Why I Got the AstraZeneca COVID-19

How the risks of the AstraZeneca COVID-19 vaccine stack up against the waiting game.

Chana Davis, PhD
11 min readApr 28, 2021


If you were offered a shot of the AstraZeneca COVID-19 vaccine, would you take it? If you’d hesitate, you’re not alone. Many Canadians would rather hold out for Pfizer or Moderna mRNA vaccines, than take AstraZeneca.

The Great COVID-19 Vaccine Dilemma is a problem we’re lucky to have, but is weighty nonetheless. To resolve my own dilemma, I dug into the latest science to estimate my risk of blood clots from the AstraZeneca vaccine, my risk of serious COVID-19 outcomes while playing the waiting game, and the real-world performance of COVID-19 vaccines.

For me, the answer was clear — get the shot, ASAP. My risk of a vaccine-related blood clot is lower than the risks I face from being exposed to COVID-19 over two months. Furthermore, it turns out that we can’t assume that Pfizer is a better bet than AstraZeneca. Science communicators have been warning us to avoid making “apples to oranges” comparisons between vaccine trials, and it’s time to start listening (see Vox and Dear Pandemic).

My risk calculus applies to my context — a healthy woman in her forties, in a region with moderate COVID-19 levels, with low to moderate exposure to COVID-19 through my three young children who are attending school. The information below can and should be adapted to your situation, so that you can make an informed choice.

So many names! The AstraZeneca vaccine is also known as the COVISHIELD vaccine (made in India), Vaxzevria, and Oxford-AstraZeneca.

Is the AstraZeneca vaccine safe? What are the risks?

Photo by camilo jimenez on Unsplash

The AstraZeneca COVID-19 vaccine has been linked to rare but serious adverse events — potentially fatal blood clots. They are thought to occur through a different pathway than most common blood clots, one that mimics autoimmune heparin-induced thrombocytopenia (HIT). This phenomenon is called Vaccine-Induced Prothrombotic Immune Thrombocytopenia (VIPIT) or Vaccine-induced Immune Thrombotic…



Chana Davis, PhD

Scientist (PhD Genetics @Stanford) * Mother * Passionate about science-based healthy choices * Lifelong learner * Founder: Fueled by Science