Rare blood clots from Johnson & Johnson, Astra Covid-19 shots linked to genetics
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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.
PHOTO: AFP
WASHINGTON – Rare but deadly blood clots tied to Johnson & Johnson (J&J) and AstraZeneca Covid-19 shots were caused by an autoimmune reaction that some people are predisposed to, a discovery that researchers 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 can trigger blood clots in people who are genetically susceptible, scientists said on May 15 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.
It is not known how many people may be susceptible to the complication, said Professor 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. “I think as haematologists and intensive-care specialists become more familiar with these conditions, more cases will be described.”
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 two to three people per 100,000 vaccinated with the Astra shot under age 60 in Australia, where it has not been available since March 2023.
The European Commission withdrew the marketing authorisation for the immunisation 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.
“More data is 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 e-mail.
Both shots played an important role in vaccine programmes 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-BioNTech partnership and Moderna were later found to be more effective in protecting against Covid-19 and have been updated to tackle more recent virus variants. BLOOMBERG
