AstraZeneca: Blot Clots apparently Stem From Rare Antibody Reaction

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Sat, 2021-04-10 13:43 — mike kraft

New research has identified unusual antibodies that appear to have caused, in rare cases, serious and sometimes fatal blood clots in people who received the Covid vaccine made by AstraZeneca.

Exactly why the rare reactions to the vaccine occurred is still a mystery.

Scientific teams from Germany and Norway found that people who developed the clots after vaccination had produced antibodies that activated their platelets, a blood component involved in clotting. The new reports add extensive details to what the researchers have already stated publicly about the blood disorder.

Younger people appear more susceptible than older ones, but researchers say no pre-existing health conditions are known to predispose people to the rare reaction. That is worrisome, they say, because there is no way to tell if an individual is at high risk.

Reports of the clots have already led a number of countries to limit AstraZeneca’s vaccine to older people, or to stop using it entirely. These cases have dealt a crushing blow to global efforts to halt the pandemic, because the AstraZeneca shot — easy to store and relatively cheap — has been a mainstay of vaccination programs in more than 100 countries.

The European Medicines Agency, the regulator for the European Union, has emphasized repeatedly that the clotting disorder is rare, and that the vaccine’s benefits far outweigh its risks. But when a side effect has the potential to be devastating or fatal — like the blood clots in the brain linked to this vaccine — some regulators and segments of the public are finding that the risk is unacceptable, even if it is extremely rare. ...

The two new studies were published by The New England Journal of Medicine. One from Germany described 11 patients, including nine women ages 22 to 49. From five to 16 days after vaccination, they were found to have one or more clots. Nine had cerebral venous thrombosis, a clot blocking a vein that drains blood from the brain. Some had clots in their lungs, abdomen or other areas. Six of the 11 died, one from a brain hemorrhage....

One patient had pre-existing conditions that affected clotting. During a news briefing on Friday, Dr. Andreas Greinacher, an author of the report, said those conditions most likely played only a minor role in the reaction that occurred after vaccination.

He also said it was a “likely possibility” that the people who developed the clotting disorder had some rare, unknown biological traits — what he called “individual co-factors” — that predisposed their immune systems to make powerful, misdirected antibodies in response to the vaccine. He called that “good news” for the general population, who do not have the co-factors.

There is “clear evidence” that the AstraZeneca vaccine in rare cases leads the body to make antibodies that activate platelets, and that those antibodies are causing blood clots, Dr. Greinacher said.

But, he added: “We have no way to predict who will develop these antibodies.” ..

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