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New evidence has emerged today linking COVID-19 vaccines to extremely rare cases in people who develop blood clots and low platelets within a few weeks of being vaccinated.
A team of researchers in the UK conducted an in-depth study of 22 patients who developed severe blood clots, combined with a drop in platelets after receiving a dose of AstraZeneca vaccine, now called Vaxzevria. They also tested an additional patient who had clinical signs of a decrease in platelets after vaccination. Almost all of the patients – 22 out of 23 – tested positive for unusual antibodies to platelet factor 4, a signaling protein that helps the body coordinate blood clotting.
The presence of the antibodies indicates that the vaccines somehow cause an autoimmune attack that causes large blood clots to form which then reduces the supply of platelets into the blood.
The study and an editorial on the issues are discussed in the New England Journal of Medicine.
This is at least the third study to explain the presence of these antibodies in patients with blood clots and low platelets after vaccination, and according to doctors, the emerging evidence suggests that doctors should be vigilant for this new syndrome in anyone who has symptoms of experienced blood clots. the body, not just the brain.
James Zehnder, MD, director of the coagulation laboratory at Stanford University School of Medicine in California, said the growing evidence pointing to a ‘maladaptive immune response’ was quite remarkable. He was not involved in the research.
Zehnder says the reason why this syndrome, which appears to be an autoimmune attack on a blood signal protein, develops in a small number of people after receiving the anticoagulant heparin or a vaccine for COVID-19 is still ‘ a mystery.
He says that although the catastrophic cases of large blood clots in parts of the brain where doctors usually do not see it sticking out, he wonders if other, less obvious cases will go unnoticed.
“Then the question is, you know, how much more of this is going on in a more subtle way? And so I think the true extent of it is not known,” he says, noting that it will be important in the coming weeks. and months to find out if specific groups of people are at higher risk than others, such as young women. “There are a lot more questions than answers now,” he says.
Main symptoms to look at
The symptoms you should pay attention to include shortness of breath, headache, dizziness, muscle weakness or abdominal pain, back pain or nausea and vomiting in everyone who is within 3 weeks of their vaccinations, including men.
People who are not vaccinated can also develop this form of blood clots, called cerebral venous sinus thrombosis. These cases – whether they happen after a vaccine or not – are very rare. According to Peter Marks, of the U.S. Food and Drug Administration, there are on average two to 14 cases of blood clots in vessels that draw blood from the brain for every million people.
Doctors say that the vaccines authorized to protect people against the new coronavirus are extremely safe. In fact, the risk of developing a life-threatening blood clot is much higher with COVID than with a vaccine.
“The chances of this happening to you are between 1 and 100,000 to 1 in 1 million,” said John Wherry, PhD, director of the Institute of Immunology at the University of Pennsylvania in Philadelphia. “If you’re an American, the chance of dying from COVID is 1 in 600,” Wherry continued, referring to statistics on American COVID cases and deaths maintained by Johns Hopkins University.
In a submission to the Centers for Disease Control and Prevention this week, representatives of vaccine manufacturer Johnson & Johnson said they had found a 25-year-old man who developed a rare blood clot in his brain and low platelets during their clinical trial. . When they returned and tested his stored blood, they found that he also had the platelet factor 4 antibodies, which made him the 7th case linked to the vaccine in the United States. He has meanwhile recovered.
Investigators initially dismissed his case as unrelated to the vaccine because another study participant, a 24-year-old woman, also developed a similar blood clot in her brain, but she was in the placebo group. She recently prescribed birth control pills, which increase a woman’s risk of blood clots and strokes, such as the kind she suffered.
An eighth case, possibly linked to the Johnson & Johnson vaccine, is still being investigated in the United States.
Wherry said it was not surprising that these rare cases were not detected in the clinical trials involving tens of thousands of people. He said that very rare incidents sometimes only come to light when millions of medicines or devices are used, as the vaccines were now.
He said that the fact that these events were detected at all means that security surveillance systems are working.
“We’re doing everything right,” he said. “It’s unfortunate and traumatic when it happens, but in terms of the risk-benefit ratio, we need to put the numbers into perspective and now, after capturing many of these events, we now have an idea of what to do. as we see it, “Wherery added.
British affairs
Among the 22 cases identified in the new UK study, 16 (70%) were under the age of 50 and 14 (61%) were women. Everyone was healthy before they developed the rare blood clots. No one is taking medicines related to clotting or bleeding. Some came in with light bruises and small red spots called petechiae, indicating bleeding under the skin.
This constellation of symptoms, severe clotting combined with a drop in platelets, is not new. Doctors recognize this as a sign that someone has a severe and rare reaction to the anticoagulant heparin. In patients using heparin, it is called HIT for thrombocytopenia caused by heparin.
Doctors investigating the symptoms in the vicinity of the new COVID vaccines call it thrombotic thrombocytopenia, or VITT, by vaccine.
The UK study authors found that a careful test commonly used to detect HIT – the HemosIL AcuStar HIT IgG test – was often negative for patients with VITT. They say VITT must be confirmed by another type of test, an ELISA or enzyme-linked immunosorbent assay.
Patients with VITT also need a different type of treatment than anyone would normally give to dangerous blood clots or bleeding. For example, donating platelets to stop bleeding can make the situation worse. Instead, they need IVIG treatment to alleviate the apparent autoimmune attack. Researchers say that until more is known, it is also wise to use anticoagulants other than heparin to treat blood clots.
Wherry says he is not surprised to see single men affected, but so far the emerging picture suggests that women are at greater risk.
He says women tend to be more prone to autoimmune diseases and are also more susceptible to blood clots due to the hormone estrogen.
“It therefore joins this idea that it may be an indication of some autoimmune bias,” he said.
NEJM. Published online on April 16, 2021. Full text, editorial
Several co-authors state that they have received personal fees from one or more of the following companies: Bayer, Bristol Myers Squibb, Daiichi Sankyo, Pfizer, Novartis, Octapharma, Sanofi, Sobi, Alexion and Takeda. One co-author reports grants from Shire and Novartis; one co-author reports other financial relationships with GSK; and one co-author reports a patent test for bacterial meningitis based on a blood test, filed for patent pending.
Wherery reports consulting agreements with and / or is a scientific advisor to Merck, Roche, Pieris, Elstar and Surface Oncology. He has a patent license agreement on the PD1 road with Roche / Genentech and is a founder of Arsenal Biosciences.
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