The European Union’s medicines regulator said on Tuesday that there is a “possible link” between Johnson & Johnson’s COVID-19 vaccine and blood clots, but said its “overall benefit-risk remains positive.”
At a meeting on Tuesday, the safety committee of the European Medicines Agency (EMA) concluded that a warning about unusual blood clots should be added to the product information for COVID-19 Vaccine Janssen, which was developed by Janssen, a subsidiary of Johnson & Johnson.
— EU Medicines Agency (@EMA_News) April 20, 2021
The blood clot events should be listed as “very rare side effects” of the vaccine, the committee said.
The committee said it took into consideration “all currently available evidence” including eight reports from the United States of serious cases of unusual blood clots associated with low levels of blood platelets, one of which had a fatal outcome.
All these cases occurred within three weeks after vaccination in people under 60, most of whom were women.
The EMA said “specific risk factors” have not been confirmed based on available information.
The safety committee noted that the blood clots occurred “mostly at unusual sites” such as in veins in the brain and the abdomen as well as in arteries, together with low levels of blood platelets and sometimes bleeding.
The committee said one plausible explanation is “an immune response, leading to a condition similar to one seen sometimes in patients treated with heparin called heparin induced thrombocytopenia, HIT.”
The EMA said healthcare professionals and people who will receive the vaccine “should be aware of the possibility of very rare cases of blood clots combined with low levels of blood platelets occurring within three weeks of vaccination.”
But it emphasized that the cases are “very rare” and the overall benefits of the vaccine in preventing COVID-19 “outweigh the risks of side effects.”
The United States authorized Johnson & Johnson’s shot last month and has administered over 7 million doses as of April 13.
The shot was authorized in the European Union on March 11 but the roll-out of the shots has not started yet.
Another COVID-19 vaccine, from the UK-based AstraZeneca, was previously investigated by the European Medicines Agency after reports of post-vaccination blood clots.
The agency concluded on April 7 that there was a “possible link” between the vaccine and clots but recommended countries still use the jab, ruling the benefits outweigh the risks.
The EMA said on Tuesday that the blood clots cases associated with the Janssen vaccine were “very similar” to the cases that occurred after vaccination with the AstraZeneca jab.
Zachary Stieber and Jack Philips contributed to this report.