KANSAS CITY, Mo. (AP) — A mass vaccination clinic that was planned at the stadium where the Kansas City Chiefs play has been canceled due to the suspension of the use of the single-dose Johnson & Johnson vaccine.

The problem was that Arrowhead Stadium and the National Guard were not available to administer a second dose if they were to use the Pfizer or Moderna vaccine, according to the Jackson County Health Department.

KSHB-TV reports that the clinic, which was supposed to be the second at Arrowhead, had been planned for April 29-30.

Use of the J&J vaccine was put on hold last week after the Centers for Disease Control and Prevention and the Food and Drug Administration said they were investigating reports of rare but potentially dangerous blood clots.