Federal health agencies on Tuesday recommended pausing the use of the Johnson & Johnson vaccine after a small number of people experienced “a rare and severe type of blood clot” after receiving the shot.
The Food and Drug Administration and the Centers for Disease Control and Prevention issued a statement saying they were “recommending a pause in the use of this vaccine out of an abundance of caution.”
Some 6.8 million people have received the single-shot vaccine in the United States. Of these, six have experienced the clot, the agencies said, adding: “Right now, these adverse events appear to be extremely rare.”
The news was first reported by The New York Times.
In a statement, Johnson & Johnson said it was aware that blood clots had been reported with some Covid-19 vaccines, but that “no clear causal relationship has been established between these rare events” and its shot.
“We continue to work closely with experts and regulators to assess the data and support the open communication of this information to healthcare professionals and the public,” it said.
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The six people who experienced clots were all women between the ages of 18 and 48, the FDA and CDC said. They had what’s called a cerebral venous sinus thrombosis, or CVST, as well as low levels of blood platelets.
“Treatment of this specific type of blood clot is different from the treatment that might typically be administered,” the statement said. Clots are usually treated with an anticoagulant called heparin — but that drug might be dangerous to use on CVST, it said.
The CDC will convene Wednesday a meeting of its Advisory Committee on Immunization Practices, which provides guidance on vaccines.
It said that committee would “further review these cases and assess their potential significance,” while the FDA would also investigate. “Until that process is complete, we are recommending this pause,” the joint statement said. The FDA is set to hold a news conference at 10 a.m. ET Tuesday.
The call for a pause mirrors a situation that played out in Europe last month.
Some European governments paused the rollout of the Oxford University-AstraZeneca vaccine after a similarly tiny number of people suffered CVST blood clots. The AstraZeneca vaccine uses the same type of technology as the Johnson & Johnson shot.
Most European countries have since resumed administering the shot, but with a messy patchwork of different age restrictions and other guidelines. There is some evidence that as a result of this widely publicized fear, public trust in this vaccine is lower than others that are available.
The situation in Europe has divided experts, with some saying that governments could not ignore the possible link, and others saying that the pause may have increased infections and hesitancy, damage that far outweighs the dangers from these extremely rare side-effects.