Dr. David Williams, Ontario's chief medical officer of health, announced Tuesday that the province will stop administering first doses of AstraZeneca COVID-19 vaccine due to increased concerns around vaccine-induced immune thrombotic thrombocytopenia (VITT), which causes blood clots.
"This decision was made out of an abundance of caution due to an observed increase in the observed blood clotting condition...linked to AstraZeneca vaccine," Dr. Williams said.
Ontario's chief medical officer of health confirmed that as of May 8, 651,012 doses of the AstraZeneca vaccine were administered with a rate of VITT of 0.9 per 100,000 dose administered. A total of 202,873 doses of the COVISHIELD vaccine were administered with a rate of VITT of one per 100,000 doses.
"Over the last few days, there has been increase reports of VITT, in particular related to the AstraZeneca vaccine, with a rate of 1.7 per 100,000 doses administered," Dr. Williams said.
Dr. Jessica Hopkins, chief health protection and emergency preparedness officer at Public Health Ontario, confirmed that the province is reporting that the risk of VITT is now one in 60,000 in Ontario. The risk nationally is one in 55,000.
"At a population level, it makes sense to pause AstraZeneca because the risk of severe outcomes with VITT shouldn’t be underestimated," Dr. Hopkins said.
"At the individual level,...there are individual decisions that can be made as well and those are much more nuanced. They depend on your own health, your own risk factors and all of those other things."
Dr. Dirk Huyer, coordinator of the provincial COVID-19 outbreak response, stressed that while this has been considered a rare event, the adverse effect is "severe."
What if you already took the first dose of AstraZeneca?
Despite these concerns, Ontario's chief medical officer of health said Ontarians who received their first dose of the AstraZeneca vaccine made the right decision.
"We maintain that those who received their first dose with the AstraZeneca vaccine did absolutely the right thing to protect illness, and to protect their families, loved one and communities," Dr. Williams said.
"Part of our role with our vaccine safety program,...we're looking for every possibility, every inch of issues that [have] happened, and then we're moving on an abundance of caution to say, let's pause and asses this carefully."
How will people who received their first dose of AstraZeneca COVID-19 vaccine in Ontario get their second dose?
Ontario's chief medical officer of health said he hopes to have answers in the coming weeks around what the options will be for people in the province who are waiting for their second dose, after receiving the first shot of AstraZeneca, stating that the data is being reviewed.
The province has also asked the National Advisory Committee on Immunization (NACI) to provide direction related to the interchangeability of vaccine doses, meaning getting Pfizer or Moderna for their second dose.
Dr. Williams highlight that data from the U.K. is showing there is a reduced risk of VITT when individuals get their second dose, about one in a million, and there are "promising results" of mixing vaccine doses.
Dr. Huyer added that there will also be considerations made around the expiry of currently supply and upcoming shipments, in terms of future administration of AstraZeneca COVID-19 doses.
"This is still a very rare side effect," Dr. Hopkins stressed. "The reason that we're talking about it is because it was one in 100,000 before."
Health experts in Ontario have taken to social media to respond to this latest development in Ontario.
All of this talk of “moving on” from the AstraZeneca #CovidVaccine has done a great disservice to the people who got it. There is still time to fix the message to them.
— Dr. Brian Goldman (@NightShiftMD) May 11, 2021
AZ vaccines will not & should not be wasted. Risk of VITT after dose #2 right now by UK data is ~ 1 in 1 million (4 cases/4.4 Million second doses). But having more vaccine than you know what to do with is the definition of a "good problem" to have.
— Abdu Sharkawy (@SharkawyMD) May 11, 2021
The risk of VITT following a 2nd dose of #AstraZeneca is very likely to be lower than after a 1st dose—the precise risk estimate is still unknown and will likely change with ongoing surveillance.
To quote @ASPphysician we mustn't "say confidently what we don’t know confidently." https://t.co/WUOORbXw4W
— Nathan Stall (@NathanStall) May 11, 2021
Bottom line: Right now, today, in Ontario the risk of WAITING for an mRNA < the risk of taking AZ. That was not true when you (like many other folks I care about) took AZ. Nothing has changed for those who've received 1st shot AZ (though of course this feels bad!)
— Menaka Pai, MSc MD FRCPC (@MPaiMD) May 11, 2021
Finally, those who got AZ - don’t panic/feel remorse. You received a very efficacious vaccine that will protect against severe illness
Remember risk is low, but be familiar w symptoms, seek immediate care. Print & take this, request interpreter at hospital for language barriers. pic.twitter.com/syT8lhypmP
— Sabina Vohra-Miller (@SabiVM) May 11, 2021
Yes this is still true, even though Ontario is pausing further first doses of AstraZeneca 👇🏼 https://t.co/pS6Qdqrctb
— 🔬Samantha Yammine, PhD (aka Science Sam) (@heysciencesam) May 11, 2021
Other individuals also shared reactions on social media in response to the news out of Ontario.
Thinking of everyone in Ontario who took the AstraZeneca vaccine.
Today's announcement to pause first doses was shared in a way that lacked empathy or sensitivity.
Know that everything will be ok and we will get through this.
— Ahmed Ali (@MrAhmednurAli) May 11, 2021
I was literally on my way to get my #AstraZeneca vaccination appointment and was told to turn around because it had been cancelled due to this announcement. Saying I am frustrated is an understatement. https://t.co/VsJQDGyUu5
— Laura Dudas (@Laura_Dudas) May 11, 2021
Serious question: have you ever been clear on anything after listening to Dr. Williams answer a question? Clear really isn't his thing. https://t.co/6i2khPOQk4
— Mike Belmore (@Happy_Belmore) May 11, 2021