SARS-CoV-2 vaccination and risk of venous thromboembolism and arterial thrombotic events
Project description
There have been a number of reports of vascular complications after coronavirus vaccination. The complication that is of most concern is a very rare condition of clotting of the veins in unusual places like the brain and the gut which has been associated with low levels of platelets.
We will study all adults alive in England at thebeginning of the pandemic in 2020 with data included in the NHS Digital trusted research environment. We will find out which people had a disease involving blood clots in the arteries (like stroke or heart attack) or in the veins (like deep vein thrombosis, pulmonary embolism or clots in the veins of the brain or gut). We will also find out which of these people were diagnosed with low levels of platelets at the time of their blood clotting event.
We will compare the risk of developing one of these conditions among people who have had a Covid-19 vaccine versus those who have not had a vaccine. We will use statistical methods to account for differences between vaccinated and unvaccinated people (such as age, sex, ethnic group and previous medical history) that might affect the risk of these conditions. We will assess the risks for clotting events of different types, for different vaccines, for people who have had one or two vaccine doses, and for people with different characteristics. Our results will allowus to estimate whether Covid-19 vaccine is associated with an increased risk of one or more of these different types of clotting events, and if so by how much.
This research is needed to provide reliable information to medicines regulators, the Department of Health and Social Care, health professionals and the public about any risks associated with Covid-19 vaccines. Because the clotting events that might be affected are very rare, any increase in risk is likely to be very small. It will, therefore, be important to understand not only whether or not there is an increased risk but also the size of any increased risk and whether it only applies to particular groups of people. It will also be important to understand how any risk compares with the protective benefits of the vaccine, which are known to be substantial.
Project approval
This project has been approved by the CVD-COVID-UK Approvals & Oversight Board (Project ID: CCU002_02).