COVID-19 vaccines from AstraZeneca and Johnson & Johnson have triggered potentially deadly blood clots. Many countries including the U.S., Norway, and Denmark have either temporarily paused or halted the distribution of these vaccines altogether.
According to the latest news reports, the Centers for Disease Control and Prevention said there have been at least 28 confirmed cases of these rare blood clots out of the 8.73 million doses of the Johnson & Johnson vaccine administered in the U.S. These reported cases occurred in those who got the shot before the Food and Drug Administration paused the use of the vaccine April 13. The pause was lifted April 23.
Professor Eric van Gorp, from Erasmus University in the Netherlands, is one of the many scientists investigating the cause of the clots.
"Understanding the cause is of highest importance for the next generation vaccines, because the novel coronavirus will stay with us and vaccination will likely become seasonal," he said, according to The Wall Street Journal.
The rare side effect, called cerebral venous sinus thrombosis (CVST), occurs when clots prevent blood from draining from the brain. According to The Guardian, the clotting disorder is accompanied by low platelet counts, and most cases have been CVST related. The death rate is high.
A study in Norway and a second review which examined patients in Austria and Germany, suggested that the rare clotting experienced after the COVID-19 vaccines resembles a condition seen in patients who are treated with the blood thinner, heparin.
The studies so far indicate blood clots occur in people with high levels of antibodies to platelet factor 4, or PF4. While this does not explain why the vaccines could trigger this reaction, it does give a clue about what is happening in the body and what to look for to potentially avoid it in the future, according to STAT.
But one group of researchers is exploring a possible theory that might explain why blood clotting is triggered by COVID-19 vaccines. German scientists led by Professor Andreas Greinacher at the University of Greifswald said they believe the Johnson & Johnson and AstraZeneca vaccines that both use adenovirus technology to neutralize COVID-19 cause an over activation of blood platelets.
The inflammation caused by the vaccines, coupled with PF4, could trick the immune system into believing it is being attacked by bacteria. This might prompt a defense mechanism where the immune system goes haywire and causes clotting and bleeding, according to the Journal.
Greinacher, a hematologist, compares the response to "awakening a sleeping dragon." The professor also noted the preservative called EDTA which is used in the vaccines to help proteins travel in the bloodstream might also contribute to the clotting.
Other researchers globally have confirmed his findings, but more investigation is needed to determine how to identify and prevent the aberrant clotting in certain individuals. Greinacher and his team have already received doses of the Johnson & Johnson vaccine to study.
"We strongly support raising awareness of the signs and symptoms of this very rare event, and we are currently exploring a potential collaboration with Dr. Greinacher," said a Johnson & Johnson spokesperson, according to the Journal.
And Greinacher said the vaccines should not be shelved despite the incidences of blood clotting.
"COVID-19 is much, much more dangerous than this extremely rare condition," he stated.
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