"These events appear to be extremely rare," the agencies said in a joint statement. The reports appear similar to a rare, unusual type of clotting disorder that European authorities say is possibly linked to another COVID-19 vaccine not yet cleared in the U.S., from AstraZeneca. Dr. Peter Marks, Director, FDA Center for Biologics Evaluation and Research, explains why the FDA recommended a pause in the administration of the Johnson & Johnson vaccine despite the appearance of blood clots being so rare. San Diego County was only expected to receive about 3,400 J&J doses for the entire week, so the pause is not likely to make a large impact on distribution efforts.