Scientists have discovered how adenovirus-based vaccines cause fatal blood clots and bleeding in a very small number of people. Provided by Getty Image Bank
The principle behind how adenovirus-based vaccines cause fatal blood clots and bleeding in a very small number of people has been identified. This is the type used in some new coronavirus infectious disease (COVID-19) vaccines, such as AstraZeneca.
A research team from the Department of Pathology and Molecular Medicine at McMaster University in Canada identified the mechanism of development of ‘vaccine-induced immune thrombocytopenia and thrombosis (VITT)’, a rare side effect that occurs after receiving an adenovirus-based COVID-19 vaccine, and published the research results in the international academic journal ‘New England Journal of Medicine’ on the 11th (local time).
VITT has been reported to occur in patients receiving blood thinners. In 2021, the same symptoms appeared in people who received the AstraZeneca COVID-19 vaccine in Europe, and additional cases also occurred among people who received a similar COVID-19 vaccine from the American company Johnson & Johnson.
It is estimated that it occurs in approximately 1 in 200,000 people who receive the vaccine. What they have in common is that adenovirus was used as a delivery vehicle for messenger ribonucleic acid (mRNA), the core of the vaccine.
The cause is that the protein that makes up the adenovirus reacts with a specific mutation in B cells and produces antibodies that bind well to the PF4 protein, which is involved in blood coagulation. B cells are immune cells that produce antibodies, which are proteins designed to attack specific targets.
The research team used mass spectrometry to precisely analyze the amino acid sequence of PF4-binding antibodies extracted from 21 VITT patients. A common type of amino acid, glutamic acid or aspartic acid, was present at a specific location in the PF4-binding antibodies of VITT patients. It is an amino acid with a negative charge.
The mutant antibody, which has a strong negative charge, easily combined with the PF4 protein, which has a strong positive charge, and activated platelets, which are the key to blood coagulation.
Platelet activation releases more PF4, starting a chain reaction that causes blood to clump together. It consumes platelets in the body and causes unstoppable bleeding, leading to fatal results.
The research team demonstrated that PF4-binding antibodies from two patients could be reproduced in the laboratory and cause VITT-like symptoms in mice. To verify that the amino acid change was the cause, a version using another amino acid, lysine, was created instead of glutamic acid, and the formation of blood clots was reduced.
The research team also confirmed through experiments that patients with VITT had previously been infected with adenovirus and that their B cells were prepared to recognize ‘pVII’, a type of adenovirus protein.
According to the European Medicines Agency (EMA), about 900 cases of VITT have been reported in Europe after vaccination with the AstraZeneca or Johnson & Johnson vaccine. Of these, 200 cases resulted in death. It is estimated that approximately 3 billion doses of the AstraZeneca vaccine have been administered worldwide, saving millions of lives.
Adenovirus vaccines are inexpensive to manufacture and do not require cryogenic storage, making them easy to distribute. It is used to develop vaccines for other infectious diseases such as the deadly Ebola virus, malaria, and Nipah virus. It is analyzed that new adenovirus vaccines may also cause VITT.
Based on the results of this study, scientists expect that they will be able to prevent the occurrence of VITT in new adenoviruses and increase their safety.
– doi.org/10.1056/NEJMoa2514824
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date: 2026-02-12 09:33:00