U.S. health authorities recommended a pause in the use of Johnson & Johnson’s Covid-19 vaccine in order to investigate rare but severe cases of blood clots, a setback to vaccination efforts racing against virus variants.
The U.S. Food and Drug Administration and the U.S. Centers for Disease Control and Prevention announced the move Tuesday, after finding that six women between the ages of 18 and 48 years who got the vaccine had developed blood clots and one died.
The severe side effects were rare—more than 6.8 million doses of J&J’s shot have been administered in the U.S.—but health authorities said they moved quickly out of an abundance of caution.
“The fact that a pause was done, I think, is just a testament to how seriously we take safety,” said Anthony Fauci, the government’s top infectious-disease official.
The action prompted the U.S. government to suspend at its vaccination sites administration of J&J’s vaccine, a federal health official said, while some states and other authorities moved to administer other authorized shots. Some countries, meanwhile, also moved quickly to limit the shot’s use.