The province has temporarily halted administering first doses of the AstraZeneca vaccine amid increased reports of blood clotting health officials said on Tuesday.
Ontario’s Chief Medical Officer of Health Dr. David Williams who announced the pause said the decision was in response to new data suggesting an increased risk of vaccine-induced thrombotic thrombocytopenia (VITT), now one in 60,000 people rather than one in 125,000.
“It is not that the risk for individuals has gone up extensively at this time but because it is sometimes severe we want to be cautious,” he said.
He said the data and information is being further reviewed by Health Canada and NACI while reassuring Ontarians who have already received their first doses that they did the right thing.
“We maintain that those who received their first dose with the AstraZeneca vaccine did absolutely the right thing to prevent illness, and to protect their families, loved ones, and communities,” Dr. Williams said.
There have been eight cases of vaccine-induced blood clotting reported in Ontario so far and while the condition remains extremely rare, it can be fatal.
The province’s top doctor said that with supply of other vaccines, specifically Pfizer, ramping up considerably the province found itself in a position in which it could suspend the use of AstraZeneca for now “out of an abundance of caution”.
Dr. Williams also said that the declining case numbers in Ontario were a factor in the decision as it could mean that the risk of ending up in hospital from a vaccine-induced blood clot will eventually exceed the risk of being hospitalized due to COVID-19.
Chief Health Protection and Emergency Preparedness Officer Dr. Jessica Hopkins explained further.
“When you look at risk on a population level what we’re really looking at is you know overall does this safety signal give us enough concern that we preferentially choose other products,” Dr. Hopkins said. “At this point in time, and given that we’re 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.”
The province still has about 50,000 doses of AstraZeneca with 25,000 more expected. Officials say they don’t know what to do with them yet while adding that research out of the United Kingdom suggests the risk of blood clotting goes down to one in a million after the first dose.
Meanwhile Prime Minister Trudeau has said he will be getting his second dose of the AstraZeneca vaccine.