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Province to stop administering 1st dose of AstraZeneca vaccine due to risk of blood clots

Last Updated May 11, 2021 at 10:01 pm EDT

Ontario is pausing its province-wide rollout of the AstraZeneca vaccine “out an abundance of caution” citing recent evidence of an increase in VITT blood clotting incidents.

Speaking on Tuesday, Ontario’s chief medical officer of health Dr. David Williams said the decision was made as Ontario receives larger shipments of other vaccines, such as Pfizer and Moderna, adding that those who received the first dose of AstraZeneca could be eligible to get a different shot for their second dose.

The province has seen an increase in VITT in recent days with provincial health officials confirming Tuesday that the risk of a side effect of the blood clotting syndrome has gone from 1 in 100,000 to 1 in 60,000.

The blood clotting syndrome linked to the AstraZeneca vaccine is extremely rare but can be fatal.

“That is a significant safety signal that we do not want to ignore.”

In Canada, at least 12 cases have been confirmed out of more than two million doses given and three women have died.

Ontario says it has 49,280 doses of the shot remaining in the province out of over 707,000 received.

Ontario is preparing guidance for people who already received a first dose of AstraZeneca on what to do next.

Researchers at Oxford University in the United Kingdom launched a study in February designed to investigate the potential benefits of combining different vaccines that require two shots.

The studies are looking into whether taking different types of vaccines generates an immune response similar to, or greater than it would be for someone getting the same shot twice.

Dr. Williams revealed Monday that the province was reviewing the use of the AstraZeneca vaccine as other provinces try to figure out the best method for the remaining doses.

Dr. Theresa Tam, the country’s top doctor, has also said that Canada is closely following the results of the UK study on mixing doses.

As a result, Ontario signalled it would likely mix COVID-19 vaccine brands as the country prepares for a flood of Pfizer and Moderna shots while some doctors question further use of AstraZeneca.

Molecular biologist and science communicator Samantha Yammine said recently some Canadians who have already received the AstraZeneca vaccine may be comforted to know they have the option of a different dose, given recent attention directed at the shot.

“For places in Canada in the midst of a third wave, especially for those who don’t work from home, the up to 94 percent protection against hospitalization from COVID that one dose of AstraZeneca offers was (and is) valuable,” Yammine said on social media.

“#GenXZeneca, and everyone else who took the AstraZeneca/COVISHIELD in Canada as soon as you could: You made the best decision for yourself & your community with all the available evidence. Thank you, and please don’t feel bad about that.”

Alberta became the first Canadian province to cease administering its first doses of Oxford-AstraZeneca’s COVID-19 vaccine as it looked at mixing shots.

The National Advisory Committee on Immunization (NACI) recommended April 23 that people at low risk from COVID-19 wait to get vaccinated until they can access Pfizer or Moderna rather than get AstraZeneca immediately.

NACI said the same thing about Johnson & Johnson on May 3.

A single dose of AstraZeneca has proven to be as good at preventing hospitalizations or deaths from COVID-19 as a single dose of Pfizer or Moderna. That includes both the original SARS-CoV-2 virus that causes COVID-19 and the B.1.1.7 variant of it.

That variant is the dominant one in Canada.

Prime Minister Justin Trudeau emphasized Tuesday that every vaccine shipped to Canada has been found to be safe and effective by Health Canada.

“What we are encouraging Canadians to do is to get vaccinated as quickly as possible, sign up for that first dose and take whatever vaccine is offered to you,” Trudeau said.

Like Trudeau, Dr. Williams stressed that AstraZeneca recipients made the right decision, based on the advice available at the time, to get that vaccine.

Results of a new Leger poll suggest Canadian confidence in COVID-19 vaccines is holding firm despite swirling confusion and concern about the safety of the Oxford-AstraZeneca vaccine.

Among the findings, more than eight in 10 Canadian respondents said they are either vaccinated already or plan to be when it’s their turn.

It’s up from six in 10 people last October, and seven in 10 in January.

Almost all the 2.3 million doses of AstraZeneca already delivered to Canada have been used, and only 655,000 doses are scheduled to arrive this month. Another million doses are expected in June.

Health Minister, Christine Elliott, reiterated the province’s decision Tuesday evening in a tweet.

Elliott added that everyone who did receive the first AstraZeneca, “did the right thing to protect yourselves, your loved ones and communities, and I continue to encourage everyone to sign up for a vaccine as soon as it’s your turn.”

For the residents asking about their second dose, Elliott wrote, “UK data shows a dramatically reduced risk of VITT in second doses of AstraZeneca, and we are also seeing early promising results of administering a second dose of a different vaccine. We look forward to providing more guidance shortly.”

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