Alex Gottschalk/DeFodi Images via Getty Johnson & Johnson's COVID-19 vaccine
In a statement released on Thursday, the governmental health agency said it was limiting "the authorized use of the Janssen COVID-19 Vaccine" — otherwise known as the Johnson & Johnson vaccine — to those 18 or over with no access to other approved vaccines or for those "who elect to receive the Janssen COVID-19 Vaccine because they would otherwise not receive" a vaccine at all.
The FDA's reasoning for the move was due to "updated analysis, evaluation and investigation of reported cases," which it says "warrants limiting the authorized use of the vaccine" because of a risk of thrombosis with thrombocytopenia syndrome.
The agency explained that thrombosis with thrombocytopenia syndrome, or TTS, is a syndrome of "rare and potentially life-threatening blood clots in combination with low levels of blood platelets" that can present an onset of symptoms approximately one to two weeks following administration of the J&J vaccine.
The FDA also stipulated that "the known and potential benefits of the [Janssen or J&J] vaccine for the prevention of COVID-19 outweigh the known and potential risks" of the shot, but is nonetheless updating its materials to reflect those risks.
"We recognize that the Janssen COVID-19 Vaccine still has a role in the current pandemic response in the United States and across the global community. Our action reflects our updated analysis of the risk of TTS following administration of this vaccine and limits the use of the vaccine to certain individuals," Peter Marks, M.D., Ph.D., director of the FDA's Center for Biologics Evaluation and Research, said in the statement.
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"Today's action demonstrates the robustness of our safety surveillance systems and our commitment to ensuring that science and data guide our decisions. We've been closely monitoring the Janssen COVID-19 Vaccine and occurrence of TTS following its administration," he continued, adding that "the agency will continue to monitor the safety of the Janssen COVID-19 Vaccine and all other vaccines, and as has been the case throughout the pandemic, will thoroughly evaluate new safety information."
The statement also reiterated prior background information on the J&J vaccine, including the the April 2021 pause in its use by the FDA due to the occurrence of TTS, and subsequent lifting of that pause ten days later.
It reported that the FDA, along with the CDC, "confirmed a total of 15 cases of TTS had been reported to the Vaccine Adverse Event Reporting System (VAERS), including the original six reported cases [that prompted the pause], out of approximately 8 million doses administered" at the time.
The FDA also expanded on its updated research and analysis, writing that through March 18 of this year, the agency along with the CDC "have identified 60 confirmed cases [of TTS], including nine fatal cases" since the pandemic began and the J&J vaccine started to be offered.
The report determined "that the reporting rate of TTS is 3.23 per million doses of vaccine administered and the reporting rate of TTS deaths is 0.48 per million doses of vaccine administered" — in other words a negligible, but nonetheless present, risk.
As information about the coronavirus pandemic rapidly changes, PEOPLE is committed to providing the most recent data in our coverage. Some of the information in this story may have changed after publication. For the latest on COVID-19, readers are encouraged to use online resources from the CDC, WHO and local public health departments.