Researchers claim rare but deadly blood clots tied to Johnson & Johnson and AstraZeneca Covid-19 vaccines

Scientists revealed that adenovirus-based vaccines like those from J&J and AstraZeneca, which were withdrawn, contain a component capable of triggering blood clots in individuals with a genetic predisposition.

16 May 2024

By Sukhmani Kooner 

Researchers have discovered that the rare yet severe blood clots associated with the Johnson & Johnson and AstraZeneca Covid-19 vaccines result from an autoimmune response that certain individuals may be prone to. They assert that this finding will influence the development of future vaccines.

Scientists, in a letter to the New England Journal of Medicine on 15th May, revealed that adenovirus-based vaccines like those from J&J and AstraZeneca, which were withdrawn, contain a component capable of triggering blood clots in individuals with a genetic predisposition. They plan to identify and potentially eliminate this component through genetic modification. 

Tom Gordon, head of immunology at Flinders University, whose research led to this discovery, emphasised the uncertainty surrounding the extent of vulnerability to this complication. He described the immune reaction linked to the vaccine as a novel condition, anticipating more cases to emerge as specialists become more familiar with it.

According to Bloomberg, the Yale School of Medicine reported that out of over 18 million individuals who received the single-dose J&J vaccine, there were 60 instances of the clotting disorder, leading to 9 fatalities.

A few clot-related deaths associated with the AstraZeneca vaccine prompted its withdrawal or restriction in countries like Denmark, Norway and others in 2021. In Australia, where the vaccine has not been available since March 2023, the complication affected approximately 2-3 individuals per 100,000 vaccinated with the AstraZeneca shot under the age of 60. The European Commission revoked the vaccine’s marketing authorisation in March 2024, according to Bloomberg.

“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, as per the report.