By Maggie Fox, CNN
(CNN) – Doctors say it refers to the cause of blood clots that may be linked to certain coronavirus vaccines and said their findings have important implications for how the condition is treated, regardless of whether the vaccines cause it.
Even if the link is not yet firm, they call the state vaccine-induced immune thrombocytopenia or VITT. It is characterized by 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 strongly linked to the AstraZeneca coronavirus vaccine, which is widely used in Europe and the United Kingdom.
The U.S. Centers for Disease Control and Prevention and the Food and Drug Administration are checking to see if the Johnson & Johnson Janssen vaccine could also cause blood clots. Both the AstraZeneca vaccine and the J&J vaccine use common cold viruses called adenoviruses as carriers, and some experts suspect that the body’s reaction to these viral vectors may be the basis for the reaction. The AstraZeneca vaccine is not authorized in the United States.
The FDA and CDC have requested a break in the administration of the J&J vaccine while investigating.
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 that they had an unusual response to antibodies. These so-called anti-PF4 antibodies have only been seen before as a rare reaction to the use of thin common heparin in the blood.
The findings support a theory that an immune reaction may underlie the formation of rare blood clots, but the findings do not yet explain it, Scully and colleagues reported in the New England Journal of Medicine Friday. What can happen is a reaction of the immune system with platelets to cause uncontrolled coagulation.
If vaccines cause it, it is still very rare and unusual, they wrote. It may not happen even more often in people who have recently been vaccinated than in the general population.
“The risk of thrombocytopenia and the risk of venous thromboembolism after vaccination against SARS-CoV-2 do not appear to be higher than 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 seem to be rare and, until further analysis, 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 receiving the first dose of vaccine (AstraZeneca) ChAdOx1 nCoV-19. Although there have been several 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 condition, it would be important to recognize and treat it properly – because regular treatment for blood clots is not recommended for VITT.
Patients should be given anticoagulants, but not heparin, and infusions with a blood product called intravenous immunoglobulin can replace depleted platelets.
It is also unclear 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 places, “they wrote.
Some European countries have restricted who should receive the AstraZeneca vaccine. E.g. Belgium limits its use to people under the age of 55. Other countries have stopped using it. CDC vaccine advisors were 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 United States.
While blood clots in the brain received the most attention, patients also had clots in other large veins and arteries.
These blood clots in the brain – called cerebral venous sinus thrombosis or CVST – are dramatic on their own, but clots can form elsewhere.
Doctors are advised to perform tests if people develop blood clots after being recently vaccinated against coronavirus and not to use heparin to treat clots until VITT has been ruled out.
The condition is very similar to a known development called heparin-induced thrombocytopenia, according to the American Society of Hematology, a new guideline released earlier this week. It is also called the VITT condition.
ASH has issued guidelines saying that normal malaise after vaccination, headache and fever is not a concern.
“Patients with severe, recurrent or persistent symptoms, in particular severe headache, abdominal pain, nausea and vomiting, changes in vision, difficulty breathing and / or pain and swelling of the legs, either persistent or from four to 20 days after vaccination, it must be evaluated urgently by a medical provider and the consideration of the underlying VITT ”, says ASH in the new orientation.
“While current information links VITT to AstraZeneca and Johnson & Johnson vaccines, patients with synchronization and symptoms suggestive of any COVID-19 vaccine should be evaluated for VITT.”
The CDC’s Advisory Committee on Immunization Practices has scheduled a meeting for April 23 to resume the issue, after refusing to make a decision on Wednesday. A committee member told CNN that more data was needed.
“We need to know the size of the problem,” said Dr. Kevin Ault, a professor and division director at the University of Kansas Medical Center. “So we’re going to shake the trees out of the CDC’s databases, and we also need to know who 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 higher risk of developing blood clots after vaccination.
“There are still quite a 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 sound like much, but we’ll have quite a bit of data in those nine or ten days.”
In a letter to the New England Journal of Medicine, scientists at Janssen, Johnson & Johnson’s vaccine arm, say there is insufficient evidence to show that the company’s Covid-19 vaccine causes blood clots to form and “works 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, “there is insufficient evidence to establish a causal relationship between these events and the Ad26.COV2.S vaccine.”
The vaccines produced by Moderna and Pfizer / BioNTech use a different technology that sends genetic material into the body wrapped in lipids and have not been linked to blood clots.
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