Researchers in the United Kingdom have conducted a detailed investigation of 22 patients who developed rare yet serious blood clots along with a reduction in blood platelets after receiving a dose of the AstraZeneca-Oxford vaccine, which is now called Vaxzevria.
They found that all patients tested positive for unusual antibodies to a signaling protein called platelet factor 4 that helps the body coordinate blood clotting.
The researchers, who published their findings in the New England Journal of Medicine, said the presence of the antibodies suggests that the vaccines are somehow triggering an autoimmune attack that causes large clots to form that then diminish the supply of platelets in the blood, according to Medscape.
Experts say that the emerging evidence of rare brain blood clot disorder called cerebral venous sinus thrombosis indicates that doctors should remain vigilant and look for any signs or symptoms associated with the disorder.
Dr. James Zehnder of the Stanford University School of Medicine in California, who was not a part of the study, said that the mounting evidence pointing to a “maladaptive immune response” was quite remarkable.
He explained that it is unclear why this syndrome is seen in a small number of people after getting the anticoagulant heparin or a COVID-19 vaccine.
“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 magnitude of it is not known,” said Dr. Zehnder, adding that it will be important to figure out if particular groups of people are at higher risk than others, like young women. “There are many more questions than answers now,” he added.
The researchers said doctors should watch for symptoms such as breathlessness, headaches, dizziness, muscle weakness, abdominal pain, back pain, nausea or vomiting in those who have received the vaccine.
Experts say that all the currently approved COVID vaccines are extremely safe. In fact, they say the risk of developing a life-threatening blood clot is far higher with COVID than with a vaccine, according to Medscape.
Dr. John Wherry of the Institute for Immunology at the University of Pennsylvania in Philadelphia said, “The chances of this happening to you are about between 1 and 100,000 to 1 in 1 million. If you’re an American, the chances of dying from COVID are 1 in 600.”
Dr. Wherry explained that he was surprised to see no cases of blood clots in the clinical trials that involved tens of thousands of people, nothing that these rare events come to light when a vaccine or drug is used in millions.
“We’re doing everything right,” he said. “It’s unfortunate and traumatic if it happens, but in terms of risk to benefit ratio, we still have to put the numbers in perspective and now having caught many of these events, we now have an idea of what to do when we see them.”
As far as the UK cases are concerned, all patients were healthy before developing the rare blood clots and none of them was taking medications linked to blood clotting or bleeding. Some of the patients experienced mild bruising and petechial rashes (tiny red spots).
Experts who are investigating the symptoms in the setting of the new COVID vaccines have called the disorder Vaccine-Induced Thrombotic Thrombocytopenia (VITT). The article was published on Medscape Medical News.
