Thrombosis after vaccination: cause decoded - practical cure

How a Bad Immune Response Can Cause Thrombosis

Following certain vaccinations with adenovirus vaccines, the risk of developing thrombosis is minimal. According to the German Heart Foundation, such complications occur in one to two people in every 100,000 vaccinated. A German research team is currently studying how thrombosis can develop after vaccinations.

A working group of the Medical Clinic and Polyclinic I: Cardiology of the LMU Clinic Munich led by Dr. Leo Nicolai is investigating how thrombosis can occur in rare cases after vaccination with adenovirus vaccines. The team is now reporting on the results obtained so far in the specialist journal "Blood".

Thrombosis in COVID-19 vaccinations

During COVID-19 vaccinations with AstraZeneca's Vaxzevria vaccine and Johnson & Johnson's vaccine, vaccine complications in the form of post-vaccination thrombosis have occurred in very rare cases, often affecting the cerebral veins. For this and other reasons, these vaccines have not been used in Germany since December 2021.

"For the development of future vaccines and the safety of people prone to thrombosis, including patients with cardiovascular disease, it is important to understand the causes and mechanisms of these rare thrombosis as a misguided immune response - here in the part of a vaccination", explains Prof. Dr. Thomas Voiglander. He is Chairman of the Board of the German Heart Foundation.

"It is important to emphasize that when it comes to protection against the consequences of a Covid-19 infection, the advantage is still clearly on the side of the Covid vaccination - even if in rare cases there are sometimes severe side effects. with mRNA- or vector-based Covid vaccines,” emphasizes cardiologist Voigtländer.

What does VIT mean?

Vaccine-induced blood clots in atypical locations such as the cerebral veins are referred to in medical jargon by the abbreviation VITT, which stands for "immuno-thrombotic thrombocytopenia induced by the vaccine". What is meant by this is an erroneous reaction of the immune system.

Platelets (thrombocytes) play a crucial role in this process. Normally, they are used to quickly close wounds to blood vessels to prevent bleeding. Another job of platelets is to react to invaders. These include, for example, pathogens such as viruses and bacteria, but also active ingredients of pharmaceuticals.

Platelets react to vaccine components

As the researchers report, the platelets react to the components of the vaccine. A protein specific to blood platelets called platelet factor 4 (PF4) is activated by the vaccine.

In turn, the immune system responds by forming antibodies against PF4 and subsequently attacking it. This can cause platelets to clump together and form thrombosis.

Decreased platelet count after adenovirus drugs

According to the research group, after vaccination with adenovirus substances, there is a delayed drop in the number of blood platelets (thrombocytopenia). "A misalignment of your own immune system against the body's blood platelets," Nicolai confirms.

The exact mechanisms leading to VITT are currently being studied in detail by the working group led by the enlightened Dr. Nicolaï. “Based on further research into the exact reaction mechanisms, we want to help make vaccinations with adenovirus-based techniques even safer in general in the future,” says Nicolai.

Not only relevant for vaccines

The focus is not just on COVID-19 vaccines from AstraZeneca or Johnson&Johnson. A similar reaction is also known, for example, after administration of the anticoagulant heparin.

The execution of the injection influences the risk of thrombosis

Additionally, the team was able to show in preliminary in-vivo tests for the study that the risk of an immune system overreacting after vaccination with adenovirus-based vaccines is increased if a blood vessel is accidentally touched during the injection. This is not the case with correct application in the muscle.

"We are convinced that this project will lead to a better understanding of the interaction of platelets and the immune system in other cardiovascular diseases and thus make a prospective contribution to basic research and heart health", summarizes Professor Voigtländer. (vb)

Author and source information

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This text corresponds to the requirements of the specialized medical literature, medical guidelines and current studies and has been verified by health professionals.


Graduate editor (FH) Volker Blasek


German Heart Foundation eV/German Heart Research Foundation: From 'Help' to 'Enemy': Blood Platelets Can Cause Thrombosis Due to Improper Immune Response (Published: 06/23/2022), idw-online. by Leo Nicolai, Alexander Leunig, Kami Pekayvaz, et al. : Thrombocytopenia and immune responses directed by splenic platelets after intravenous administration of ChAdOx1 nCov-19; in: Blood (2022),

Important Note:
This article contains general advice only and should not be used for self-diagnosis or treatment. It cannot substitute a visit to the doctor.