The Food and Drug Administration and Centers for Disease Control and Prevention on April 13 recommended that use of the Johnson & Johnson COVID-19 vaccine be paused after reports of blood clots in patients receiving the shot, the agencies have announced.
In a statement, FDA said 6.8 million doses of the J&J vaccine have been administered and the agency is investigating six reported cases of a rare and severe blood clot occurring in patients who received the vaccine.
The pause is intended to give time to alert the public to this "very rare" condition, experts said during a joint CDC-FDA media briefing April 13.
"It was clear to us that we needed to alert the public," Janet Woodcock, MD, acting FDA commissioner, said. The move also will allow "time for the healthcare community to learn what they need to know about how to diagnose, treat and report" any additional cases.
The CDC will convene a meeting of the Advisory Committee on Immunization Practices on April 14 to review the cases.
Of the six reported cases linked to the J&J vaccine, all are in women between the ages of 18 and 48 years, one woman died, and another ended up in critical condition.
"I know the information today will be very concerning to Americans who have already received the Johnson & Johnson vaccine," said Anne Schuchat, MD, principal deputy director at the CDC.
"For people who got the vaccine more than one month ago, the risk is very low at this time," she added. "For people who recently got the vaccine, in the last couple of weeks, look for symptoms."
Headache, leg pain, abdominal pain, and shortness of breath were among the reported symptoms. All six cases arose within 6 to 13 days of receipt of the Johnson & Johnson vaccine.
Traditional treatment dangerous
Importantly, treatment for traditional blood clots, such as the drug heparin, should not be used for these clots. "The issue here with these types of blood clots is that if one administers the standard treatment we give for blood clots, one can cause tremendous harm or it can be fatal," said Peter Marks, MD, director of the FDA Center for Biologics Evaluation and Research.
If health care providers see people with these symptoms along with a low platelet count or blood clots, they should ask about any recent vaccinations, Dr. Marks added.
Headache is a common side effect of COVID-19 vaccination, Dr. Marks said, but it typically happens within a day or two. In contrast, the headaches associated with these blood clots come 1 to 2 weeks later and were very severe.
Not all of the six women involved in the events had a pre-existing condition or risk factor, Dr. Schuchat said.
Severe but 'extremely rare'
To put the numbers in context, the six reported events occurred among millions of people who received the Johnson & Johnson vaccine to date.
"There have been six reports of a severe stroke-like illness due to low platelet count and more than six million doses of the Johnson & Johnson vaccine have been administered so far," Dr. Schuchat said.
"I would like to stress these events are extremely rare," Dr. Woodcock said, "but we take all reports of adverse events after vaccination very seriously."
The company response
Johnson & Johnson in a statement said, "We are aware of an extremely rare disorder involving people with blood clots in combination with low platelets in a small number of individuals who have received our COVID-19 vaccine. The United States Centers for Disease Control (CDC) and Food and Drug Administration (FDA) are reviewing data involving six reported U.S. cases out of more than 6.8 million doses administered. Out of an abundance of caution, the CDC and FDA have recommended a pause in the use of our vaccine."
The company said they are also reviewing these cases with European regulators and "we have made the decision to proactively delay the rollout of our vaccine in Europe."
Overall vaccinations continuing apace
"This announcement will not have a significant impact on our vaccination plan. Johnson & Johnson vaccine makes up less than 5% of the recorded shots in arms in the United States to date," Jeff Zients, White House COVID-19 Response Coordinator, said in a statement.
"Based on actions taken by the president earlier this year, the United States has secured enough Pfizer and Moderna doses for 300 million Americans. We are working now with our state and federal partners to get anyone scheduled for a J&J vaccine quickly rescheduled for a Pfizer or Moderna vaccine," he added.
The likely duration of the pause remains unclear.
"I know this has been a long and difficult pandemic, and people are tired of the steps they have to take," Dr. Schuchat said. "Steps taken today make sure the health care system is ready to diagnose, treat and report [any additional cases] and the public has the information necessary to stay safe."
A version of this article first appeared on WebMD.com.
This article was updated 4/13/21.