(CNN) – Doctors say they are thinking about the cause of blood clots that could be linked to certain coronavirus vaccines, adding that their findings have important implications for treating the condition, regardless of whether vaccines cause it.
Although the link is not yet fixed, they mention the condition caused by vaccine-induced thrombotic 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 blood clots and sometimes bleeding at the same time.
It is 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 investigating whether Johnson & Johnson’s Janssen vaccine could 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 the virus vectors may underlie the reaction. The AstraZeneca vaccine has not been approved in the US.
The FDA and CDC have called for the suspension of the J&J vaccine while they investigate.
A team led by dr. Marie Scully, a hematologist at University College London, 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 have only recently been seen as a rare response to the use of regular blood-thinning heparin.
The findings support a theory that an immune response may underlie the rare blood clots, but the findings do not yet explain it, Scully and colleagues reported in the New England Journal of Medicine on Friday. What is possibly going on is a reaction by the immune system with platelets to cause uncontrolled clotting.
If vaccines cause it, it is still very rare and unusual. This may not even happen more frequently in people who have recently been vaccinated than among 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 background risks in the general population, a finding consistent with the rare and sporadic nature of this syndrome, “they write. .
‘The events reported in this study appear to be rare, and until further analysis is carried out, 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 caused by receiving the first dose of the (AstraZeneca) ChAdOx1 nCoV-19 vaccine. Although there have been some reports of patients with symptoms consistent with this clinical syndrome after receiving other vaccines against SARS-CoV-2, it has not yet been confirmed that they meet the diagnostic criteria, ‘they added.
But if vaccination can cause the condition, it is important to recognize it and treat it properly – because the usual treatment for blood clots is not recommended for VITT.
Patients should be given anticoagulants but not heparin, and infusions of a blood product called intravenous immunoglobulin may replace the depleted platelets.
It is also not clear who has the greatest risk, said dr. Douglas Cines of the University of Pennsylvania and dr. James Bussel of Weill Cornell Medicine wrote in a commentary. ‘Most 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 restricted who should get AstraZeneca’s vaccine. For example. Belgium restricts its use among people under 55 years of age. Other countries have discontinued use. CDC’s vaccine advisors have been asked to consider whether similar restrictions apply to the Johnson & Johnson vaccine, although only a handful of cases have been reported in the US.
While blood clots in the brain received the most attention, patients also clotted in other large veins and veins.
These blood clots in the brain – called cerebral venous sinus thrombosis or CVST – are dramatic on their own, but the blood clots can also form elsewhere.
Doctors are advised to perform tests if people get blood clots after being recently vaccinated against coronavirus, and not to use heparin to treat the blood clots before excluding VITT.
The condition is very similar to a well-known development called heparin-induced thrombocytopenia, says the American Society of Hematology new guidelines released earlier this week. It also calls the condition VITT.
ASH has published guidelines that normal malaise, headaches and fever after vaccination are not of concern.
‘Patients with severe, recurrent or persistent symptoms, especially intense headache, abdominal pain, nausea and vomiting, vision changes, shortness of breath, and / or leg pain and swelling, should continue or start four to 20 days after vaccination. urgently given by a medical provider and consideration to underlying VITT, ‘says ASH in the new guidance.
“Although current information links VITT to AstraZeneca and Johnson & Johnson vaccines, patients with suggestive timing and symptoms following 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 reconsider the question after it failed to make a decision on Wednesday. One committee member told CNN more information is needed.
“We need to know the magnitude of the problem,” said Dr. Kevin Ault, professor and divisional director at the University of Kansas Medical Center. “So we’re going to shake the trees 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 has been vaccinated?”
CDC wants to know if there is anything specific that could put people at risk of getting 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 reactions within two weeks, so it does not sound very long, but we will have a fair amount of data within nine or ten days.”
In a letter to the New England Journal of Medicine, scientists from Janssen, the vaccine arm of Johnson & Johnson, say there is not enough evidence to show that the company’s Covid-19 vaccine causes the blood clots and that they ‘ work closely with experts. and regulators to assess the data, and we support the open communication of this information to healthcare professionals and the public. ”
“At present, ‘evidence is insufficient to establish a causal link between these events and the Ad26.COV2.S vaccine,'” they write.
Vaccinations made by Moderna and Pfizer / BioNTech use a different technology that sends genetic material into lipids wrapped in lipids, and it is not linked to blood clots.
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