Reports recently said that what worried many people four weeks ago is now prominently accepted: That the AstraZeneca COVID-19 vaccine can, in very rare circumstances, result in a disorder characterized by hazardous blood clots and low platelet counts.
Specifically, in Europe, at least 222 suspected COVID-19 cases have been reported among more than 30 million who have been given the first dose of the vaccine. Out of these people, more than 30 deaths have been reported.
Faced with the accruing cases, the European Medicines Association or EMA, acknowledged earlier this month that there is a plausible causal link between the blod clot syndrome and the vaccine called Vaxzevria.
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Medical Staff handles an empty vial of the AstraZeneca vaccine against Covid-19 at a vaccination center at the Messe trade fairgrounds during the third wave of the coronavirus pandemic on April 8, 2021, in Erfurt, Germany.
Link Between Vaxzevria and Blood Clot
As the link turns clearer, Science reported that a probable mechanism is driven by an errant immune response "has come into focus."
Now health officials are facing difficult questions about who should and should not be given Vaxzevria, which some nations have already restricted to older-age populations, upending schedules of vaccinations.
Researchers have emphasized that the troubles do not spell the end of the AstraZeneca COVID-19 vaccine.
In the vast majority of COVID-19 cases, its benefits are outweighing the risks, and the vaccine, described to be inexpensive and easy to store, remains the best hope for getting large numbers of people vaccinated in low- and middle-income nations.
More so, some scientists have suggested that a simple tactic could decrease the danger while stretching supplies: Cut the dose of the vaccine in half.
Adverse Effect
Late last week, some of the first study authors to described the condition in the research entitled "Thrombotic Thrombocytopenia after ChAdOx1 nCov-19 Vaccination," had their observations published in the New England Journal of Medicine or NEJM.
One team described 11 patients in Austria and German and the other observed five patients in Norway. Both research groups discovered that the patients had unusual antibodies that stimulate clotting reactions, which use up the platelets of the body, and can block blood vessels, resulting in possibly fatal strokes or embolisms.
The symptoms are akin to a rare reaction to the drug heparin also known as heparin-induced thrombocytopenia or HIT, in which the immune system is making antibodies to a complex of heparin, as well as a protein known as PF4 or platelet factor, which, as described by the National Library of Medicine, stimulates platelets to form hazardous clots throughout the body. The study investigators also found sickened vaccine recipients had antibodies as well, to PF4.
Vaxzevria Containing Adenovirus Engineered to Infect Cells
In the study, University of Greifswald's Andreas Greinacher, a clotting expert, together with his colleagues, speculate too, about a possible mechanism.
Vaxzevria, the study specified, contains an adenovirus engineered to infect cells and prompt them to produce spike protein of the virus.
Among the approximately 50 billion virus particles in every dose of the vaccine, explained Greinacher, some may break apart and release their DNA.
DNA, like heparin, is said to be negatively charged, which would help attach it to PF4, which has a positive charge.
This complex might stimulate the antibodies' production, especially when the immune system is already on high alert due to the vaccine.
The immune response to extracellular DNA, the expert continued explaining, is part of an olden immune defense activated by severe injury or infection. The DNA itself can instruct the body to raise blood coagulation.
Alternatively, the study said, may have already existed in the patients and the vaccine may just enhance them. According to Duke University School of Medicine hematologist, Gowthami Arepally, a lot of people harbor such antibodies as protection from PF4, although they are kept in check by an immune mechanism also called peripheral tolerance
Arepally, who works as an external consultant with AstraZeneca on this issue added that when one gets vaccinated, sometimes, the peripheral tolerance's mechanisms get disturbed.
And when that takes place, the hematologist explained, does that unleash any autoimmune disorders that an individual is predisposed to, perhaps, like HIT.
Related information about the link between AstraZeneca COVID-19 vaccine and blood clotting is shown on CNBC International TV's YouTube video below:
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