Update (April 23, 2021):
A Centers for Disease Control and Prevention (CDC) advisory panel voted today to resume the use of the Johnson & Johnson COVID-19 vaccine.
The vaccine rollout has been on hold for more than a week while experts at the CDC and Food and Drug Administration (FDA) reviewed data suggesting the shots may cause rare blood clots and low platelet counts. This combination of issues is now referred to as thrombosis with thrombocytopenia syndrome (TTS).
Out of nearly 8 million doses of the vaccine that have been administered in the U.S. so far, the experts identified 15 confirmed cases of TTS. All of the cases occurred in women and 13 of them occurred in women between the ages of 18 and 49. But there are other cases (including some in men) that are under review, the experts said. There have not been any reports of people developing TTS after getting the Pfizer/BioNTech and Moderna mRNA vaccines.
After hours of careful deliberation, the CDC’s Advisory Committee on Immunization Practices decided that the best course of action would be to begin using the Johnson & Johnson vaccine again in adults aged 18 and older. The committee voted to end the pause and resume the use of the vaccine with a warning added to the emergency use authorization that the vaccine may cause rare blood clots in women under 50, STAT reports. But the committee decided not to specifically restrict the use of the vaccine to specific groups, leaving the public and their health care providers to decide what’s best for them.
To learn more about the first cases of TTS that experts identified and why the CDC and FDA recommended the pause, continue to our original report below.
Original report (April 13, 2021):
Today the Centers for Disease Control and Prevention (CDC) and Food and Drug Administration (FDA) are recommending that the U.S. pauses Johnson & Johnson COVID-19 vaccinations due to concerns that the vaccine may increase the risk for a rare type of blood clot. It’s not clear yet if the vaccines are really causing the issues, but public health officials called for the temporary pause “out of an abundance of caution” while these two agencies investigate the possible link.
The recommendation comes as the CDC and FDA are reviewing six cases of rare blood clots in the brain (cerebral venous sinus thrombosis) and low platelet counts, including one death, among women who received the Johnson & Johnson vaccine, according to a CDC announcement. All the cases occurred in women who were between the ages of 18 and 48, and they all developed symptoms of these conditions between 6 and 13 days after getting the shot. As a reminder, there have been about 6.8 million doses of the vaccine given in the U.S. so far, so we are talking about just six cases out of nearly seven million doses.
Now, a CDC advisory panel will meet this week to review the cases, as will the FDA. “Until that process is complete, we are recommending a pause in the use of this vaccine out of an abundance of caution,” the CDC says. “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.”
More common types of blood clots are treated with blood thinner medications like heparin, but people experiencing these blood clots may need a different type of treatment (such as anti-seizure medications and procedures to reduce pressure in the brain, Johns Hopkins Medicine explains). So the pause is intended to give the medical community time to adjust as well as prepare for a possible need to be on the lookout for these clots and to administer those alternative treatments if needed.
The situation is strikingly similar to the issues that occurred with the AstraZeneca COVID-19 vaccine. In mid-March, countries across Europe put the rollout of that vaccine on pause after reports of people developing blood clots in the brain (including one death) after getting the AstraZeneca shots. After an investigation, the European Medicines Agency (EMA) concluded that the vaccine may be linked to an increased risk for a very rare type of blood clot and will require it to come with a warning for people with low blood platelet levels. But the EMA also said that the benefits of getting vaccinated outweigh the risks for most people.
Unlike the two mRNA vaccines that are available in the U.S., both the AstraZeneca and Johnson & Johnson vaccines rely on a modified version of an adenovirus to elicit a protective immune response in the body. But it’s not clear what exactly about the vaccines is responsible for the blood clot risks—or if it’s the same thing for both vaccines.
For people who may be concerned about this news, experts want to emphasize just how rare these blood clots seem to be. “These events (central venous thrombosis) are VERY rare, 6 out of 7 million,” Ashish K. Jha, M.D., MPH, dean of the Brown University School of Public Health, said on Twitter. “No vaccine (or drug) is perfect. But confidence is built on having a system that takes adverse events seriously, investigates them, makes data-driven decisions. That’s what FDA/CDC doing, and it’s right.”
“This is an extremely rare (less than 1 in a million) ‘safety signal.’ It’s normal for FDA to investigate, and to pause while it does out of caution,” Angela Rasmussen, Ph.D., a virologist at Georgetown University Center for Global Health Science and Security, said on Twitter. “I got the J&J vaccine 8 days ago. I’m not losing sleep over this.”
As a reminder, COVID-19 can also cause blood clots—especially among hospitalized patients. Several recent studies suggest that as many as 20% to 30% of hospitalized COVID-19 patients develop blood clots. As the CDC and FDA learn more about what may be going on in these cases, the agencies may ultimately decide that the benefits of protecting against coronavirus infections with the vaccine outweigh the potential risks.
Although having to pause vaccinations with the Johnson & Johnson is certainly not ideal, it is unlikely to have a huge impact on the overall vaccination rollout right now, Ben Wakana, director of strategic communications and engagement for the White House COVID-19 Response Team, said on Twitter. “We’re pushing out 25M Pfizer and Moderna doses each week, J&J=less than 5% of the shots in arms in the U.S.”
This temporary pause in vaccinations represents a challenging but important step in making sure that it’s as safe as possible to get these shots.