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The US Food and Drug Administration has limited the use of Johnson & Johnson’s single-shot coronavirus vaccine due to the small risk of developing a rare and potentially life-threatening blood clotting disorder. 

In a statement released yesterday (May 5), the FDA said it is limiting the emergency use authorization of the vaccine. Now, adults can only take the Johnson & Johnson shot if other vaccines are not readily available or medically appropriate—for example, if they have had allergic reactions to other coronavirus vaccines. Patients may also receive the J&J vaccine if they refuse to take another shot. (The shot was never authorized for adolescents or children.)

The J&J vaccine is associated with a sometimes fatal condition called thrombosis with thrombocytopenia syndrome (TTS). According to the FDA statement, an updated analysis of safety data through March 18 found that there have been 60 confirmed cases of TTS after J&J vaccinations, with nine resulting in death. That’s out of roughly 17 million people who have gotten the J&J vaccine, according to The Washington Post, for a rate of about three cases for every million doses administered. When it occurs, this side effect usually manifests within one to two weeks of vaccination and is commonly treated with heparin, an anti-clotting agent that can cause severe bleeding. 

“If we see deaths and there is an alternative vaccine that is not associated with deaths but is associated with similar efficacy . . . we felt it was time at this point to make a statement on the [product’s] fact sheet that this was not a first-line vaccine,” Peter Marks, director of the FDA’s Center for Biologics Evaluation and Research, tells STATThe ninth TTS death associated with the J&J shot occurred in the first quarter of this year, prompting the FDA to limit the vaccine’s use, reports STAT.

Marks notes that other, safer vaccines can continue to be used to inoculate people against the coronavirus. Already, more than 202 million have received two doses of the authorized COVID-19 vaccines from Pfizer-BioNTech and Moderna, according to the Post. 

The J&J vaccine, initially conceived as a one-shot alternative to these mRNA vaccines, was authorized in February of last year. But the use of the vaccine has slumped due to the risk of blood clots, production issues, and lower efficacy than the Moderna and Pfizer options, reports Reuters. US health authorities paused the use of the shot in April 2021 due to the potential risk of blood clots but resumed its use 10 days later, saying that the benefits of the vaccine outweighed the risks. In December, the Centers for Disease Control and Prevention recommended that other vaccines be used instead of J&J.

J&J has updated its own fact sheet for the vaccine as well. “Data continue to support a favorable benefit-risk profile for the Johnson & Johnson Covid-19 vaccine in adults, when compared with no vaccine,” the company writes.

See “Blood Clot Risk from COVID-19 Higher than After Vaccines: Study