FDA, CDC Recommend Pause for Johnson & Johnson COVID-19 Vaccine Over Rare Blood Clots

By Kelly Young

Edited by David G. Fairchild, MD, MPH, and Lorenzo Di Francesco, MD, FACP, FHM

The FDA and CDC have asked that clinicians temporarily stop administering the Johnson & Johnson COVID-19 vaccine after the occurrence of rare but severe venous thrombotic events. Officials expect the pause to last "a matter of days."

Out of 6.8 million people who've received the vaccine in the U.S., six women have developed cerebral venous sinus thrombosis (CVST) with thrombocytopenia. One patient died and another is in critical condition. Among people with normal levels of platelets, the expected rate of CVST is about 2 to 14 cases per million people per year.

"The real thing that's so notable here is not just the cerebral venous sinus thrombosis or the thrombocytopenia," said Dr. Peter Marks, director of the FDA's Center for Biologics Evaluation and Research, at a press briefing on Tuesday. "Those two things can occur. It's those two things together that makes a pattern."

Similar adverse events have occurred in Europe among people vaccinated with AstraZeneca's COVID-19 vaccine. Both vaccines are adenovirus-vectored. Cases have not been reported with the Pfizer-BioNTech and Moderna vaccines, which are mRNA-based.

For the Johnson & Johnson vaccine, patients were between ages 18 and 48 years and developed symptoms 6 to 13 days after receiving the vaccine.

Dr. Marks advised that for patients presenting with severe headache, abdominal or leg pain, or shortness of breath, clinicians should inquire about their vaccine history and consider CVST if platelet levels are low. Suspected cases should not receive heparin.

The CDC's Advisory Committee on Immunization Practices will hold an emergency session to discuss the findings on Wednesday.

The White House said that the pause shouldn't affect its COVID-19 vaccination goals, as the Johnson & Johnson vaccine makes up less than 5% of all doses administered in the U.S.