I had wondered about this as well - in the pool of people who have gotten the J&J vaccine, how many would we expect to have developed a blood clot under normal circumstances anyway?
That's exactly what they'll be studying to see if it's statistically relevant. They're being super cautious. Some would say over cautious but I think it's fine since J&J is currently only 5-10% of the vaccine supply going out. Which means a slight slow down in vaccine supply but not as big a deal as AZ in Europe since that is their main supply.
