Why restricting AstraZeneca vaccines in Canada means balancing ‘vaccine risk vs. disease risk’

3rd wave hitting younger Canadians harder, but AstraZeneca vaccine only for 55+ due to rare blood clot risk

The decision to restrict the use of one of four approved vaccines at a time when COVID-19 levels are rising again in Canada’s hardest hit provinces is a tough pill to swallow, but makes sense given the lack of data on a rare blood clot risk, experts say. (John Woods/The Canadian Press)

Adam Miller · CBC News · Posted: Apr 03, 2021

This is an excerpt from Second Opinion, a weekly roundup of health and medical science news emailed to subscribers every Saturday morning. If you haven’t subscribed yet, you can do that by clicking here.

[Excerpt] Canada’s decision to suspend the use of the AstraZeneca-Oxford vaccine in Canadians under 55 during a surging third wave and a slow vaccination rollout is a calculated risk.

The National Advisory Committee on Immunization (NACI) updated its guidance to provinces and territories against the use of the vaccine for younger Canadians on Monday, following reports of rare but potentially fatal blood clots in Europeconnected to the shot.

Health Canada says the benefits of the vaccine to protect against COVID-19 still outweigh the potential risks, with more than 300,000 doses of the shot administered and no cases of the serious clotting condition, known as vaccine-induced prothrombotic immune thrombocytopenia (VIPIT), in Canada. 

But the decision to restrict the use of one of four approved vaccines at a time when COVID-19 levels are rising again in Canada’s hardest hit provinces is a tough pill to swallow for some.

“It can be a very powerful tool when we’re at this stage of the pandemic where we’re talking about, in hotspots at least, the system getting to a point of potential collapse,” said Dr. Susy Hota, an infectious disease specialist at the University Health Network and an associate professor of medicine at the University of Toronto. 

“There are humans behind that story, and when you’re in a hospital where you’re seeing an exponential rise in the number of COVID-positive patients coming in, and your staff to help manage these patients is the same pool of staff — then those numbers aren’t adding up.”

But on an individual level, experts say the lack of data on the risk of VIPIT to Canadians from the AstraZeneca vaccine is concerning and NACI was right to err on the side of caution in order to avoid putting lives unnecessarily at risk. 

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