(DEVELOPING STORY) – The Food and Drug Administration together with the Centers for Disease Control and Prevention (CDC) is recommending a pause in the rollout of the Johnson & Johnson COVID-19 vaccine after several instances of a severe blood clot in recipients.

According to the FDA, there have been six reported cases of the rare and severe type of blood clot in over 6.8 million Johnson & Johnson COVID-19 vaccine recipients.

“Right now, these adverse events appear to be extremely rare,” the agency said on Twitter. “Treatment of this specific type of blood clot is different from the treatment that might typically be administered. CDC will convene a meeting of the Advisory Committee on Immunization Practices (ACIP) tomorrow to further review these cases and assess their potential significance. FDA will review that analysis as it also investigates these cases.”

However, until that review is completed, the FDA is “recommending this pause.”

“This is important to ensure that the health care provider community is aware of the potential for these adverse events and can plan due to the unique treatment required with this type of blood clot,” the FDA said on Twitter.

The company had told the White House it would deliver 100 million doses by the end of May, but faced a recent production blunder at a Baltimore plant and saw several vaccination sites shut down early over the last week because of potential adverse reactions.

In Georgia, eight people experienced lightheadedness, but officials could not rule out whether heat was a factor. In North Carolina, four people were taken to the hospital for reactions “consistent with known common side effects.” In Iowa, three people experienced extreme lightheadedness, and in Colorado 11 people experienced dizziness and nausea.

This is a developing story and more information will be released at a later time.