Scientists have identified the cause of very rare blood clots in some individuals after adenoviral Covid‑19 vaccines, according to the scientific journal "ScienceDirect." These cases, known as VITT (vaccine-induced immune thrombotic thrombocytopenia), occur when the immune system produces antibodies that mistakenly attack a blood protein called PF4, leading to clotting. The condition is extremely rare and is linked to a combination of genetic background and a minor antibody mutation. Symptoms to be aware of include severe headaches, abdominal pain, leg swelling, difficulty breathing, and red spots on the skin, typically 7–30 days after vaccination. Experts emphasize that the risk is very low, while the benefits of Covid‑19 vaccination remain far greater. Understanding this mechanism could aid in faster diagnosis and treatment, as well as in the development of safer vaccines in the future.