Can the vaccine pfizer covid cause thrombosis because i am born with one nternal carotid artery and i have collateral perfusion (willis circle) in the brain? 40 years old?

The incidence of blood clots is very rare, and these involve veins, not arteries. Highly recommend vaccine, especially if florid numbers of cases are occurring. You do not describe any reason to avoid the jab.

An embolism in a single carotid artery could be deadly. Make sure you get a cardiologist to verify you do not have a patent foramen ovale or ventricular septal defect. Make sure you do not have cardiac valve disease or aortic arch disease. Watch out for high blood pressure, high cholesterol or diabetes mellitus, which increase your risks. Thromboses typically occur in the venous circulation only.