FDA joins Europe in probing rare blood clots after Johnson & Johnson's COVID-19 vaccine

Drug regulators in Europe last week flagged rare but “serious” cases of blood clots in people who had received Johnson & Johnson’s COVID-19 vaccine. But it’s not just European regulators taking a close look at the shot’s safety profile—the FDA is, too. 

The FDA is “aware of reports in the U.S. of serious thromboembolic events” and has “not found a causal relationship with vaccination,” a spokeswoman said late Friday. The agency is continuing its investigation of the reports, which will “inform the potential need for regulatory action.” 

Late last week, European Medicines Agency (EMA) officials said they were investigating three cases of unusual blood clots with low blood platelets following vaccination with J&J’s shot. Another case came in a clinical trial. One of the cases was fatal. 

A J&J spokeswoman said the company is working with regulators as more data come in and supports the "open communication" of any new findings with healthcare providers so they can monitor for risks. 

J&J "is aware" that serious blood clots, including those associated with low platelet levels, have been reported "with all COVID-19 vaccines," a company spokeswoman said.

"Our close tracking of side effects has revealed a small number of very rare events following vaccination," she said. "At present, no clear causal relationship has been established between these rare events and the Janssen COVID-19 vaccine." 

In all, the reports “point to a ‘safety signal,’ but it is currently not clear whether there is a causal association," the EMA's Pharmacovigilance Risk Assessment Committee said last week.

The group will decide whether any regulatory steps, such as a warning about side effects, are appropriate. For its part, the FDA says it shared information about the U.S. reports with the EMA, which formed "the basis" of the EMA's announcement

RELATED: Johnson & Johnson's COVID-19 vaccine under scrutiny at EMA after 4 'serious cases' of unusual blood clots 

As with other vaccines, regulators are continuously tracking safety for COVID-19 shots. The FDA aims to “quickly identify any specific safety concerns that may arise, and we will keep the public updated as we learn more,” the agency spokeswoman said.

Since the J&J vaccine’s emergency use authorization in the U.S. in late February, 6.5 million doses have been administered, according to the latest Centers for Disease Control and Prevention data. 

Europe approved J&J’s vaccine last month, but the rollout has not yet kicked off there.  

RELATED: Johnson & Johnson takes control at troubled Emergent vaccine plant after major production snafu 

Amid the questions around rare clots, J&J’s U.S. vaccine rollout has run into other snags. Just 700,000 doses are set to ship to states this week, The Wall Street Journal reported Friday, while multiple sites have temporarily closed after vaccine recipients suffered negative reactions to the shot, CBS News reports.

Plus, J&J is now backing off from a prior target to deliver 24 million doses by the end of April, The Washington Post reports.

When news surfaced that J&J’s manufacturing partner, Emergent BioSolutions, ruined a large batch of the vaccine, the company insisted it would work with U.S. authorities to deliver 24 million doses by the end of this month. Now, the company is focusing on a target of 100 million doses by the end of May, according to the newspaper.