Doctors claim they’ve narrowed in on the source of blood clots related to some coronavirus vaccines, and that their results have significant consequences for how to treat the disease, regardless of whether vaccines are to blame.
Vaccine-induced immune thrombotic thrombocytopenia, or VITT, is the name given to the disorder despite the lack of evidence. It’s marked by irregular blood clotting and a low number of platelets, which are blood-clotting cells. Patients are at risk of harmful clots and, in some cases, haemorrhaging.
It’s been strongly related to the AstraZeneca coronavirus vaccine, which is widely used in Europe and the United Kingdom.
The Centers for Disease Control and Prevention (CDC) and the Food and Drug Administration (FDA) are investigating whether Johnson & Johnson’s Janssen vaccine is also causing blood clots. Both AstraZeneca’s and J&J’s vaccines use adenoviruses, which are common cold viruses, as carriers, and some experts believe the body’s response to those viral vectors is to blame. In the United States, AstraZeneca’s vaccine is not approved.
The FDA and the CDC have requested a halt in the distribution of the J&J vaccine while they investigate.
Dr Marie Scully, a haematologist at University College London Hospitals, led a team that looked at 22 patients who acquired the syndrome after receiving AstraZeneca’s vaccine and discovered that they had an unusual antibody response. Anti-PF4 antibodies had only previously been observed as an unusual reaction to the natural blood thinner heparin.
The findings back up a theory that rare blood clots are caused by an immune reaction, but they don’t explain why. Scully and colleagues published their findings in the New England Journal of Medicine on Friday. The immune system may be reacting with platelets, causing uncontrolled clotting.
They wrote that even if vaccines are to blame, it’s still a very rare and uncommon occurrence. It’s possible that it doesn’t happen any more often in newly vaccinated people 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 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 performed, it is difficult to predict who may be affected. The symptoms developed more than five days after the first vaccine dose. In all cases reported to date, this syndrome of thrombocytopenia (low platelet count) and venous thrombosis (blood clot) appears to be triggered by receipt of 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 the receipt of other vaccines against SARS-CoV-2, none have yet been confirmed to fulfill the diagnostic criteria,” they added.
However, if vaccination can cause VITT, it’s critical to consider the condition and handle it accordingly, since the standard treatment for blood clots isn’t recommended for VITT.
Patients should be given anticoagulants but not heparin, and intravenous immunoglobulin infusions can be used to replace platelets that have been reduced.
It’s still unclear who is most at risk. A commentary was written by Dr Douglas Cines of the University of Pennsylvania and Dr James Bussel of Weill Cornell Medicine. “Most of the patients included in these reports were women younger than 50 years of age, some of whom were receiving estrogen-replacement therapy or oral contraceptives. A remarkably high percentage of the patients had thromboses at unusual sites,” they wrote.
Some European countries have imposed restrictions on who is eligible to receive AstraZeneca’s vaccine. As an example. In Belgium, citizens under the age of 55 are not allowed to use it. Other countries have taken a break from using it. While only a few cases have been identified in the United States, the CDC’s vaccine advisors have been asked to consider whether similar restrictions could be necessary for Johnson & Johnson’s vaccine.
While blood clots in the brain have gained the most coverage, patients with clots in other large veins and arteries have also been diagnosed.
These blood clots in the brain, known as cerebral venous sinus thromboses or CVST, are dangerous enough on their own, but they may be developing elsewhere as well.
If people develop blood clots after being newly vaccinated against coronavirus, doctors are recommended to run tests and not to use heparin to treat the clots until VITT has been ruled out.
According to new guidelines published earlier this week by the American Society of Hematology, the disorder is very similar to a known condition known as heparin-induced thrombocytopenia. The disorder is often referred to as VITT. Standard post-vaccination malaise, headache, and fever, according to the ASH, are not cause for concern.
