A rare and baffled immune response is the main suspect, as authorities are investigating highly unusual blood clots after the use of two similar COVID-19 vaccines by Johnson & Johnson and AstraZeneca.
The US recommends them states pause to give J&J vaccine on Tuesday, while authorities examine six reports of unusual clots, including death, of more than 6.8 million Americans who have received the one-dose vaccine so far .
But the small number of cases caused concern because just last week, European authorities said that possibly similar clots were related to the AstraZeneca vaccine, which is not yet good in the United States, which led some countries to limit it. use in certain age groups.
Also on Tuesday, J&J delayed its imminent European deployment.
WHAT DOES THESE COLLEGES DO?
They are not typical blood clots. They are strange in two ways.
First, they occur in unusual parts of the body, such as veins that drain blood from the brain. Second, these patients also present with abnormally low levels of platelets (cells that help form clots), a condition that is usually related to bleeding rather than clotting.
Scientists in Norway and Germany first raised the possibility that some people may experience an abnormal immune system response to the AstraZeneca vaccine, forming antibodies that attack their own platelets. That’s the theory the United States is now investigating clots in J&J vaccine recipients, Dr. Peter Marks, head of vaccines at the Food and Drug Administration, said Tuesday.
WHY SUSPECT THE IMMUNE RESPONSE?
The first clue: a widely used blood thinner called heparin sometimes causes a very similar side effect. Very rarely, heparin receptors form antibodies that attack and overstimulate platelets, said Dr. Geoffrey Barnes, a clot expert at the University of Michigan.
“It can cause both sides of the bleeding coagulation spectrum,” Barnes said.
Because heparin is so often used in hospitals, this reaction is something “that all hospitals in America know how to diagnose and treat.”
There are also incredibly rare reports of this strange combination of platelets with low clots in people who never took heparin, such as after an infection. These unexplained cases have not attracted much attention, Barnes said, until the first reports of clots appeared on some AstraZeneca vaccine recipients.
Health officials said one of the reasons for J&J’s break was to make sure doctors know how to treat patients suspected of having these clots, which includes avoiding heparin.
Centers for Disease Control and Prevention later offered advice on how to detect and treat unusual clots on Tuesday.
WHAT DOES THE RESEARCH SHOW?
In two studies published in the New England Journal of Medicine last week, research teams in Norway and Germany found antibodies that attacked platelets in the blood of some AstraZeneca vaccine receptors that had strange clots. The antibodies were similar to those found with the side effect of heparin, although patients had never used this anticoagulant.
It is not yet clear if there is a similar link to the J&J vaccine. But the J&J and AstraZeneca vaccines, as well as a Russian COVID-19 vaccine and one from China, are made with the same technology. They train the immune system to recognize the spike protein that coats the coronavirus. To do this, they use a cold virus, called an adenovirus, to carry the ear gene to the body.
FDA marks would not say whether the strange clots may be common to these so-called vector vaccines against adenovirus. In addition to AstraZeneca data, J&J makes an Ebola vaccine in the same way and said authorities would examine “all of the evidence.”
WHAT ABOUT OTHER VACCINES?
The most widely used COVID-19 vaccines in the United States (from Pfizer and Modern) are made with a completely different technology, and the FDA said there are no similar signs of concern for the clot with these vaccines.
What about people worried about getting the J&J vaccine? Marks said it’s important not to confuse the rare risk of a clot with normal flu-like symptoms that people often feel a day or two after the COVID-19 vaccine. He said symptoms, such as severe headache or severe abdominal pain, would occur one to three weeks after the J&J vaccine.
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The Associated Press Health and Science Department is supported by the Howard Hughes Medical Institute’s Department of Science Education. The AP is solely responsible for all content.