April 13, 2021 — After receiving reports of a rare blood clot in people receiving the Johnson & Johnson COVID-19 vaccine, the FDA and the CDC have recommended a pause in the use of the vaccine, pending further investigation.
Here, what you need to know:
Why was the pause suggested?
After reviewing data, the agencies found six reports of people who experienced rare blood clots in combination with low platelets, which are the smallest blood cells and involved in clotting. The six reports were found out of more than 6.8 million doses given. The FDA and CDC initiated the pause ''out of an abundance of caution."
What else is known?
According to a joint statement issued by the CDC and FDA, all six cases were in women between ages 18-48. Symptoms occurred 6-13 days after vaccination. The type of clot is known medically as a cerebral venous sinus thrombosis (CVST) and was seen in combination with low levels of blood platelets. Go here to learn more about these types of blood clots.
Of the six cases, one woman died; another was in critical condition.
Treatment of this type of clot is different from that for other types, the CDC and FDA say. Typically, an anticoagulant drug, heparin, is used. But for this type of clot, alternative treatment may be needed.
Why does it happen?
"We don't have a definitive answer at this time, but it appears to involve an immune response related to the J&J vaccine that adversely affects the function of the platelets, which in turn prevents the normal clotting process from occurring," says Robert Glatter, MD, emergency doctor at Lenox Hill Hospital in New York City.
He says that the explanation "may ultimately be related to the adenovirus vector [used in the vaccine] itself."
Why does it seem to affect women more than men?
That is not yet known, says William Schaffner, MD, professor of preventive medicine and infectious disease specialist at Vanderbilt University Medical Center in Nashville. "This has been true for the AstraZeneca [vaccine] as well and their blood clot issues," he says. If it is an immune-related issue, women do tend to have more of those issues than men, in general, he says.
What should people who got the J&J vaccine know and do?
Keep in mind that the reports of blood clots were rare, Schaffner suggests. The chances are about 1 in a million, based on the six reports out of 6.8 million doses given. "This is actually a testament to the sensitivity of our vaccine safety system," he says, that those few reports would be detected out of millions of doses.
People who have gotten the vaccine should be vigilant of symptoms, the FDA and CDC say. If you received the Johnson & Johnson vaccine and develop severe headache, abdominal pain, leg pain, or shortness of breath within 3 weeks of vaccination, contact your their health care provider.
How long will the pause last?
That is also not yet known. The CDC's Advisory Committee on Immunization Practices (ACIP) will meet on Wednesday to further review the cases and ''assess their potential significance." FDA is also reviewing the data further.