Alberta was the first province to confirm that it stop giving the first doses of AstraZeneca vaccine, citing a scarcity of supply. The province will instead prioritize mRNA vaccines like Pfizer-BioNTech and Moderna while reserving the existing AstraZeneca for second doses. Ontario Chief Medical Officer Dr. David Williams announced in an impromptu press conference Tuesday afternoon that the vaccine would no longer be offered to Ontarians as a first dose and that future supply would instead be reserved for optional second injections.
But unlike Alberta, Ontario’s decision was made largely due to the increased rate of the rare but serious vaccine-related blood clotting disease known as immune-induced thrombotic thrombocytopenia. vaccine (VITT).
Those of you who received your first dose of AstraZeneca have done what it takes to protect yourself, your loved ones and your communities, and I continue to encourage everyone to sign up for a vaccine as soon as possible. it’s your turn.
Williams said that over the past few days there have been an increasing number of reports of VITT in Ontario. Of the more than 850,000 doses of AstraZeneca administered, there were now eight cases in the province on Saturday at a rate of about one in 60,000 injections administered.
Other provinces have yet to follow suit, but there are growing signs that the vaccine will not be prioritized in provincial and territorial deployments across the country.
WATCH | Ontario will no longer give AstraZeneca COVID-19 vaccine as the first dose due to the risk of a blood clot:
The Quebec Department of Health and Social Services said in a statement to CBC News that although the AstraZeneca vaccine is still technically available for people over 45, the remaining doses have almost all expired and mRNA vaccines. will be offered if a second dose is not available.
Dr Brent Roussin, Manitoba’s chief provincial public health officer, said on Sunday the possibility of stopping the use of the AstraZeneca vaccine was being discussed “on several levels.”
British Columbia provincial health worker Dr Bonnie Henry said on Tuesday that while second doses of the AstraZeneca vaccine will be available to those who have already received a vaccine in the province, mRNA vaccines will also be an option. .
Further international research is expected in the coming days and weeks on the safety and effectiveness of mixing and pairing COVID-19 vaccines, and Canadians who have received an initial dose of AstraZeneca will likely have the opportunity to combine it with an mRNA injection.
“I can’t stress enough how important AstraZeneca is, especially in March and April when we had limited amounts of mRNA vaccine and we had high case rates and it’s a very good vaccine and very protective, ”she said. CBC’s The Early Edition.
“But since we have case rates that are fortunately declining and hopefully staying low, and we have a lot more other vaccines available, we’re going to consider using the Pfizer and Moderna that are coming in. ”
VITT data “evolves” in real time
The abrupt shift in vaccine deployment strategy follows growing concerns from health experts about the risk of VITT, which they say calls into question its continued use in Canada.
Dr. Andrew Morris, an infectious disease specialist at the University of Toronto, says the use of the AstraZeneca vaccine in Canada is no longer justifiable, especially among young people.
“For people who are between 30 and 40, it just doesn’t make sense,” he said. “They are at very low risk of dying from COVID and they take the risk of dying from it.”
Health Canada approved the AstraZeneca vaccine for all Canadians over 18 in February, but provinces and territories have largely restricted its use in people over 40 due to the increased risk of VITT in groups of younger age compared to the risk of death from COVID-19.
Although extremely rare, VITT is much more serious than a typical blood clot because it can cause cerebral venous sinus thrombosis (CVST), where the veins that drain blood from the brain are blocked and can potentially cause fatal bleeding. .
Dr. Menaka Pai, clinical hematologist at McMaster University and member of the Ontario COVID-19 Scientific Advisory Table, says the risk of VITT changes almost daily and guidelines are to be expected different.
“The reality is, this is what evolving science looks like,” she said. “We ask people to make real-time decisions with the information we have, then the information changes a week later and we can regret the decision of a week ago, but the hindsight is 20/20. ”
Pai says each region of the country needs to examine its specific epidemiological situation in the pandemic and determine whether the risk of VITT outweighs the risk of serious consequences from COVID-19.
“What works in a hotspot where you don’t have enough mRNA vaccines to quickly cover everyone [may not work] in some parts of the Maritimes where you actually have a lot of low prevalence places, ”she said.
“If you don’t have the privilege of choosing because your pandemic is out of control, I think it changes the math a lot and it changes the decision making. ”
Risk of VITT “increasing” as cases identified
Canada reported 12 confirmed cases of VITT on Monday out of more than 2.3 million doses of AstraZeneca administered, according to the Public Health Agency of Canada. Quebec, Alberta and New Brunswick have each reported one death; New Brunswick has only 40 deaths from COVID-19 overall.
“In a low risk province of COVID-19 like New Brunswick, the risk of death from VITT outweighs the risk of death from COVID-19 at any age,” said Dr. David Fisman, epidemiologist at the University of Toronto Dalla Lana School. of public health.
Ontario Science Table Now estimates the frequency of VITT among Canadians who have received the AstraZeneca vaccine at 1 in 55,000, but that number is a moving target with new data released daily from countries around the world.
“Risk estimates increased as people started looking for the complication,” Fisman said. “It doesn’t make sense to use a vaccine where the short-term damage outweighs the short-term benefits, when people can stay safe until they get the mRNA vaccine. ”
The National Advisory Committee on Immunization (NACI) was criticized last week for its post regarding its recommendations to provinces and territories that mRNA vaccines such as Pfizer-BioNTech and Moderna, which do not pose a risk of VITT, were ” prefer. »
PHAC said in a statement to CBC News that as the supply of mRNA vaccines like Pfizer and Moderna increases this month, it is “expected” that provinces and territories “will continue to review and adjust their vaccination programs ”.
WATCH | Tam talks about second doses of AstraZeneca and vaccine mix
Morris says he believes more cases and deaths from VITT will occur in Canada in the future if we continue to use the AstraZeneca vaccine as part of our vaccine deployment.
“You have to be pretty sure that the people you give it to are at a really, really, really high risk of death from COVID,” he said. “So that the risk of death to which you expose them is exceeded by the risk of death that you avoid.”
Use of AstraZeneca in other countries
Denmark has completely discontinued the use of the AstraZeneca vaccine due to the risk of VITT, in addition to the Johnson & Johnson vaccine, which uses a similar adenoviral vector method. This decision should set the country back several weeks in the deployment of its vaccines.
The UK has used the AstraZeneca vaccine as part of its vaccination campaign to successfully control its pandemic and is now able to relax public health restrictions largely due to the use of shot.
But VITT was not yet identified when this deployment was in full swing earlier this year and in the UK restrict the vaccine to over 40s last week and retroactively reported 242 cases of VITT and 49 deaths out of 28.5 million doses administered through April 28.
According to the Ontario Science Table, VITT can present from four to 28 days after vaccination and Canadians should see a doctor if they experience any of the symptoms listed. on his website.
Pai says that Canadians who fear taking an initial dose of the AstraZeneca vaccine when they are not showing symptoms of VITT should rest assured that they have made a wise choice at a critical time in the pandemic.
“You made an incredible, incredible decision based on the information you had,” she said. “And now doctors, like me, are trying to let you know if there is a very rare risk. “