The Johnson & Johnson (J&J) COVID-19 vaccine will remain on pause after an advisory committee to the Centers for Disease Control and Prevention (CDC) said it needed more data to be able to vote on a recommendation, which may come in a week to 10 days.
Federal health officials halted the use of the J&J vaccine after reports of rare and severe blood clots in the brain with reduced blood platelet levels (thrombocytopenia) occurred after some people were inoculated.
The Advisory Committee on Immunization Practices (ACIP), tasked with developing recommendations on the use of vaccines, held an emergency meeting Wednesday afternoon to discuss the incidence of blood clots with low platelets in seven people following the J&J vaccine. But data was available for only six of the seven individuals.
More than 7.2 million doses of the J&J COVID-19 vaccine have been administered as of April 14.
The clotting disorder in the brain is called cerebral venous sinus thrombosis (CVST), which normally does not occur with low blood platelets, doctors say.
All six cases of cerebral venous sinus thrombosis with low platelet levels occurred in white females aged 18 to 48 with “no obvious patterns of risk factors detected,” said Dr. Tom Shimabukuro of the CDC’s COVID-19 Vaccine Task Force. Most people’s symptoms occurred around eight days after inoculation.
Shimabukuro said that one of the women died in March and three remain hospitalized, with two in intensive care.
The J&J vaccine was granted an emergency use authorization in February 2021 and is a one-dose shot for individuals aged 18 and older. It has been authorized for use in the European Union but the vaccine has not been delivered or administered yet.
According to Shimabukuro, the observed clotting disorders “appear to exceed expected [cases] based on background rates of CVST among women aged 20-50 years (three-fold or greater).”
Blood clots with low levels of platelets were not observed in people who received the messenger RNA vaccines by Pfizer-BioNTech and Moderna. But there were three reports of cerebral venous sinus thrombosis following the administration of 84.7 million doses of the Moderna vaccine as of April 12. The cases, however, differ from the J&J ones, since all three had normal platelet counts.
Platelets are blood cells that help the blood clot to stop bleeding. A normal platelet count is anywhere from 150,000-450,000 per microliter. “Dangerous internal bleeding can occur when your platelet count falls below 10,000 platelets per microliter,” Shimabukuro said.
Johnson & Johnson released a statement (pdf) regarding the decision taken at the emergency meeting.
“We continue to believe in the positive benefit-risk profile of our vaccine,” said Paul Stoffels, vice chairman of the Executive Committee and chief scientific officer at Johnson & Johnson. “We value the consideration of the Advisory Committee, and we will continue to collaborate with medical experts and global health authorities, including the CDC, U.S. Food and Drug Administration (FDA), European Medicines Agency, and the World Health Organization, as we work toward continuing vaccinations to end the global pandemic.”
The drug manufacturer also said that it “has made the decision to proactively delay the rollout of our vaccine in Europe and pause vaccinations in all Janssen COVID-19 vaccine clinical trials.”
Health officials still do not know the cause of the clots or the true incidence rate, although they expect more cases to be identified in the next two weeks.
“Right now we believe these events to be extremely rare, but we are also not yet certain we have heard about all possible cases, as this syndrome may not be easily recognized as one associated with the vaccine,” CDC Director Rochelle P. Walensky said at a press briefing on Wednesday.
White House COVID-19 response coordinator Jeff Zients said that the pause would not have an impact on the country’s vaccination campaign.
“I want to be clear that this announcement will not have a significant impact on our vaccination program,” Zients said. “The J&J vaccine makes up less than five percent of the more than 190 million recorded shots in the arms in the U.S. to date.”
“We are working now with our state and federal partners to get anyone currently scheduled for a J&J vaccine quickly rescheduled for a Pfizer or Moderna vaccine,” he added.
The CDC and FDA in a joint press release said individuals who received the J&J vaccine and experienced severe headache, leg pain, abdominal pain, or shortness of breath “within three weeks after vaccination should contact their health care provider.”