By Maggie Fox, CNN
(CNN) – Doctors say they are targeting the cause of blood clots that may be related to certain coronavirus vaccines, and said their findings have important implications for the treatment of the condition, regardless of whether vaccines cause it.
While the link is not yet firm, they call the condition vaccine-induced immune thrombotic thrombocytopenia, or VITT. It is characterized by unusual blood clotting in combination with a low number of blood clotting cells called platelets. Patients suffer from dangerous blood clots and sometimes they bleed at the same time.
It is most closely associated with the AstraZeneca coronavirus vaccine, which is widely used in Europe and the UK.
The U.S. Centers for Disease Control and Prevention and the Food and Drug Administration are checking to see if Johnson & Johnson’s Janssen vaccine can also cause the blood clots. Both the AstraZeneca vaccine and the J&J vaccine use cold viruses called adenoviruses as carriers, and some experts suspect that the body’s response to those viral vectors underlies the response. AstraZeneca’s vaccine is not authorized in the US.
The FDA and CDC have requested a pause from providing the J&J vaccine during their investigation.
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 antibody response. These so-called anti-PF4 antibodies had only previously been seen as a rare response to the use of the common blood thinner heparin.
The findings support a theory that an immune response may underlie the rare blood clots, but the findings don’t explain it yet, Scully and colleagues reported in the New England Journal of Medicine Friday. What may be going on is a reaction of the immune system with platelets to cause uncontrolled clotting.
If vaccines cause it, it’s still very rare and uncommon, 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 following vaccination against SARS-CoV-2 do not appear to exceed the background 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 rare, and until further analysis is done it is difficult to predict who may be affected. Symptoms developed more than five days after the first vaccination dose, ”she added.
“In all cases reported to date, this syndrome of thrombocytopenia (low platelet count) and venous thrombosis (blood clot) appears to be caused by receiving the first dose of the (AstraZeneca) ChAdOx1 nCoV-19 vaccine. Although there have been a few reports of patients with symptoms consistent with this clinical syndrome after receiving other vaccines against SARS-CoV-2, they have not yet been confirmed to meet the diagnostic criteria, ”she added.
But if vaccination can cause the condition, it would be important to recognize that and treat it appropriately – because the usual treatment of blood clots is not recommended for VITT.
Patients should receive anticoagulants but not heparin, and infusions of 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 commentary. “Most of the patients included in these reports were women under the age of 50, some of whom received estrogen replacement therapy or oral contraceptives. A remarkably high percentage of patients had thrombosis in unusual places, ”they wrote.
Some European countries have imposed restrictions on who can receive the AstraZeneca vaccine. For instance. Belgium limits its use in people under 55 years of age. Other countries have discontinued its use. The CDC’s vaccine advisers 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 US.
Although blood clots in the brain have received most of the attention, patients have also had blood clots in other large veins and arteries.
These blood clots in the brain – called cerebral sinus vein thrombosis or CVST – are dramatic on their own, but the clots can form elsewhere as well.
Doctors are advised to run tests if people develop blood clots after having recently been vaccinated against the coronavirus, and not to use heparin to treat the blood clots until VITT has been ruled out.
The condition is very similar to a known development called heparin-induced thrombocytopenia, the American Society of Hematology says new guidelines were released earlier this week. It also calls the condition VITT.
ASH published guidelines stating that normal malaise, headache and fever after vaccination are of no concern.
“Patients with severe, recurring or persistent symptoms, especially severe headache, abdominal pain, nausea and vomiting, vision changes, shortness of breath and / or leg pain and swelling, which are either persistent or start four to twenty days after vaccination,” urgently by a medical care provider and attention to the underlying VITT ”, says ASH in the new guideline.
“While current information links VITT to AstraZeneca and Johnson & Johnson vaccines, patients with suggestive timing and symptoms following a COVID-19 vaccine should be evaluated for VITT.”
CDC’s Advisory Committee on Immunization Practices has scheduled a meeting for April 23 to re-examine the matter, after being denied a decision on Wednesday. A committee member told CNN that more data is needed.
“We need to know how big the problem is,” said Dr. Kevin Ault, professor and department director at the University of Kansas Medical Center. “So we’re going to shake things up in the databases that the CDC has and we also need to know what the denominator is – is it just young women or the entire population that’s been vaccinated?”
The CDC wants to know if there is anything specific that puts people at higher risk of developing blood clots after vaccination.
“There are still a fair number of people in the United States who have been vaccinated in the past two weeks,” Ault said. “We saw these responses within two weeks, so it doesn’t sound like a very long time, but we have a fair amount of data in just those nine or ten days.”
In a letter to the New England Journal of Medicine, scientists at Janssen, the vaccine division of Johnson & Johnson, say there isn’t enough evidence to show that the company’s Covid-19 vaccine is causing the blood clots, and they are working closely together with experts. and regulators to review the data, and we support open communication of this information to healthcare providers 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.”
Vaccines made by Moderna and Pfizer / BioNTech use a different technology that sends genetic material packaged in lipids into the body, and they have not been linked to blood clots.
The-CNN thread
™ & © 2021 Cable News Network, Inc., a WarnerMedia company. All rights reserved.