A U.S. health advisory panel on Wednesday is set to review six reported cases of rare blood clots in women who received Johnson & Johnson‘s COVID-19 vaccine one day after federal regulators paused the use of the shot to assess the issue.
The six cases, in women aged between 18 and 48, were reported out of 7.2 million doses of the J&J vaccine administered in the United States, and were a risk U.S. officials and immunology experts said appeared extremely low, given the novel coronavirus’s heavy toll.
J&J’s single-dose shot is less widely used across the country compared to the 185 million doses delivered of Moderna and Pfizer/BioNTech’s two-shot vaccines, but has been seen as a critical option to expand protections to harder-to-reach populations.
The U.S. Centers for Disease Control and Prevention’s immunization experts will review the clotting cases and vote on recommendations for future use of the shot. The Food and Drug Administration, which approved the vaccine, will then review the analysis and determine the next steps.
The administration of President Joe Biden said on Tuesday it did not expect the pause in the vaccine’s use to impact its fight against the pandemic, as it has enough doses of the two other vaccines to stay on track. The FDA said the halt should only last a few days and would also help physicians understand and address any clot risk.
Dr. Anthony Fauci, Biden’s chief medical officer, said on Wednesday the pause would allow regulators to see if there were other possible clot cases.
Asked if thought there could be many more clotting cases, he told CNN, “No, I don’t.”
The FDA’s pause “very well may be quite temporary,” he said separately on MSNBC. Following the CDC review, the FDA could decide to resume use of J&J’s vaccine, allow its use with some changes, or decide against its continued use, he said.
Fauci said it was up to the regulatory agency but that “very likely, they’ll say we looked at it, and now we will go back, maybe make some modifications.”
J&J has said that no clear causal relationship has been established between the clots and its vaccine, but that it was working closely with regulators in the United States and Europe, where it also voluntarily paused its rollout.
Its shares were down less than 1% in premarket U.S. trading on Wednesday, after closing down 1.3% on Tuesday.