The exact cause of this adverse reaction is still being investigated, but it appears that the adenovirus contained in the vaccine may accidentally bind to a small protein called platelet factor 4 (PF4), triggering an immune response that leads to the formation of blood clots. However, it’s important to note that the risk of TTS is much lower than the risk of clots from COVID-19 infection itself.
A 2021 study found that the number of TTS cases caused by the AstraZeneca vaccine was significantly lower than the number of blood clots resulting from COVID-19 infection. Furthermore, the study found that the risk of TTS was lower after the second dose of the vaccine than after the first, and serious side effects occurred relatively soon after administration. Despite these risks, experts agree that the benefits of vaccination far outweigh its risks.
