ROME—There is a link between AstraZeneca’s COVID-19 vaccine and very rare blood clots in the brain but the possible causes are still unknown, a senior official for the European Medicines Agency (EMA) said in an interview published on Tuesday. “In my opinion, we can now say it, it is clear that there is an association with the vaccine. However, we still do not know what causes this reaction,” Marco Cavaleri, chair of the vaccine evaluation team at the EMA, told Italian daily Il Messaggero when asked about the possible relation between the AstraZeneca shot and cases of brain blood clots. Cavaleri added that the EMA would say there is a link although the regulator would not likely be in a position this week to give an indication regarding the age of individuals to whom the AstraZeneca shot should be given. He did not provide evidence to support his comments. AstraZeneca …