t be construed as buyer’s remorse, he said. People should not feel as if they were somehow “hoodwinked” into getting AstraZeneca. Every authorized COVID vaccine in Canada has been “absolutely life-saving.” A new analysis just out from Public Health England suggests a single dose of either the AstraZeneca or Pfizer-BioNTech vaccine is 80 per cent effective at preventing death from COVID. That rises to 97 per cent after two doses of Pfizer.

If we could get a billion doses of AstraZeneca to India, I would do it in a heartbeat

When COVID is raging, “it’s a total no-brainer (to use AstraZeneca) because, even if you are adding that small risk of harm, it’s outweighed by the benefit,” Morris said.

But outside of hard-hit Calgary, Edmonton, Winnipeg, Peel, Halifax and other pockets, the third wave is cresting or receding in most parts of the country.

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Ontario is offering AstraZeneca to 40 and older. Of the 24,655 COVID-related deaths reported in Canada as of Monday, only 1.6 per cent, or 390, are in people under age 50, and three per cent (749) in people in their 50s.

The blood-clotting syndrome linked to the AstraZeneca vaccine happens four to 28 days after being vaccinated. The mechanism isn’t entirely clear, but it’s thought the body produces antibodies that attack platelets, tiny blood cells that form clots to stop or prevent bleeding. Serious clots have been reported in the brain and other critical organs. The clots can cause strokes, heart attacks and loss of blood supply to a limb.

Canada’s panel of independent vaccination advisors last week reiterated that Pfizer and Moderna remain the “preferred” recommended jabs for all Canadians, and that people at low risk of COVID should consider holding out for an mRNA vaccine, unless they choose to get vaccinated sooner.

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However, the second dose question remains — what happens to those who received a single dose of AstraZeneca? Should they get AZ for dose two? According to U.K. data, the risk of VITT after a second dose of the vaccine is one in a million.

Officials are now awaiting the results of a large study in the U.K. that’s tested alternating doses of AstraZeneca and Pfizer in hundreds of volunteers.

The chances that there will be an issue with mixing vaccines are slim to none

“The chances that there will be an issue with mixing vaccines are slim to none,” said Dr. Allison McGeer, a medical microbiologist and infectious diseases specialist at Toronto’s Sinai Health System. “There are a lot of things keeping me awake at night. This is not one of them.”

“The rules have always been that we don’t ask people to be vaccinated if the vaccine is not a direct benefit to them,” McGeer said. “And the calculus of direct benefit to a person for the AstraZeneca vaccine at the moment is really difficult. It depends on community rates around the person, the individual involved, how well they can protect themselves, how sick they’re going to get if they happen to get COVID, what the probability of VITT is and how long people are going to have to wait for Pfizer or Moderna if they don’t choose to get AstraZeneca.”

With COVID rates dropping in most parts of the country, “that changes the calculations of risk in a non-trivial way,” McGeer said.

“If you got your AstraZeneca vaccine more than a month ago, that’s a good decision with a good outcome,” she said. “I know all sorts of people — my husband, my sister, lots of people — who got the AstraZeneca vaccine and it was a good decision at the time.

“This is the thing about pandemics. New diseases. Things change. The right thing to do changes over time.”

National Post