The rare cases in which the Oxford and AstraZeneca vaccine has caused blood clots appear to respond to an erroneous response from the immune system. A study in the laboratory has shown that the viral vector used to inoculate the formulation binds under certain and exceptional conditions to platelets in the bloodstream. This pairing with a foreign agent activates certain antibodies that attack and surround the strange partner, causing an accumulation that degenerates into thrombosis.
With no cases of thrombi during the testing phase, the massive inoculation of millions of people at the beginning of the year revealed a few hundred cases in which those vaccinated had blood clots, some with fatal results. The former occurred after inoculation with the Oxford and AstraZeneca vaccines, but shortly thereafter they were repeated with Janssen’s. Although the European Medicines Agency (EMA) ruled in March that vaccines were not associated with a generalized increase in the risk of blood clots, it did acknowledge then that the medicine “could be associated with very rare cases” of thrombus formation. The EMA ruled that the benefits of the vaccine continued to outweigh the minimal risk.
It wasn’t enough for many scientists and they set about investigating the connection, including members of the teams that designed the vaccines. Now a group of them has published in the magazine Science Advances a probable explanation for those rare thrombi. The work, led by experts from Cardiff University (United Kingdom), Arizona State University and the Mayo Clinic (both in the United States), completely disarmed ChAdOx1, the scientific name of the Oxford and AstraZeneca vaccine, looking for clues . Basically, this vaccine is made up of a recombinant protein that, as if it were that of the virus, activates the defenses, and a viral vector that it uses as transport. In the case of this formulation, the vehicle is an inactivated adenovirus that causes colds in chimpanzees.
What they have found is that this adenovirus and not the vaccine agent itself could be to blame for the thrombi. All the vaccines that are being administered work the same: intramuscular injection, reaching the closest lymphatic tissues. There certain cells of the immune system (T cells), believing it to be a virus, carry it to the ganglia, where it activates the defense system, which is dispersed through the blood. However, sometimes during the injection parts of the vaccine content bypass the process, reaching the bloodstream directly and ending up unleashing a dangerous chain reaction.
As the study authors detail, the adenovirus used as a vector binds to a certain type of platelets (PF4) and everything seems to be a matter of magnetism. Cardiff University professor and study co-author Alan Parker told the BBC News: “Adenovirus has an extremely negative surface [carga eléctrica] and platelet factor 4 is extremely positive and the two fit very well ”.
A matter of polarity
The researchers also studied two other adenoviruses, Ad5 and Ad26, both human, and used in the Janssen and Sputnik V vaccines. There are no known cases of thrombi from the Russian, but it may be due to their scant distribution in western countries and less supervision by health authorities. Of the second, which uses Ad26 as a vector, it was related to a few dozen cases. The study shows that these vectors also attracted PF4s.
For Adolfo García-Sastre, a microbiologist from the Icahn School of Medicine at Mount Sinai in New York (United States), “the connection with viral vectors makes sense, since cases of thrombi have only occurred with these vaccines.” But he clarifies that more studies still need to be done and verified in humans. The study authors conclude that, by modifying these viral vectors, the risk of these cases of thrombi with a marked decrease in platelets (thrombocytopenia) could be reduced. A risk that is already low in itself: according to EMA figures, 300 cases had occurred as of October after the Oxford and AstraZeneca vaccines. And the pharmaceutical company had distributed up to last November 2 billion of its vaccine.
You can follow MATTER on Facebook, Twitter and Instagram, or sign up here to receive our weekly newsletter.
#Cases #thrombi #caused #AstraZeneca #vaccine #linked #erroneous #autoimmune #response