Scientists find clues as to why the AstraZeneca vaccine can lead to clots

The New York Times.

Doctors may have figured out why the vaccine is against it COVID-19 from AstraZeneca can cause some blood clots potentially fatal in very rare cases.

The discovery, made in a pair of reports published Friday in the online edition of the New England Journal of Medicine, could hold the key to the vaccine’s global rollout. AstraZeneca, by helping to develop effective treatments for it secondary effect and give directions to refine the vaccine to fix the problem, experts say.

But it could also hinder efforts to get the vaccine approved in the United States, where it already exists three vaccines available.

READ: Learn how Covid-19 affects mental health

The AstraZeneca vaccine seems to cause certain people to develop antibodies targeting a protein in the body called platelet factor 4 (PF4), which activates and activates platelets Coagulation Cascade, stated report co-author Dr. Theodore Warkentin, a professor of pathology and molecular medicine at McMaster University in Ontario, Canada.

“It is a antibody that the vaccine is somehow activated, and in some circumstances this results in unusual clotting of the lbloodWarkentin remarked.

Also: What to do if symptoms of Covid-19 persist

Side effects

The phenomenon is similar to a rare side effect of a drug caused by heparin, an anticoagulant known as heparin-induced thrombocytopenia, Warkentin noted.

The vaccine’s coagulation side effects are so rare that both the European Medicines Agency (EMA) and the UK Healthcare Products and Medicines Regulatory Agency have decided to keep it on the market, concluding that its benefits outweigh the risks, AstraZeneca said in a statement.

However, the vaccine label will be updated to list blood clotting as an extremely rare possible side effect.

“AstraZeneca has worked very actively with regulatory authorities to implement these changes to product information, and is already working to understand the individual cases, epidemiology and potential mechanisms that could explain these extremely rare events,” the company said.

On April 4, the EMA had received reports of 169 cases of brain clots and 53 cases of abdominal clots among approximately 34 million doses of AstraZeneca administered across Europe, according to Reuters.

In the UK, 19 people have died from blood clots vaccine-related serious injuries, CNN reported.

Cases of clot are similar to what is sometimes reported with the blood thinner heparin


Two of the three COVID-19 vaccines distributed in the United States (Pfizer and Moderna) did not show such side effects. But on Friday, European drug regulators said they were reviewing reports of rare blood clots in four people who received the Johnson & Johnson COVID-19 vaccine. Of the four cases, three occurred in the United States during vaccine deployment and one person died, and the fourth case was reported in a clinical trial, CNBC said.

One of the new AstraZeneca vaccine reports focuses on 11 patients from Germany and Austria who developed severe clotting problems after vaccination, while the other studied the cases of five health professionals aged 32 to 54 who developed the side effect.

The tests showed that all patients had developed PF4 blood clotting complexes similar to those caused by heparin, although none had received the anticoagulant.

These new findings still give doctors no idea who could get sick from excessive clotting after receiving the AstraZeneca vaccine, noted Dr. William Schaffner, a professor of infectious diseases at Vanderbilt University Medical Center in Nashville, Tennessee.

“So far it is aimed at younger age groups, but we cannot determine in advance who those people are. The question will be, as we continue with public policy around the world, how will this vaccine be administered?” Said Schaffner. .

But the findings could help treat people who develop symptoms similar to heparin-induced thrombocytopenia, Warkentin said.

“If someone develops symptoms five or more days after the vaccine, be it headache or neurological symptoms, or abnormal pain or shortness of breath, the person who received the vaccine knows to seek medical attention,” said Warkentin. “Equally important, clinicians who evaluate the patient know how to look for it.”