SAN FRANCISCO (KRON) — The U.S. is recommending that COVID-19 vaccination sites temporarily pause administering the Johnson & Johnson vaccine.

The Centers for Disease Control and Prevention, along with the U.S. Food and Drug Administration said Tuesday that six women reported developing a rare blood clot after getting the J&J dose. The U.S. has already administered about 6.8 million doses.

The six women were between the ages of 18 and 48, and developed the symptoms about 6-13 days after vaccination, the agencies said. One of them has died.

The agencies said as of now, the cases appear to be “extremely rare.”

An advisory board for immunization practices will review the cases Wednesday to determine how significant the severe blood clot concern is.

The blood clot type is called cerebral venous sinus thrombosis (CVST) and was seen in combination with low levels of blood platelets (thrombocytopenia).

“Treatment of this specific type of blood clot is different from the treatment that might typically be administered. Usually, an anticoagulant drug called heparin is used to treat blood clots. In this setting, administration of heparin may be dangerous, and alternative treatments need to be given,” according to the agencies.

The halted vaccines are out of an abundance of caution, the agencies said.

“This is important, in part, to ensure that the health care provider community is aware of the potential for these adverse events and can plan for proper recognition and management due to the unique treatment required with this type of blood clot.”

CDC and FDA on April 13, 2021

People who have received the J&J vaccine who develop severe headache, abdominal pain, leg pain, or shortness of breath within three weeks after vaccination should contact their health care provider. Health care providers are asked to report adverse events to the Vaccine Adverse Event Reporting System at

There will be a press conference expected at 7 a.m. PST regarding the news.