Understanding Mechanisms of Thrombosis and Thrombocytopenia in COVID-19 and with SARS-CoV-2 Vaccines

Project summary:

The vast majority of people who have a COVID-19 vaccine experience only mild side effects lasting for two or three days. However, in March 2021 reports emerged of a small number of people being admitted to hospital with blood clots in the major veins in the brain or in the abdomen, but at the same time a low level of platelets which are responsible for clotting in the blood.

We aim to:

  • Investigate how common thrombotic thrombocytopenia syndrome (TTS) was: before COVID-19; in those who have been vaccinated against COVID-19 and in those suffering from COVID-19.
  • Understand why a very small number of those vaccinated against COVID-19, and also those with COVID-19 itself, develop blood clotting disorders.
  • Investigate the changes in the body that lead to the unique combination of blood clots and low platelet count seen in TTS.

We have brought together researchers and doctors from across the UK with expertise in many different areas. These include: using information in electronic health records to understand disease; vaccine safety and effectiveness; understanding how the immune system and the genes controlling the immune system respond to viral infection and vaccination; treating people who have blood clots and understanding how and why blood clots form. Our team will work together to understand the biology behind TTS and develop solutions to prevent and treat TTS.

Our research will discover why COVID-19 vaccines can lead to TTS in rare cases. This will be important for redesigning COVID-19 vaccines to avoid TTS and for development of new vaccines in any future pandemics and against existing diseases for which there is no vaccine. The benefit-risk ratio of the COVID-19 vaccines is highly beneficial. Understanding how TTS develops has the potential to further improve the safety of current and future vaccines.


National Institute for Health Research

Leader researcher:

Professor Sir Munir Pirmohamed

Lead institution:

University of Liverpool