New treatment demonstrated for people with vaccine clots

Angela Huynh, PhD works at the McMaster Platelet Immunology Laboratory. Photo credit: McMaster University

McMaster University scientists have demonstrated a new life-saving treatment for people with vaccine-induced blood clots.

Researchers at the McMaster Platelet Immunology Laboratory (MPIL) recommend two treatments, a combination of anticoagulant drugs with high doses of intravenous immunoglobulin, to combat vaccine-induced immunothrombotic thrombocytopenia (VITT).

The effectiveness of the treatment was described in a report on three Canadian patients who received the AstraZeneca vaccine and subsequently developed VITT. Two had blood clots in their legs and the third had blood clots that blocked arteries and veins in their brain.

“If you were a patient with VITT, I would tell you that we know one approach to treatment. We can accurately diagnose it with our tests, treat it, and we know exactly how the treatment works,” said Ishac Nazy, scientific director of the laboratory and associate professor of medicine.

“Our job is to understand this disease mechanism in order to improve diagnosis and patient management. This study combines successful laboratory diagnostics and patient care. It’s a real translational medicine approach that is really our strength, right at the bedside. “

VITT occurs when antibodies attack a blood protein called platelet factor 4 (PF4), which activates platelets in the blood, causing them to clump and form clots. Blood samples taken from the patients after treatment showed reduced antibody-mediated platelet activation in all cases.

While the study patients were older, many VITT cases involved younger people. However, Nazy and his MPIL colleagues said VITT was a rare disease regardless of people’s age.

The laboratory’s scientists include medical professors Donald Arnold and John Kelton, and professor of pathology and molecular medicine Ted Warkentin. Together, they developed an effective VITT test and treatment, building on their previous research on heparin-induced thrombocytopenia (HIT).

Although the two conditions are similar, using a standard HIT antibody test to detect VITT can produce false negative results.

This prompted the scientists to modify the HIT test to detect VITT-specific antibodies found, albeit rarely, in patients with a COVID-19 vaccine.

Subsequent laboratory tests on blood samples from patients showed how high doses of immunoglobulin combined with blood-thinning drugs stopped platelet activation and clot formation.

“We now understand the mechanism that activates and clots platelets,” said Nazy.

The study was published today in the New England Journal of Medicine.

COVID-19 Vaccination: Thrombosis Can Be Prevented With Immediate Treatment Provided by McMaster University

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