EXPLAINER: What’s recognized about COVID vaccines and uncommon clots

Well being authorities are investigating extremely uncommon blood clots after use of two COVID-19 vaccines, and a uncommon immune response is the primary suspect

The U.S. advisable that states pause giving the J&J vaccine on Tuesday whereas authorities look at six stories of the weird clots, together with a dying, out of greater than 6.8 million Individuals given the one-dose vaccination to this point.

However the small variety of circumstances sparked concern as a result of simply final week, European authorities stated related clots have been presumably linked to the AstraZeneca vaccine, which isn’t but OK’d within the U.S. That led some nations to restrict its use to sure age teams. Additionally Tuesday, J&J delayed its imminent European rollout.

These are usually not typical blood clots. They’re bizarre in two methods.

First, they’re occurring in uncommon components of the physique, akin to veins that drain blood from the mind. Second, these sufferers even have abnormally low ranges of platelets — cells that assist kind clots — a situation usually linked to bleeding, not clotting.

Scientists in Norway and Germany first raised the likelihood that some individuals are experiencing an irregular immune system response to the AstraZeneca vaccine, forming antibodies that assault their very own platelets. That’s the speculation because the U.S. now investigates clots in J&J vaccine recipients, Dr. Peter Marks, the Meals and Drug Administration’s vaccine chief, stated Tuesday.

The primary clue: A extensively used blood thinner named heparin typically causes a really related facet impact. Very hardly ever, heparin recipients kind antibodies that each assault and overstimulate platelets, stated Dr. Geoffrey Barnes, a clot knowledgeable on the College of Michigan.

“It form of could cause either side of the bleeding-clotting spectrum,” Barnes stated. As a result of heparin is used so typically in hospitals, that response is one thing “that each hospital in America is aware of the right way to diagnose and deal with.”

There are also extremely uncommon stories of this bizarre clot-low platelet mixture in individuals who by no means took heparin, akin to after an an infection. These unexplainable circumstances haven’t gotten a lot consideration, Barnes stated, till the primary clot stories popped up in some AstraZeneca vaccine recipients.

Well being officers stated one cause for the J&J pause was to ensure medical doctors know the right way to deal with sufferers suspected of getting these clots, which incorporates avoiding giving heparin.

The Facilities for Illness Management and Prevention later Tuesday supplied recommendation on the right way to spot and deal with the weird clots.

In two research within the New England Journal of Drugs final week, analysis groups from Norway and Germany discovered platelet-attacking antibodies within the blood of some AstraZeneca vaccine recipients who had the unusual clots. The antibodies have been just like these discovered with the heparin facet impact though the sufferers had by no means used that blood thinner.

It’s not but clear if there’s an identical hyperlink to the J&J vaccine. However the J&J and AstraZeneca vaccines, in addition to a Russian COVID-19 vaccine and one from China, are made with the identical expertise. They prepare the immune system to acknowledge the spike protein that coats the coronavirus. To try this, they use a chilly virus, referred to as an adenovirus, to hold the spike gene into the physique.

FDA’s Marks wouldn’t say if the bizarre clots could also be widespread to those so-called adenovirus-vector vaccines. Along with the AstraZeneca knowledge, J&J makes an Ebola vaccine the identical approach and he stated authorities would look at “the totality of the proof.”

Probably the most extensively used COVID-19 vaccines within the U.S. — from Pfizer and Moderna — are made with a totally totally different expertise, and the FDA stated there isn’t a signal of an identical clot concern with these vaccines.

What about folks anxious as a result of they acquired the J&J vaccination? Marks stated it is necessary to not confuse the uncommon clot threat with regular flu-like signs folks typically really feel a day or two after a COVID-19 vaccination. He stated regarding signs, akin to extreme headache or extreme stomach ache, would happen per week to a few weeks after the J&J vaccine.


The Related Press Well being and Science Division receives help from the Howard Hughes Medical Institute’s Division of Science Training. The AP is solely liable for all content material.

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