Federal officials on Tuesday called for a pause on using the Johnson & Johnson COVID-19 vaccine after six women developed rare blood clots days after receiving the single-dose shots.
The U.S. Food and Drug Administration said it’s joining the Centers for Disease Control and Prevention in urging a halt on administering the single-shot vaccines.
One of the women died, and another is currently in critical condition, Dr. Peter Marks, director of the Center for Biologics Evaluation and Research at the Food and Drug Administration, said during a news conference Tuesday morning.
The CDC said its Advisory Committee on Immunization Practices is meeting Wednesday to “review these cases and assess their potential significance.” The FDA will also investigate and recommends halting the use of the vaccine until the work is finished.
Nationwide, more than 6.8 million doses of the Johnson & Johnson vaccine had been administered as of Monday, officials said.
Six people who received the shot developed “a rare and severe type of blood clot,” the FDA and CDC said in a joint news release Tuesday morning.
The reported blood clots, called cerebral venous sinus thrombosis, were all among women ages 18 and 48, the agencies said. They developed the symptoms six to 13 days after they received the vaccine.
In addition to the blood clots, the six women also experienced low blood platelet levels. The cases required treatment different than what’s typically given, officials said.
“These adverse events appear to be extremely rare,” the agencies said. ”COVID-19 vaccine safety is a top priority for the federal government, and we take all reports of health problems following COVID-19 vaccination very seriously.
Dr. Carlos del Rio, the executive associate dean at Emory University School of Medicine, told CNN on Tuesday that people who received the Johnson & Johnson vaccine should not “freak out,” because they have “a much higher chance of getting run over by a car” than developing blood clots after the shot.
“I think the first takeaway is that it’s a very rare event. I mean, you’re talking about one per million. And when you give millions of doses of vaccines, you will see events like this that you won’t see in the clinical trials just because you didn’t have millions of people involved,” del Rio told the outlet.
Still, he said, the CDC and FDA did the right thing by calling for a pause.
“Vaccine safety has always been a priority, and I think this is exactly the right move until we understand what’s going on and what’s the way forward,” he said.
Federal officials encourage people to call their doctors if they experience serious “headache, abdominal pain, leg pain, or shortness of breath” within three weeks of receiving a Johnson & Johnson vaccine.
The pause comes after “adverse reactions” to the Johnson & Johnson vaccine recently were reported at vaccination sites in at least four states.
In North Carolina, two providers temporarily said they stopped administering the vaccines last week after some people receiving the shots experienced reactions including fainting and dizziness. The sites later resumed the use of the vaccines after the CDC said there were no safety issues.
In Georgia, a vaccination site paused use of Johnson & Johnson vaccines after administering 425 doses on Wednesday. Officials said eight people who received them had “adverse reactions” that were “consistent with common reactions in adults being vaccinated with any vaccine,” McClatchy News reported.
Dr. Ashish Jha, dean of the Brown University School of Public Health, also it’s “the right step” to halt the Johnson & Johnson vaccine.
“Central to vaccination success is ensuring people have confidence they are safe,” he wrote on Twitter.
How the Johnson & Johnson vaccine works
Del Rio of Emory University said the vector, or method of delivery, of the Johnson & Johnson COVID-19 vaccine may be behind the blood clots, but he cautions there isn’t enough evidence to yet to make such a conclusion.
The shot, just like the AstraZeneca COVID-19 vaccine which has been linked to blood clots in Europeans, is a viral vector vaccine. It works by delivering a harmless DNA virus called an adenovirus that has been genetically modified so it cannot make copies of itself in humans or cause disease. This modified virus carries specific instructions into the body’s cells that teach them how to make the spike protein the novel coronavirus uses to infect people.
Cells then display the spike proteins on their surfaces like a trophy on a pedestal, which the immune system doesn’t recognize. This triggers the production of coronavirus-fighting antibodies and primes the body to protect itself against the pathogen if it comes into contact with it.
However, del Rio told CNN that evidence from Europe shows this process may be sparking the production of antibodies against platelet factor 4, a protein that is known to cause blood clots. Still, much remains unknown about the relationship between the Johnson & Johnson vaccine and the recent cases of blood clotting.
This method is different from how the Pfizer and Moderna shots work. Instead of DNA, they insert mRNA — a molecule already found in the body — which stores directions that teach our cells to make copies of the coronavirus spike protein, sparking the creation of antibodies without the assistance of a separate harmless virus.