By Tim Mastro

WILMINGTON — Delaware is pausing its administration of the single-dose Johnson & Johnson COVID-19 vaccine as the Centers for Disease Control and Prevention and the Food and Drug Administration investigate reports of potentially dangerous blood clots.

In a joint statement Tuesday, the CDC and the FDA said they were investigating unusual clots in six women that occurred 6-to-13 days after vaccination. The clots occurred in veins that drain blood from the brain and occurred together with low platelets. All six cases were in women between the ages of 18 and 48.

More than 6.8 million doses of the J&J vaccine have been administered in the U.S. The Delaware Division of Public Health is reporting 21,727 total persons who have been vaccinated with the one-dose vaccine series as of Monday at 11:59 p.m.

“It’s really important that, first of all, the FDA and CDC have a better understanding about these six cases,” said DPH director Dr. Karyl Rattay. “But also so the medical community is aware of how to identify these cases and how to treat it.”

Delaware was already adjusting its J&J appointments due to an expected shortage of the vaccine after a recent batch failed quality standards. However Dr. Rattay said Delawareans might notice some cancellations if they are scheduled for a vaccine, especially at pharmacies who get J&J vaccines shipped directly to them.

Delaware has received a total of 47,400 doses of the J&J vaccine — 31,800 sent to the state for distribution and an additional 15,600 allocated via the Federal Pharmacy Program. It was the latest vaccine approved for emergency use as Delaware has received significantly more doses of the two-dose vaccines Pfizer (362,895) and Moderna (295,000).

The CDC’s Advisory Committee on Immunization Practices will meet Wednesday to discuss the cases and the FDA has also launched an investigation into the cause of the clots and low platelet counts.

“Until that process is complete, we are recommending a pause in the use of this vaccine out of an abundance of caution,” Dr. Anne Schuchat, principal deputy director of the CDC, and Dr. Peter Marks, director of the FDA’s Center for Biologics Evaluation and Research, said in a joint statement.

They are recommending that people who were given the J&J vaccine who are experiencing severe headache, abdominal pain, leg pain, or shortness of breath within three weeks after receiving the shot contact their health care provider.

This story will be updated. The Associated Press contributed to this report.