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April 20, 2021
2 min read

European regulators recommend adding blood clot warning to J&J vaccine

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European regulators said Tuesday that a warning about unusual blood clots with low blood platelets should be added to information about the Johnson & Johnson COVID-19 vaccine but also that the benefits of the vaccine outweigh the risks.

The European Medicines Agency (EMA) said it reviewed a small number of cases of cerebral venous sinus thrombosis (CVST) with thrombocytopenia that occurred in people who received the one-dose vaccine in the United States, including one person who died.

Johnson and Johnson COVID vaccine
European regulators recommended adding a warning about rare blood clots to Johnson & Johnson’s COVID-19 vaccine.
Source: Adobe Stock

U.S. officials recommended last week that the rollout of the vaccine in the U.S. be paused while experts reviewed the rare events. The CDC’s Advisory Committee on Immunization Practices will meet again on Friday this week to review its recommendation about the vaccine after deciding not to hold a vote last week in order to gather more information.

Six reported cases of CVST with thrombocytopenia occurred among people who received the vaccine during the U.S. rollout, all of them women aged between 18 and 48 years who experienced symptoms within 6 to 13 days, according to U.S. officials. The cases occurred among the first 6.8 million doses of vaccine administered in the U.S. Two more cases were reported by Johnson & Johnson from phase 3 trial last year — one in a male participant aged 25 years who received the vaccine, and one in a 24-year-old female who was in the placebo arm.

In a statement, the EMA said its safety committee “concluded that these events should be listed as a very rare side effect of the vaccine.”

“Health care 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,” the EMA said. “COVID-19 is associated with a risk of hospitalization and death. The reported combination of blood clots and low blood platelets is very rare, and the overall benefits of [the Johnson & Johnson vaccine] in preventing COVID-19 outweigh the risks of side effects.”

In response, Johnson & Johnson said it would update the vaccine’s packaging to include information on diagnosing and managing the rare clotting events and would resume shipping the vaccine to Europe.

The EMA reached a similar conclusion about AstraZeneca’s COVID-19 vaccine, which also has been linked to unusual blood clots, leading some European countries to stop using it.

Both vaccines use a modified adenovirus — a human vector in the Johnson & Johnson vaccine and a chimpanzee vector in the AstraZeneca vaccine — and experts have said the similar pattern of clotting may indicate that it is an issue related to the type of vaccine.

[Editor’s note: This story was updated to note that Johnson & Johnson has resumed shipping doses of the vaccine to Europe.]