On Sunday, the US Food and Drug administration said that it is reviewing reports that the Moderna COVID-19 vaccine can cause heart issues in some adolescents.
In a statement given on Sunday, Moderna said the FDA "requires additional time to evaluate recent international analyses of the risk of myocarditis after vaccination."
According to the New York Times, Moderna had requested authorization from the FDA back in June for the use of its vaccine in children ages 12 to 17 years, but has yet to receive a ruling on the application.
Adolescents would receive the same dosage as adults, 100 micrograms.
In July, the European Medicines Agency approved the vaccine for use in adolescents, but since then, several European countries have paused its use in people 30 and younger over concerns about myocarditis, which is an inflammation of the heart muscle.
More than 1.5 million adolescents around the world have received the COVID-19 vaccine, said Moderna, but data so far does not suggest an increased risk of myocarditis.
Studies from the US and Israel though have both linked the Pfizer-BioNTech and Moderna to rare cases of myocarditis, noting a higher risk for the Moderna vaccine.
The FDA notified Moderna about the need for more time on Friday, with the company revealing that a decision may not come until January of 2022.
"The agency took roughly a month to authorize the Pfizer-BioNTech vaccine for children ages 12 to 15 years. That vaccine has been available to adolescents in the United States and Europe since May," wrote the New York Times.
Dr. Paul Offit, director of the Vaccine Education Center at Children's Hospital of Philadelphia and a member of the FDA's vaccine advisory committee, said that vaccine-caused myocarditis.
COVID-19 is more likely to cause myocarditis, Dr. Offit said, because the virus can infect and damage the lining of the heart. "That would be the decision point I would make for my child," he said.
In the American and Israeli studies, the incidence of heart problems who had received either the Pfizer-BioNTech or the Moderna were highest in males aged 16 to 29 years, with the risk declining in younger children.
The revelation comes as the FDA authorized the Pfizer-BioNTech vaccine for children aged 5 to 11.