The cause of thrombosis linked to the AstraZeneca and Johnson & Johnson vaccine finally identified?

Vaccine-induced thrombotic thrombocytopenia, or VITT, is a side effects of AstraZeneca and Johnson & Johnson formulas which both use a modified adenovirus. An extremely rare event, scientists still wonder about the mechanisms that lead to the formation of clots blood after the first injection of these vaccines.

The embrace between PF4 and adenovirus

A research team from the University of Arizona may have deciphered part of this mechanism. By analyzing the structure of the adenovirus contained in the vaccine ofAstraZeneca at a very fine level of detail, on the order of an angstrom. The adenovirus capsid, which serves as a vehicle for genetic material of SARS-CoV-2, can physically bind to platelet factor 4 (PF4), a protein blood in the characteristic clots of VITT.

More specifically, PF4 can bind to negatively charged areas on the surface of the adenovirus, called hexons. Since PF4 is positively charged, the vector acts as a magnet. This interaction is considered abnormal by the immune system. From antibody bind to it in order to neutralize it, causing a cascade of reactions that ends in the formation of a clot and thrombosis.

Modifying adenovirus in vaccines

” With a better understanding of the mechanism by which PF4 and adenoviruses interact, there is an opportunity to improve the vaccine shell, the capsid, to prevent interaction with PF4. Modifying ChAdOx1 to reduce the negative charge may reduce the chances of causing thrombotic thrombocytopenia », Explains Alexander Baker, first author of the study.

Indeed, in this mechanistic approach, it is the interaction with certain highly electronegative areas of the adenovirus which would be one of the causes of VITT. By modifying the amino acids to which PF4 attaches, the risk of a blood clot forming in fine is reduced.

AstraZeneca vaccine: thrombosis considered a rare side effect

Article published on April 8, 2021 by Julie Kern

After analyzing several cases of thrombosis after the injection of the Vaxzeria vaccine, the European Medicines Agency considers that these symptoms serious are a rare consequence of vaccination with the formula developed by AstraZeneca.

A day after the statement by Marco Cavaleri, head of vaccine strategy at the European Medicines Agency (EMA), the health institution’s safety committee published his official conclusions. According to them, blood clots, accompanied by platelet deficiency, should be considered a rare side effect of AstraZeneca vaccine, Vaxzeria. This decision is based on the study of 62 cases of cerebral venous sinus thrombosis and 24 cases of splanchnic venous thrombosis (blood circulation of theabdomen), 18 of which have been shown to be fatal, reported as of March 21. Since then, the number of cases has increased: 169 cases of cerebral thrombosis and 53 cases of abdominal thrombosis were reported to EudraVigilance, which compiles the side effects for drugs authorized in Europe. As of April 4, 2021, 34 million people have been vaccinated with Vaxveria in the 27 countries of the European Union.

For the moment, there is no known risk factor for thrombosis, however women under the age of 60 are the most affected by the phenomenon. Thus, the EMA recommends that healthcare professionals and vaccinees be aware that this risk, although very low, exists within two weeks of the injection. If shortness of breath, pains chest and abdominal swelling, swelling of the legs, neurological symptoms such as headache Persistent or blurred vision and small red dots around the injection site, see a doctor. The EMA reaffirms that the benefit-risk balance of the Vaxzeria vaccine is still in favor of the benefits.

AstraZeneca: clear link between vaccine and thrombosis, according to EMA official

Article published on April 6, 2021 by Julie Kern

In an interview, a vaccine strategy manager at the European Medicines Agency believes that there is a clear link between the AstraZeneca vaccine and cases of thrombosis. No official communication in this direction has yet been made.

Since its temporary suspension, the vaccine AstraZeneca anti-Covid (Vaxzeria) is shunned by those eligible for vaccination, in particular because of side effects caused by the latter. What particularly worries the population is the appearance of thrombosis of the cerebral venous sinuses, that is to say the formation of a clot in the blood vessels which supply the blood. brain. These events mainly concern young women under the age of 50 and are accompanied by a thrombocytopenia, a quantity of platelets lower than normal values.

A link between thrombosis and vaccine established?

In his last communication on the subject, the European Medicines Agency (EMA) indicates that ” a causal link with the vaccine is not proven, but it is possible, and analyzes are continuing “. But, on April 6, 2021, Marco Cavaleri, the person in charge of the vaccine strategy at the EMA, declared in the Italian daily Il Messaggero : “We can now say it, it is clear that there is a link with the vaccine. What causes this reaction, however, we don’t yet know. An official announcement from the EMA, which has not confirmed the statements of Marco Cavaleri, should appear soon, because scientists are meeting around the question between April 6 and 9, 2021.

If, according to Marco Cavaleri, there is a link between the vaccine and thrombosis, the mechanism involved has not yet been deciphered. The association of thrombosis with thrombocytopenia, which leads to bleeding disorders, is quite unique. According to Inserm, it is linked to changes in the immune system and has not yet been observed following vaccination. Despite these suspicions, the overall benefit / risk ratio of the Vaxzeria vaccine is still positive, but it could be re-estimated based on age. In France, the High Authority of Health recommends vaccinating only people over 55 years of age with the Vaxzeria vaccine.