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2021 COVID-19 Science Vaccine

New Clotting Disorder Caused by Vaccine

We’ve already discussed the rare clotting disorder associated with COVID-19 vaccinations, resulting in the pause of the Janssen vaccine last month.  It’s time to take a deeper dive to understand more about this disorder. To start, we must learn a little about platelets. It’ll be quick, I promise.

Platelets are bits of cells that circulate in the blood stream looking for leaks.  When a leak is found, platelets are activated and clump together to plug the hole.  There are lots of platelets in blood, so one hole usually isn’t enough to reduce the platelet count.  However, if all the platelets are activated at once, many clumps form, and the count of platelets goes down dramatically.  The reduction of platelet count is called thrombocytopenia. “Thrombocytes” means “platelets” and “penia” means “not enough”, so “thrombocytopenia” simply means “not enough platelets”.

Heparin induced thrombocytopenia (HIT) is a condition in which platelets are activated after the use of heparin, causing a suddenly drop in platelet count.  This is particularly dangerous because, as you may recognize, heparin is a “blood thinner” given to dissolve clots.  The formation of many clots is the opposite of what is desired.  HIT occurs because of an immune response in which antibodies to a molecule that forms when heparin is injected cause activation of platelets throughout the body.  The molecule is called “heparin-platelet factor 4 complexes,” but the name doesn’t matter. Most people don’t have those antibodies to this molecule.  This is a rare but life-threatening complication of heparin therapy.

The rare clotting disorders that have been rarely been observed after the Janssen vaccine have a similar mechanism.  Now referred to as vaccine induced thrombotic thrombocytopenia (VITT), it is like HIT because antibodies develop after vaccine administration that cause platelet activation.  The antibodies are similar enough to HIT antibodies that giving heparin will make the clots worse.  This is why heparin cannot be used to break down those clots.  

This seems to be the same clotting complication that has been observed with the AstraZeneca COVID-19 vaccine, not available in the U.S., but widely available elsewhere.  Both vaccines have in common the use of an adenovirus vector to deliver the vaccine.  A viral vector is not used in the mRNA vaccines. Is VITT related to the adenovirus vector in some vaccines? Nobody knows for sure. Yet.

This is another example of unintended consequences resulting from the use of systems still in the early stages of development.  Life is full of risks; we accept that.  But wisdom demands that risks be acknowledged, quantified, and mitigated as much as possible.  Only the foolish follow science blindly.

By Kevin Homer, MD

Kevin Homer has practiced anatomic and clinical pathology at a community hospital in Texas since 1994.

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