The Virginia Department of Health has paused the use of the Johnson & Johnson one-dose COVID-19 vaccine after the Centers for Disease Control and Prevention and the Food and Drug Administration said they are investigating a rare and severe blood clot found in six people who have received the vaccine and recommended that its use be suspended.

In the six cases, all among women ages 18 to 48, symptoms developed six to 13 days after receiving the vaccination. In these cases, according to a joint statement from Dr. Anne Schuchat, principal deputy director of the CDC and Dr. Peter Marks, director of the FDA’s Center for Biologics Evaluation and Research, “a cerebral venous sinus thrombosis blood clot was seen in combination with low levels of blood platelets.”

They said treatment of this specific blood clot is different than normal in that the administration of the anticoagulant drug heparin could be dangerous, and alternative treatments are needed.

Marks said in an April 13 media briefing that of the six people who had the blood clot, one died and another is in critical condition.

In Virginia, state vaccine coordinator Dr. Danny Avula said in a statement that the Virginia Department of Health is closely monitoring the situation.

“In Virginia, we will cease all Johnson & Johnson vaccines until this investigation is complete,” Avula said. “If you have an upcoming appointment for the Johnson & Johnson vaccine, you will be contacted to reschedule that appointment.”

Avula said the pause shows that measures to monitor vaccine safety are working. He said the state would continue the vaccine rollout with the Pfizer BioNTech and Moderna vaccines.

Walgreens and CVS Health also announced that they would pause their use of the Johnson & Johnson vaccine.

Through April 12, more than 6.8 million Johnson & Johnson vaccine doses have been administered in the United States.

In his April 9 media briefing, Avula said there were a couple of vaccine clinics in both North Carolina and Colorado where the clinical officer on site felt there were more side effects from the vaccine than they were used to seeing — there were reports of dizziness, nausea and fainting — so they had halted Johnson & Johnson vaccinations.

In North Carolina, at least 26 people were affected by adverse reactions to the shot, and 11 in Colorado reported having side effects from the vaccine, according to published reports. A Georgia vaccine site had also halted the use of the Johnson & Johnson vaccine after eight people suffered adverse reactions after receiving it, and a CDC spokeswoman said it was aware of some people who had experienced an adverse reaction to the shot in Iowa.

However, Avula said the CDC investigated the North Carolina and Colorado cases and did not have concerns, and asked those clinics to reopen and administer that lot of the Johnson & Johnson vaccine.

Through April 12, Virginia has received 255,600 doses of the Johnson & Johnson vaccine, including 19,600 doses that were shipped the previous day, and 90,300 that were shipped April 4.

Christopher Newport University in Newport News, in a news release, said it had planned to vaccinate people on campus April 13 using only the Johnson & Johnson vaccine provided by Riverside Health System.

However, it said Riverside was replacing the Johnson & Johnson vaccines with Moderna vaccines and everyone with an appointment would be able to keep their appointments. The school also said those getting vaccinated would get “clear instructions” on where to go to get their second dose.

The CDC’s Advisory Committee on Immunization Practices will meet April 14 to further review the cases and determine what potential significance they have. The FDA will review that analysis as it also investigates the cases. Until that process is complete, both Schuchat and Marks recommend putting a pause on the use of the Johnson & Johnson vaccine “out of an abundance of caution.”

They said health care providers need to be aware of the potential for blood clots resulting from the vaccine and the unique treatment this type of blood clot needs.

Anyone who has received the Johnson & Johnson vaccine who develops severe headaches, abdominal pain, leg pain or shortness of breath within three weeks after being vaccinated should contact their doctor. Health care providers should report adverse events to the Vaccine Adverse Event Reporting System.

Schuchat said that anyone who received the Johnson & Johnson vaccine more than a month ago is at very low risk for side effects. She said anyone who has received it in the past two weeks should be aware of those symptoms.