There is a much higher risk of brain blood clots from Covid-19 infection than there is from vaccines against the disease, British researchers said on Thursday, after the rollout of inoculations was disrupted by reports of rare clots.

AstraZeneca and Johnson & Johnson (J&J) have both seen very rare reports of cerebral venous sinus thrombosis (CVST) linked to their vaccines. On Wednesday, the United States paused vaccinations using J&J's shot while a link with clots was investigated, with Denmark ditching AstraZeneca's shot over the issue.

British and European regulators have stressed that...