A rare but serious clotting disorder linked to certain COVID-19 vaccines and natural adenovirus infections has puzzled scientists for years.
An international team of researchers from McMaster University (Canada), Flinders University (Australia), and Universitätsmedizin Greifswald (Germany) has identified why a very small number of people developed serious blood clots after receiving certain COVID-19 vaccines or after a natural adenovirus infection. Their findings point to an unexpected mistake by the immune system, which in rare cases targets the wrong molecule.
The study, published in the New England Journal of Medicine, explains how the body can sometimes produce harmful antibodies that attack its own blood proteins, leading to vaccine-induced immune thrombocytopenia and thrombosis (VITT). The researchers pinpointed the exact viral component capable of triggering this response under unusual conditions.
They also described a previously unknown biological pathway showing how a normal immune defense can shift into a harmful reaction. This insight may help scientists better understand other rare, antibody-driven side effects linked to infections, medications, or environmental exposures.
“This study shows, with molecular precision, how a normal immune response to an adenovirus can very rarely go off‑track. By identifying the exact viral protein involved and the specific antibody change that drives this misdirection, we now understand not only what happens in VITT but why,” says Theodore Warkentin, corresponding author of the study and professor emeritus in the Department of Pathology & Molecular Medicine at McMaster University.
“What’s exciting is that we can now point to a specific viral component that can be redesigned. It means future adenoviral vaccines can keep all their advantages while sidestepping the rare immune misfire that causes VITT,” he adds.
