Europe's equivalent of the FDA is investigating whether four blood-clotting events are linked to Johnson & Johnson's COVID-19 vaccine, the agency said April 9.
The European Medicines Agency, the European Union's drug regulator, said four serious cases of "unusual blood clots with low blood platelets" have been reported in people after receiving a Johnson & Johnson vaccine. It's unclear if there's a causal link.
One of the four cases was in a clinical trial, though the agency didn't say where that trial was taking place. The other three were in people vaccinated in the U.S. The U.S. is the only country using the Johnson & Johnson vaccine.
One of the four people died, the agency said.
About 4.9 million people have been vaccinated with Johnson & Johnson's vaccine as of April 8, according to the CDC.
"Our close tracking of side effects has revealed a small number of very rare events following vaccination," Johnson & Johnson said in a statement to The New York Times. "At present, no clear causal relationship has been established between these rare events and the [Johnson & Johnson] COVID-19 vaccine."
The FDA said in a statement sent to Becker's Hospital Review: "FDA is aware of reports in the U.S. of serious thromboembolic events, sometimes associated with thrombocytopenia (low levels of platelets in the blood) that have occurred in a few individuals following receipt of the [Johnson & Johnson] COVID-19 Vaccine. Both conditions can have many different causes. At this time, we have not found a causal relationship with vaccination and we are continuing our investigation and assessment of these cases. Our analysis of the data will inform the potential need for regulatory action."
The FDA added that it provided information to the European Medicines Agency about the reports of blood clots, which is the basis for the agency's investigation.
Earlier this week, the European Medicines Agency said blood clots should be listed as a very rare side effect of AstraZeneca's vaccine. The benefits of that vaccine still outweigh the risks, the agency concluded.
Blood clots are common in the general population, according to the Times. Between 300,000 and 600,000 people in the U.S. develop blood clots in their lungs or in veins in the legs or other parts of the body each year, according to CDC data.
Editor's note: This article was updated April 12 at 3:45 p.m. CT to include a statement from the FDA.
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