If you are one of the almost 7 million Americans who have received the Johnson & Johnson COVID-19 vaccine, there are suddenly questions and concerns about its safety.
In the midst of a mass vaccination campaign, the Food and Drug Administration and the Centers for Disease Control and Prevention on Tuesday recommended a pause in the use of the vaccine “out of an abundance of caution."
The agencies are reviewing data involving six U.S. cases of a rare and severe type of blood clot in women who had received the shot a number of days prior. One case was fatal and one patient is in critical condition.
“I don’t think I can overstate how serious this development is,” said NBC News medical contributor Dr. Natalie Azar.
“Certainly, I can understand why this has anyone who has received the vaccine and certainly regulators are very, very concerned… (but) it’s so important to point out — I really want to reinforce this — that these are very, very rare events.”
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Here’s what you need to know:
What’s the main concern?
The six cases — out of 6.8 million doses given in the U.S. — involve a “rare and severe” type of blood clot called cerebral venous sinus thrombosis, which was seen in combination with low levels of blood platelets, the FDA and CDC said in a joint statement. All of the cases involve women between the ages of 18 and 48, and the symptoms occurred 6 to 13 days after vaccination. Dr. Anne Schuchat, principal deputy director of the CDC, described it as a "stroke-like" illness.
“These are not the typical blood clots we usually think of in the leg, for example — those occur with a frequency of hundreds of thousands per year,” Azar noted. “Rather, these are rarer events… a blood clot in the veins of the brain that are thought to be perhaps triggered by an immune reaction. That’s why we’re seeing this predominantly in younger women.”
Birth control could play a part — health officials just don’t know yet, she added.
Usually, the anticoagulant drug heparin is used to treat blood clots, but that could actually be dangerous for this clot in the brain, so alternative treatments must be given, the FDA and CDC said.
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Why didn’t the clinical trials for the vaccine alert about this problem?
A phase 3 clinical trial enrolls tens of thousands of participants, while millions of people are now being vaccinated, Azar explained. That means some adverse events may not become apparent until after the clinical trial.
“Unfortunately, sometimes these rarer events can emerge,” she noted.
When they do occur, most adverse events happen relatively quickly after the vaccination.
What symptoms should a person watch for?
If you’ve received the J&J vaccine recently, contact your doctor if you develop a severe headache, abdominal pain, leg pain or shortness of breath within three weeks after the shot, the FDA and CDC advised.
"Don't get an anxiety reaction; however, pay attention. Do you have symptoms?" Dr. Anthony Fauci said during a news conference at the White House. "Watch out for not feeling very well."
The symptoms of a low platelet count would be easy bruising, nose bleeding and gum bleeding, Azar added.
The risk of experiencing these "clotting events" is very low for people who received the vaccine more than a month ago, Schuchat said.
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What if you're scheduled to receive the J&J vaccine?
CDC partners will be working to reschedule these appointments in the days ahead, Schuchat said. "This may be a bit bumpy," she added.
In the vast majority of people, the benefit of the J&J vaccine would far outweigh this risk, Azar said.
“The problem is that we don’t yet know how to identify somebody who would be at risk other than to say that it appears to occur in younger people and more predominantly in females,” she noted.
“I don’t think we can say that this isn’t a significant setback. The Johnson & Johnson vaccine really will continue to be, I think, a part of a powerful tool in the arsenal. We’re just very fortunate that we still have such a good and significant buffer with both of the mRNA vaccines.”