Oxford University researchers compared incidence of a rare clotting condition—known as CVT, or cerebral venous thrombosis—among people suffering from COVID-19 and other groups. The disease itself places people at far greater clotting-related risks than do any of the three vaccines studied.
Data continues to accumulate as more vaccines are given.
Six cases of another type of CVT clotting, cerebral venous sinus thrombosis, were reported among 6.8 million U.S. recipients of the Johnson & Johnson vaccine. U.S. authorities have paused administration of that vaccine pending further reviews.