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AstraZeneca Covid Vaccine Linked To Another Fatal Blood Clotting Disorder

The AstraZeneca's Covid-19 vaccine was named CoviShield in India.

New Delhi:

British-Swedish pharma giant AstraZeneca's Covid-19 vaccine, made in collaboration with Oxford University has been found to raise the risk of vaccine-induced immune thrombocytopenia and thrombosis (VITT) -- a rare but fatal blood clotting disorder, claimed researchers today.

While not new, VITT emerged as a new disease following adenovirus vector-based Oxford-AstraZeneca vaccine -- sold as Covishield in India and Vaxzevria in Europe -- at the height of the Covid pandemic in 2021.

"An unusually dangerous blood autoantibody directed against a protein termed platelet factor 4 (or PF4)" was found as the reason for VITT.

In separate research in 2023, scientists from Canada, North America, Germany and Italy described a virtually identical disorder with the same PF4 antibody that was fatal in some cases after natural adenovirus (common cold) infection.

Now in a new research, Flinders University in Australia and other international experts found that the PF4 antibodies in both adenovirus infection-associated VITT and classic adenoviral vector VITT share identical molecular fingerprints or signatures.

"Indeed, the pathways of lethal antibody production in these disorders must be virtually identical and have similar genetic risk factors," said Professor Tom Gordon from Flinders

The researcher noted that the "findings have the important clinical implication that lessons learned from VITT are applicable to rare cases of blood clotting after adenovirus (a common cold) infections, as well as having implications for vaccine development".

The same team had in a 2022 study "cracked the molecular code of the PF4 antibody and identified a genetic risk factor".

Their new findings, published in the New England Journal of Medicine, also have important implications for improving vaccine safety.

The research comes after AstraZeneca "accepted, in a legal document submitted to the High Court in February, that its Covid vaccine 'can, in very rare cases, cause Thrombotic Thrombocytopenic Syndrome (TTS)'."

TTS is a rare side effect that can cause people to have blood clots and a low blood platelet count. It has been linked to the death of at least 81 people in the UK as well as hundreds of serious injuries.

The company has also voluntarily withdrawn "marketing authorisation" of its Covid vaccine from Europe and other global markets.  (Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)

Genetics Played Role In Rare Blood Clots Linked To COVID-19 Vaccines, Researchers Find

Rare but deadly blood clots tied to Johnson & Johnson and AstraZeneca Plc's Covid-19 shots were caused by an autoimmune reaction that some people are predisposed to, researchers found, a discovery that they say will shape development of future vaccines.

Adenovirus-based vaccines, like the J&J and AstraZeneca shots that were later pulled from the market, contain a component that, in genetically susceptible people, can trigger the production of unusually structured antibodies against a protein involved in blood clotting, scientists said Wednesday in a letter to the New England Journal of Medicine. Researchers plan to identify the culprit and then try to remove it using genetic engineering.

Read More: How COVID-19 Vaccines and Infections Are Tweaking Our Immunity

An extremely similar deleterious antibody response occurs in susceptible patients after infection with adenoviruses, which often infect the airways and lead to cold-like symptoms, the study found. It's not known how many people may be susceptible to the complication, said Tom Gordon, head of immunology at Flinders University in South Australia, whose molecular sleuthing led to the finding.

The immune reaction linked to the shot is "a new disease," he said in an interview. Hematologists and intensive care specialists are likely to spot more cases as they become familiar with it, he said.

"It's a kind of autoimmunity where we know the trigger," said immunologist James McCluskey, assistant vice chancellor of the University of Melbourne, who wasn't involved in the research. "That's unusual. In most cases we never get a handle on the trigger."

Out of more than 18 million people who received the single-dose J&J vaccine, 60 cases of the clotting disorder were reported and nine people died, according to the Yale School of Medicine. 

A small number of clot-related deaths tied to the AstraZeneca vaccine led to its withdrawal or restriction in Denmark, Norway and other countries in 2021. The complication occurred in about 2-3 people per 100,000 vaccinated with the Astra shot under age 60 in Australia, where it hasn't been available since March 2023. The European Commission withdrew the marketing authorization for the immunization in March 2024.

"AstraZeneca welcomes any further examination of the possible underlying mechanism of thrombosis with thrombocytopenia syndrome (TTS), given that, despite extensive investigation, we do not yet understand the mechanism that can in very rare cases be a trigger for TTS," a spokesperson for the company said.

J&J also said it supports research that helps guide development of safe and effective vaccines. 

Read More: The Miracle Workers: Vaccine Scientists Are TIME's 2021 Heroes of the Year

"More data are needed to fully understand potential factors that may be associated with this rare event, including its potential relationship with adeno- and other viruses, to draw appropriate conclusions about the underlying pathogenesis," the company said in an email. 

Both shots played an important role in vaccine programs during the early stages of the pandemic. One analysis found the Astra vaccine saved an estimated 6.3 million lives in 2021.

The mRNA vaccines made by the Pfizer Inc.-BioNTech SE partnership and Moderna Inc. Were later found to be more effective at protecting against Covid and have been updated to tackle more recent virus variants.

AstraZeneca's Covid-19 Vaccine Can Cause A Second 'Rare' Blood Clotting Disorder?What Research Says

Within a little over a week since the UK-based pharmaceutical giant AstraZeneca announced a global roll back of its Covid-19 vaccine citing commercial reasons amid a row over the vaccine causing Thrombosis Thrombocytopenia Syndrome (TTS), fresh research has identified its potential to cause another rare blood clotting disorder called Vaccine-Induced Immune Thrombocytopenia and Thrombosis (VITT).

Recently, Astrazeneca's vaccine, globally known as Vaxzevria, or Covishield in India, came under scrutiny as the pharma company admitted in court documents that in 'very rare cases' Covishield could cause a blood clot-related disorder called Thrombosis Thrombocytopenia Syndrome (TTS) .

What is VITT?

According to the scientists from Australia's Flinders University, VITT emerged in 2021 during the Covid-19 pandemic following widespread usage of the Oxford-AstraZeneca vaccine, which is based on adenovirus vectors. The blood clotting related disorder, as per research, occurs within 4 to 42 days of taking the Covid vaccine.

VITT: Symptoms, cause of concern

According to the American Society of Hematology, the symptoms could include the following:

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