Canadian doctors said that the treatment of blood clots after the vaccine showed promise, but there was no “slam dunk”.


Since health officials announced the first rare case of post-vaccination thrombosis in Canada in April, scientists have been racing to understand what caused this potentially deadly disease and how to treat it.

Now, a team from Hamilton McMaster University has published new research-supported recommendations, calling on clinicians to combine two treatments: anticoagulant drugs and high-dose intravenous antibody therapy.

The potential effectiveness is outlined in three case studies. The subjects of these case studies are some of the first Canadian patients who developed blood clots after vaccination. This is Published on Wednesday in the New England Journal of Medicine.

The paper stated that all three patients between the ages of 63 and 72 were vaccinated with the AstraZeneca-Oxford COVID-19 vaccine and were later diagnosed with vaccine-induced immune thrombotic thrombocytopenia (VITT) .

Both had blood clotting in their legs, one of them needed to be amputated later, and the internal cerebral arteries and veins of the third were blocked.

Watch | Researchers explain IVIG treatment:

Ishac Nazy is one of the researchers in a new paper focusing on the treatment of blood clots after vaccines, and is the scientific director of the McMaster Platelet Immunology Laboratory. Here, he explains how intravenous immunoglobulin (IVIG) can treat patients with these rare but potentially fatal blood clots. 0:43

“We realized early on that all three patients received anticoagulant therapy [or anti-clotting medication] And intravenous immunoglobulin or IVIG,” said Ishac Nazy, one of the researchers behind the new report and the study’s scientific director. McMaster Platelet Immunology Laboratory.

IVIG is a treatment consisting of antibodies that can be injected intravenously and has long been used to help treat autoimmune diseases.

The paper pointed out that all three patients who received treatment survived.

How does IVIG work?

So, how does IVIG seem—and why—to be effective in patients who experience blood clots after vaccination?

Although more research is needed to understand why this happens in the first place, the research team suspects that, for some people, vaccination with a viral vector vaccine like AstraZeneca will result in the production of antibodies that attack specific blood proteins. Activate the platelets in the blood and cause them to clump together.

Nazy explained that IVIG treatment seems to work by injecting different antibodies into the system that “exceed” the patient’s own supply to prevent a series of events that cause blood clots.

The McMaster Platelet Immunology Laboratory has conducted more than 30 years of research on immune-mediated platelet diseases and operated under the guidance of Dr. Ishac Nazy (left), Dr. Donald Arnold (middle) and Dr. John Kelton (right). (Submitted by McMaster University)

The team believes that the therapy will slow the blood clotting process, so that anticoagulant drugs have time to take effect.

“This is a multifaceted approach, trying to target the coagulation event from different angles,” Nazi said.

The team’s laboratory work found that blood samples from all three patients showed decreased platelet activation after treatment.

Not the “perfect medicine”

However, external experts who have seen the blood clotting conditions of the pre-copy of this paper emphasize that this is just a starting point.

Dr. Sudeep Shivakumar, head of the interim department of hematology at Dalhousie University School of Medicine and service director in Halifax, said that although these three case studies are “encouraging,” they are only needed for more The field of research provides anecdotal evidence.

“This is not a slam dunk,” he added, “but it does provide us with ideas for future research.”

To date, after more than 2.8 million doses of the AstraZeneca-Oxford vaccine have been distributed nationwide, Canada has reported at least 5 deaths and 28 vaccine-induced immune thrombotic thrombocytopenia (VITT) cases. (Jeff Mackintosh/Canada Press)

Dr. Lana Castellucci is a thrombosis doctor and researcher at the Ottawa Hospital Research Institute. She agrees that these findings are just a starting point, but said that these recommendations are consistent with the discussions that clinicians across Canada are discussing how to treat VITT.

For example, Ontario’s COVID-19 scientific advisory form recommends the use of anticoagulant drugs and IVIG at the same time VITT treatment plan list, Which is part of the organization’s interim guidance for healthcare professionals in May.

“The possibility of seeing it as a continuous diagnosis still exists, and knowing that we have effective treatment strategies will definitely help,” Castellucci said.

Nazy himself admits that IVIG is not a “perfect drug” and is not effective for every patient-and pointed out that one of his three patients later required a different treatment, although he eventually improved.

Some people worry Access and supply levels In recent years, plasma-based treatments.

National monitoring plan established

The McMaster Laboratories team set up a national monitoring program for VITT earlier this year, and doctors across the country began to share their clinical data, patient samples, treatment plans, and progress updates.

This helps researchers confirm VITT cases before Canadian doctors encounter this condition, and enables them to evaluate different treatments.

A few months later, there are still major unresolved questions about the mechanism behind VITT and why it attacks certain people in rare cases.

To date, after more than 2.8 million doses of AstraZeneca have been distributed nationwide, Canada has reported at least 28 cases and 5 deaths.

“Are there certain groups at greater risk than others?” Castellucci asked. “Is there an age group at risk? A gender that is more at risk-for example, more women than men?”

She added that the guidelines that allow Canadians to choose to switch between manufacturers for each injection, and that some provinces stop using AstraZeneca for the first injection, “eliminate a lot of the uncertainty that many Canadians face.” .

“We know that mRNA vaccines have not had such complications,” Castellucci said.



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