The virus that causes COVID-19 inflames blood vessels and therefore increases the risk of blood clots forming. The result, an increased risk from COVID-19 of heart attacks, strokes (death of a part of the brain because the blood supply has been cut off by the clot) and pulmonary emboli (clots blocking the circulation to the lungs, robbing the body of oxygen).

There have been reports of clotting from the Oxford-AstraZeneca and Johnson & Johnson (Janssen) COVID-19 vaccines. Instead of inflammation triggering clotting, it appears in these cases that the body is creating antibodies against itself, specifically against a platelet factor. Platelets are small plugs that circulate in the blood stream to close off leaks. When this factor is attacked by the antibodies, the platelets clump together without a leak to plug.

The result can be a blockage of the blood supply to a part of the body and the symptoms will depend on the location of that blockage. If it’s a blood vessel draining the veins in the brain, the resulting cerebral venous sinus thrombosis triggers a headache, change in vision, etc. If it’s in the belly, the result is abdominal pain there; in a blood vessel in the leg, pain and sometimes a change in sensation there; in the lungs, chest pain and shortness of breath.

As the clots are forming they use up platelets, so the number of platelets in the circulation drops. As a result, areas where the platelets really are needed to plug up holes don’t have them, therefore people with this problem can be bleeding in one area while clots are forming where they don’t belong. This is V.I.P.I.T. or “Vaccine Induced” (triggered by the vaccine); “Prothrombotic” (making clots); Immune” (mediated by our immune system, the antibodies created by mistake against our own platelet factor); “Thrombocytopenia” (low platelet count).

The good news is that this is a rare complication of the AZ and J+J adenovirus-based vaccines — much lower than the risk of the complications from COVID-19, which they both protect us from. Furthermore, this has not been seen with the two other vaccines we are also using, the Moderna and Pfizer Bio-NTech vaccines. This makes sense because these vaccines do not use an adenovirus (a modified cold virus) to give your body the information to protect itself. They both use the mRNA blueprint for the spike protein in an envelope of lipid, which is a completely different type of vaccine.

How concerned should we be by V.I.P.I.T? First: it’s rare; and second, we know the population at greatest risk as well as how to diagnose and treat it, so by restricting the use of the adenovirus-based vaccines to people over the age of 55, we can reduce the danger even more.

By trying to be as transparent as possible, we see the data as it appears without an opportunity for in-depth analysis and proper perspective. For comparison, the oral contraceptive is known to increase the risk of blood clots to approximately 3 to 9 per 10,000 women using it, a rate far higher than what we are seeing with the vaccine.

We would not consider withholding the oral contraceptive from someone as long as they understood the risk, minimized it by not smoking and taking other precautions and were aware of the warning signs and what to do about them. Given the seriousness of COVID-19, shouldn’t we be following the same logic?

Dr. Mitch Shulman is an Associate Professor in the Department of Emergency Medicine at McGill Medical School as well as an Attending Physician in the Emergency Department of the McGill University Health Centre. He’s also the CJAD AM 800 Medical Consultant.

(1) comment

Bianca Lallitto

These blood clots have been associated with the Pfizer and Moderna vaccines. The rate of cerebral venous thrombosis per million people for Pfizer and Moderna is 4.1 vs. 5 for AstraZeneca, while the rate of portal vein thrombosis is 44.9 for Pfizer and Moderna vs. 1.6 for AstraZeneca. Just because these incidences of blood clots associated with Pfizer and Moderna aren't being widely reported doesn't mean they aren't occurring.

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