April 6, 2021 | News | Living with MS MS Research

The AstraZeneca vaccine: the A-Z of the problem

The past few weeks have seen considerable controversy about the AstraZeneca vaccine, approved in Canada on February 26, 2021. Unfortunately, the questions surrounding this vaccine can spill over to other COVID vaccines, prompting some to question whether they want to get vaccinated at all.

So let’s review some of the issues behind some of the conflicting information you may have read.

Is it worthwhile getting vaccinated at all?

Vaccination is the best way to protect yourself against COVID. Just over 1 million people in Canada have been infected and over 23,000 people have died. While people with MS do not appear to have a higher risk of contracting COVID overall, many people living with MS do have a higher risk of severe COVID. Those risks are the same as those for the general population: if you are older, have disabilities or other medical conditions (e.g. heart disease, lung disease, obesity), there is a much higher risk of being hospitalized or dying due to COVID.

A COVID infection does not appear to trigger MS relapses. But it can leave you feeling that your MS symptoms are worse. We also do not know what the long-term effects of COVID infection will be, so it is best to do everything possible to avoid infection.

What is the risk of blood clots with the AstraZeneca vaccine?

Some medications are known to be associated with the formation of blood clots that can block blood vessels in the legs (called deep-vein thrombosis) or the lung (called a pulmonary embolism). For example, clots can occur in women who take oral contraceptives. The risk (depending on the formulation) of clotting may be as high as 1 in a 1,000 in a given year (or about 1% if you take them for 10 years).

The clotting disorder that has been linked with the AstraZeneca vaccine is something different. It is a very rare type of clotting that develops differently. It appears to primarily affect the veins that drain the brain, causing a condition called CVST (or central venous sinus thrombosis). In the United Kingdom, there have been at least 5 reports of this type of clot among the 11 million people who have been vaccinated. More cases have been reported in Europe: about 7 cases among the 20 million people vaccinated.

This suggests the risk in the UK is about 1 in 2 million. However, German researchers have estimated that the risk may be as high as 1 in 100,000. Much has been made of the fact that no cases have been seen in Canada – but this is disingenuous. No cases would be expected because so few people in Canada have received this vaccine.

It is important to note that it has not been definitively established that the AstraZeneca vaccine causes this clotting problem. And to put things into perspective, clotting problems can develop because of COVID itself. There are still many unknowns about COVID.

Is there a risk of clots with other COVID vaccines?

People receiving the Janssen vaccine had a higher number of clotting events (not CVST) compared to people taking a placebo (15 cases compared to 10 cases with placebo), which was considered to be a similar rate. But it does show that people may develop clotting problems even if they haven’t received a vaccine. The Pfizer and Moderna vaccines may have had cases but they were not reported.

Is a 1 in 100,000 incidence of CVST an acceptable risk?

Everyone views risk differently. If you are an actuary, you might look at this risk relative to other risks:

The risk of accidentally drowning in a given year is 1.2 in 100,000 (National Safety Council).
The risk of a Canadian women dying during childbirth is 8 in 100,000 (StatsCan).
The risk of a Canadian being diagnosed with MS in a given year is 11 in 100,000 (MS Society).
The risk of a Canadian catching COVID is 2,600 in 100,000 (worldometer,com).
If a Canadian catches COVID, the risk of dying is 60 in 100,000 (worldometer.com).

But how you perceive risk is very much about your perceptions rather than numbers. You may perceive that flying to your destination is riskier than driving, and no amount of statistics will convince you otherwise.

Should I refuse the AstraZeneca vaccine?

At the moment, Canada’s National Advisory Committee on Immunization (NACI) has advised that the vaccine should not be given to people under age 55. This is because most cases of the clotting problem occurred in that age group, but also because there are alternative vaccines available (the Pfizer and Moderna vaccines).

Of course, alternative vaccines are available to older people as well. NACI has stated that people aged 55 years or older can receive the AstraZeneca vaccine – with informed consent. So you are within your rights to refuse to consent to this vaccine if you are uncomfortable with the potential risk, or the idea that you may be facing this risk once again when you get your booster injection. Another worry is that after you get the first injection, the government may change its mind yet again about this vaccine. If the government stopped using the vaccine altogether – unlikely but possible – then you would then need to get a booster shot using a different vaccine, something that health authorities are not currently recommending (this strategy has not been tested although studies are in the works).

If you refuse vaccination with a specific vaccine, this will delay your vaccination date somewhat and prolong the time you are exposed to the risks of COVID-19. So you will need to weigh the pros and cons of that decision.

The COVID has been a time of great uncertainty, vaccine development has been extraordinarily rapid – so it is little wonder that there has been confusion as new information becomes available. But it is important to bear in mind that whatever doubts you may have about the AstraZeneca vaccine, there is no need to hesitate about getting another COVID vaccine. It is very important for people with MS to get vaccinated as soon as they become eligible to protect themselves against COVID-19.

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