Toronto: Scientists in Canada have found a new lifesaving treatment for people suffering from rare blood clots associated with COVID-19 vaccination. The researchers at the McMaster University recommend a combination of anti-clotting drugs and high doses of intravenous immunoglobulin to combat vaccine-induced immune thrombotic thrombocytopenia (VITT).
VITT is a rare side effect of adenoviral vector vaccines against COVID-19. It occurs when antibodies attack a blood protein, which results in activation of platelets in the blood, causing them to clump together and form clots. The treatment, described in The New England Journal of Medicine, has proven effective in three Canadian patients who received AstraZeneca vaccine, known as Covishield in India, and subsequently developed VITT.
The patients were between the ages of 63 and 72 years, and one of them was a female. Two suffered clotting in their legs and the third had clots blocking arteries and veins inside their brain. "If you were a patient with VITT, I'd be telling you we know of a treatment approach," said Ishac Nazy, associate professor of medicine at McMaster University.
"We can diagnose it accurately with our tests, treat it and we know exactly how the treatment works," Nazy said. The researchers noted that blood samples taken from the patients after the new treatment showed reduced antibody-mediated platelet activation in all cases.
While the study patients were older, many VITT cases have affected younger people. However, Nazy and his colleagues said VITT is a rare disorder, regardless of people's age.
The scientists devised an effective VITT test and treatment by building on their previous investigations of heparin-induced thrombocytopaenia (HIT), a disorder that results from the direct effect of blood thinner, heparin, on platelet activation. While the two conditions are similar, using a standard HIT antibody test to detect VITT can yield false negative results, the researchers said.
Due to this reason they modified the HIT test to detect VITT-specific antibodies that are found in rare cases in patients who had a COVID-19 vaccine. Subsequent lab tests on patient blood samples showed how high doses of intravenous immunoglobulin coupled with blood-thinner medications shut down platelet activation and stopped clot formation.
IVIG is a blood product prepared from the serum of donors. It is used to treat patients with antibody deficiencies. "We now understand the mechanism that leads to platelet activation and clotting," Nazy added.
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