Q. I understand that the vaccine available at pharmacies will likely be the infamous Astra-Zeneca (AZ) one. Since I have had a previous blood clot many years ago, am I safe to get that vaccine and just how commonly does this happen?
A. That is a very good question. To begin answering, let’s review what we know so far. It is true that the only vaccine available from a pharmacy is going to be the Astra Zeneca one, at least until the Johnson & Johnson version is available (which is expected by the end of this month, but that does not necessarily mean it will be accessible immediately, there is always a delay, particularly so in Ontario it seems).
Though it has had its share of bad publicity in recent weeks, it is still considered to be a great option to help us get on our way to a new normal. As has been stated many times, the variants of concern (VOC) are exactly that … a concern, and a big one! They are more transmissible and are proving to be more lethal as well. This has naturally led to more hospital admissions and intensive care wards that are in danger of being over-run.
There is a high-stakes race being run right now in Ontario and around the world. On the one side, there is the rush to vaccinate as many people as possible in order to achieve the goal of herd immunity which should protect those among us who cannot be vaccinated (the very young, the very sick…). In the other lane, are the variants continually mutating into more contagious and toxic forms that, with time, may change into a version that is unaffected by our vaccines or pre-existing antibodies (that are in those among us who were previously infected by COVID-19).
As if on cue, on April 5th, we learned of a possible new variant discovered in Japan (the country that is set to host the summer Olympics in a few short months). This new variant (nicknamed the “Eek” variant) is particularly concerning as it is structurally different enough that the current vaccines may not protect us from it. At this time, this is still strictly speculative as more time and studies will be needed to confirm this. Still, we are in a race for our health, if not our lives. Mutations will only stop when people stop getting infected in massive numbers.
In regards to your blood clot concern, there are a few factors to consider. Firstly, let’s discuss the incidence of blood clots with the AZ vaccine that have been reported as of mid-March. There were about 17 million doses of the AZ administered worldwide and 37 cases of blood clots were reported among them, which equates to a 0.0002% increased risk. It is prudent to mention that there have not been any cases of blood clots associated with the AZ vaccine administered here in Canada to date.
It is important to realize that the prevalence of a venous thrombosis (blood clot), including both deep vein thrombosis and pulmonary thrombosis, in an otherwise healthy person is 0.1% and this risk increases significantly after we turn 45 years old.
Secondly, there are medications that many people take without much thought, despite the fact that these drugs do increase the risk of clotting. Oral contraceptives, also known as birth control pills, are a prime example. Many women take this medication to prevent unwanted pregnancy but some also take it to help regulate periods, reduce symptoms of premenstrual syndrome (PMS) or for chronic conditions such as polycystic ovarian syndrome (PCOS). Women who take these oral contraceptives are 3 to 5 times more likely to experience a blood clot thereby increasing the risk to around 0.3 to 0.5%. Pregnancy is also associated with a 5-fold increase in clotting.
Thirdly, let’s consider some other factors that increase our risk of blood clots that we may not be aware of and likely will not change our habits despite knowing them;
· Travelling increases risk 2-4 times
· Surgery increases risk 2-5 times
· Obesity increases risk 1.7-2.4 times
· Smoking increases risk 1.4-3.3 times
At this point, all of these risks are significantly higher than the risk associated with the AZ vaccine, yet we do not think twice about them. There will likely be a surge in air travel once we are able to travel again and most of us will do so without wasting a moment’s thought about the increased risk of blood clots. That is rational. They very rarely happen. The same appears to be true with the AZ vaccine.
However, as rare as they are, let’s discuss what we do know about them. Though It seems that most cases of the AZ blood clots have involved women less than 55 years of age, it is thought that both men and women are at risk. The statistics show that more women than men have received the AZ vaccine which may explain the increased prevalence in women.
At this point, the risk of blood clots associated with the AZ vaccine does not appear to be more common in people that are already at an increased risk of clotting (see above for some examples). Nor does it seem more prevalent in those who have previously suffered a blood clot or have a family history of such.
The studies of the AZ blood clots seem to indicate that they are a result of either a cerebral venous sinus thrombosis where an obstruction prevents the blood from draining from the brain or a clotting disorder related to very low platelets. That being said, even having a history of low platelets does not seem to increase your risk of having a blood clot with the AZ vaccine.
So, hopefully, this answers your question and if you are 55 years old or older you absolutely should opt to vaccinate yourself against this coronavirus regardless of the vaccine type.
One last point. Blood clots do have tell-tale symptoms before they become dangerous and can be safely treated if they do occur. The signs and symptoms you should be alert for in the 4 to 20 days post vaccination (this is the “at-risk” period so to speak).
· Shortness of breath
· Chest pain
· Leg swelling
· Persistent abdominal pain
· Persistent headache
· Blurred vision
If you experience any of the above symptoms, seek medical help.
Keep in mind that information is evolving with this pandemic and, as it does, science may well change its recommendations on this or any of the other vaccines. That is what rational people do when presented with new information. But for now, the decision to vaccinate oneself should not be as hard as we are making it out to be, even if the only option is the much-maligned AstraZeneca one (which remember is virtually 100% effective at preventing death or the necessity of being treated in an intensive care unit). Get it done as quickly as you can, both for yourself and for your fellow citizens. For more information on this or any other health topic, contact your pharmacist.