While provinces across Canada are lowering the age of eligibility for AstraZeneca from 55-plus to 40-plus, the vaccine’s link to extremely rare blood clots may still be a source of hesitancy for many women.
Reports of the vaccine-related clots emerged in early March, with most of the cases in Europe involving women under the age of 55. Canada’s first four cases—out of more than 1.1 million doses of vaccines administered—popped up in April: a Quebec woman over the age of 55; a man from Alberta and a man from Ontario, both in their 60s; and an individual in New Brunswick in their 30s. All of them received the AstraZeneca vaccine.
After completing an independent assessment, Health Canada concluded that these very, very rare events may be linked to the vaccine—but that the benefits still outweigh the risks, and the agency announced last Wednesday that it is not restricting the use of AstraZeneca.
We spoke with medical experts about these risks and why it’s still very much worth taking the AstraZeneca vaccine if you’re eligible.
What kind of blood clot is linked to AstraZeneca?
The rare condition is called vaccine-induced immune thrombotic thrombocytopenia, a.k.a. VITT. It’s associated with low levels of platelets, which are the blood cells that produce clots to prevent us from bleeding. The body’s immune system attacks these blood platelets, which leads to clotting.
Many of the early reported cases of VITT involved extremely rare clotting at the base of the brain called cerebral venous sinus thrombosis (CVST), while other cases occurred in veins elsewhere in the body.
“This is a very different process for forming blood clots than we see after surgery or in somebody who has a family clotting disorder, [those have] very little to do with the immune system,” explains Dr. Lori-Ann Linkins, a thrombosis consultant and an associate professor at McMaster University in Hamilton, Ont.
There is very little data on how age, gender or pre-existing medical conditions might contribute to the development of VITT (also referred to as VIPIT), but research is being done in Canada to identify and treat the rare blood clots.
What’s the risk of getting this blood clot?
“It’s a very low risk,” says Dr. Michael Gardam, the Medical Director of Infection Prevention and Control at Women’s College Hospital in Toronto. “You have to balance that with the risk of potentially catching COVID-19 and getting really sick, being hospitalized and developing those long COVID symptoms.”
To date, Canada has administered over 1.1 million AstraZeneca vaccines and so far only four people have developed VITT from taking the shot. All of them have been treated and are recovering. The European Medicines Agency (EMA) says the risk of developing a blood clot from the AstraZeneca vaccine is one in 100,000, compared to the up to 20 percent chance of developing a blood clot from being infected by COVID-19.
Does taking hormonal birth control pills affect the risk?
Dr. Andreas Greinacher, a German clotting specialist from the University of Greifswald, led the research team that discovered the link between AstraZeneca and blood clots. He noted that not all of the women who developed VITT were taking contraceptives, which means hormonal birth control is an unlikely factor.
By itself, birth control comes with its own risk of blood clots. In fact, Linkins says the risk of developing a blood clot just from taking hormonal birth control is much higher than from the AstraZeneca vaccine.
“Why do millions of women accept this risk? Well, it’s because it actually is a very, very small risk and the benefits of preventing pregnancy for people who don’t want to become pregnant greatly outweighs the tiny risk,” she says. “I would argue the same is also true for taking the vaccine.”
What about people who have had previous blood clots or have a family history of blood clots?
According to Thrombosis Canada, these factors could put you at a higher risk for future clots in general, but the COVID-19 vaccines do not increase this risk.
So, how do AstraZeneca’s benefits greatly outweigh the risks?
“Don’t make decisions based on fear, make decisions based on information,” Linkins emphasizes.
The fact is, AstraZeneca’s benefits do greatly outweigh the risks. The vaccine is 76 percent effective in preventing symptomatic COVID-19 cases and is 100 percent effective in preventing hospitalization and death.
Gardam adds that AstraZeneca is key in helping the entire world get vaccinated, since it’s inexpensive and can be stored in regular fridge temperatures. “That should matter to Canadians, not just for humanitarian reasons, but also because if the pandemic isn’t controlled elsewhere, it won’t be controlled at all.”
When it comes to assessing the risks, it’s important to ask questions. Linkins says to consider whether what you do for a living exposes you to a lot of people. Are you a teacher, grocery store worker or healthcare provider? If so, your risk of getting COVID-19 is astronomically higher than the risk of developing VITT.
Are you staying away from your family, neighbours, friends? If not, every time you interact with people, you’re potentially exposing yourself to people they’ve come in contact with.
“You have to put the risks of you contracting COVID-19 and potentially dying from it against the risk of this really rare clotting disorder, which at this point, doctors are very aware of and are going to be much better at picking up faster,” says Linkins.
This is also not the time to be picky. Gardam says people who are opting to wait for Pfizer or Moderna may not have the option depending on supply. “It may be that you don’t get vaccinated until July or August, but between now and then, you could have picked up COVID,” he explains.
Both Linkins and Gardam encourage you to speak to your healthcare provider if you’re still apprehensive after looking at the facts.