By Maggie Fox, CNN
(CNN) – Doctors say they are studying the cause of blood clots that may be related to certain coronavirus vaccines and said their findings have important implications for treating the disease, regardless of whether the vaccines cause it.
Although the link is not yet strong, it is called vaccine-induced immune thrombotic thrombocytopenia or VITT. It is characterized by an unusual blood clotting combined with a low number of blood clotting cells called platelets. Patients suffer from dangerous clots and sometimes bleeding at the same time.
It has been most closely related to the AstraZeneca coronavirus vaccine, which is widely used in Europe and the UK.
U.S. Centers for Disease Control and Prevention and the Food and Drug Administration are checking to see if the Johnson & Johnson Janssen vaccine can also cause blood clots. Both the AstraZeneca vaccine and the J&J vaccine use common cold viruses called adenoviruses as a carrier, and some experts suspect that the body’s response to these viral vectors could be the basis for the reaction. AstraZeneca vaccine is not authorized in the US.
The FDA and CDC have asked for a break to administer the J&J vaccine while they investigate.
A team led by Dr Marie Scully, a haematologist at University College London Hospitals, studied 22 patients who developed the syndrome after receiving the AstraZeneca vaccine and found they had an unusual antibody response. These so-called anti-PF4 antibodies had only previously been seen as a rare reaction to the use of common blood thinner heparin.
The findings support the theory that an immune reaction could be at the root of rare blood clots, but the results do not yet explain it, Scully and colleagues reported in the New England Journal of Medicine Friday. What may be happening is a reaction of the immune system with platelets to cause uncontrolled clotting.
If vaccines cause it, it is still very rare and unusual, they wrote. It may not even happen more often in recently vaccinated people than in the general population.
“The risk of thrombocytopenia and the risk of venous thromboembolism after SARS-CoV-2 vaccination do not appear to outweigh the underlying risks in the general population, a finding consistent with the rare and sporadic nature of this syndrome.” they wrote. .
“The events reported in this study appear to be infrequent and, until further analysis is performed, it is difficult to predict who may be affected. The symptoms developed more than five days after the first dose of vaccine, “they added.
“In all cases reported so far, this syndrome of thrombocytopenia (low platelet count) and venous thrombosis (blood clot) appears to be triggered by the reception of the first dose of the vaccine (AstraZeneca) ChAdOx1 nCoV-19. While there have been some reports of patients with symptoms consistent with this clinical syndrome after receiving other SARS-CoV-2 vaccines, none have yet been confirmed to meet the diagnostic criteria, ”they added.
But if vaccination can cause the disease, it would be important to recognize and treat it properly, as regular treatment of blood clots for VITT is not recommended.
Patients should receive anticoagulant medications, but not heparin, and infusions of a blood product called intravenous immunoglobulin can replace depleted platelets.
Nor is it clear who is most at risk, Dr. Douglas Cines of the University of Pennsylvania and Dr. James Bussel of Weill Cornell Medicine wrote in a comment. “Most of the patients included in these reports were women under the age of 50, some of whom were receiving estrogen replacement therapy or oral contraceptives. A remarkably high percentage of patients had thrombosis in unusual locations,” they wrote.
Some European countries have restricted who should receive the AstraZeneca vaccine. For example. Belgium limits its use to people under 55 years of age. Other countries have stopped using it. CDC vaccine advisors have been asked to consider whether similar restrictions might be appropriate for the Johnson & Johnson vaccine, although only a handful of cases have been reported in the U.S.
Although blood clots in the brain have received more attention, patients have also had clots in other large veins and arteries.
These blood clots in the brain, called cerebral sinus thrombosis or CVST, are dramatic on their own, but clots can also form elsewhere.
Doctors are advised to test if people develop blood clots after they have recently been vaccinated against coronavirus and not to use heparin to treat the clots until VITT is ruled out.
The condition is very similar to a known development called heparin-induced thrombocytopenia, according to the American Society of Hematology, which has published a new guide earlier this week. It is also called VITT in the condition.
Guidelines published by ASH say normal discomfort after vaccination, headache and fever are not a concern.
“Patients with severe, recurrent or persistent symptoms, especially severe headache, abdominal pain, nausea and vomiting, changes in vision, difficulty breathing and / or pain and inflammation of the legs, which persist or start four to 20 days after vaccination. urgently by a medical provider and the underlying VITT is taken into account, “ASH says in the new guide.
“Although current information links VITT to AstraZeneca and Johnson & Johnson vaccines, patients with suggestive timing and symptoms after any COVID-19 vaccine should be evaluated for VITT.”
The CDC Advisory Committee on Immunization Practices has scheduled a meeting for April 23 to resume the issue after declining decision-making on Wednesday. A committee member told CNN more data is needed.
“We need to know what the size of the problem is,” said Dr. Kevin Ault, a professor and division director at the University of Kansas Medical Center. “So we’re going to shake up the CDC database trees and we also need to know what the denominator is: have only young women or the entire population been vaccinated?”
The CDC wants to know if there is anything specific that could put people at risk of developing blood clots after vaccination.
“There are still a good number of people in the United States who have been vaccinated in the last two weeks,” Ault said. “We’ve seen these reactions in two weeks, so it doesn’t seem very long, but we’ll have a good amount of data in just those nine or ten days.”
In a letter to the New England Journal of Medicine, scientists at Janssen, Johnson & Johnson’s vaccination group, say there is not enough evidence to show that the company’s Covid-19 vaccine causes blood clots and that they are “working closely with experts and regulators to evaluate the data, and we support the open communication of this information to health professionals and the public ”.
“At this time,” they write, “the evidence is not sufficient to establish a causal relationship between these events and the Ad26.COV2.S vaccine.”
Vaccines manufactured by Moderna and Pfizer / BioNTech use a different technology that sends genetic material to the body wrapped in lipids and have not been linked to blood clots.
The-CNN-Wire
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