U.S. health officials recommended a pause in the use of Johnson & Johnson’s COVID-19 vaccine on concerns about rare and severe blood clotting side effects.
A type of brain blood clot called cerebral venous sinus thrombosis was seen in combination with low levels of blood platelets in six women between the ages of 18 and 48, the U.S. Centers for Disease Control and Prevention and Food and Drug Administration said Tuesday in a joint statement. As of April 12, more than 6.8 million doses of the vaccine have been administered, the agencies said.
The CDC will convene a meeting Wednesday of its Advisory Committee on Immunization Practices to review the cases and assess their potential significance. The FDA will review the CDC assessment as it also investigates these cases, according to the statement.
The recommended pause may further complicate efforts to vaccinate the world, just weeks after a vaccine relying on a similar approach and developed by AstraZeneca Plc and the University of Oxford raised similar concerns in Europe.
It also has the potential to slow the U.S. vaccination campaign, where officials are relying on a pledged 100 million doses of J&J’s vaccine to help cover all adults by the end of May.
“We are recommending a pause in the use of this vaccine out of an abundance of caution,” the CDC and the FDA said in the statement. “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.”
Concerns about blood clots could discourage some people from taking the J&J shot, which has so far proved popular because it’s a single dose.
The move follows cases of similar clots that have followed the use of the AstraZeneca vaccine in Europe, particularly in younger adults. The clotting concern has prompted many countries to impose age restrictions on use of the Astra vaccine, which was co-developed with the University of Oxford.
J&J has also begun shipments to the European Union. The bloc’s drugs regulator, the European Medicines Agency, did not immediately respond to a request for comment.
The EMA has also said that it’s assessing blood clots in people who received the J&J vaccine, after four serious cases of unusual clots accompanied by low blood platelets, one of which was fatal, emerged.
J&J representatives didn’t immediately respond to a request for comment. The shares fell 3% in premarket U.S. trading.