At least 600,000 children, ages 12 to 15, have received their first dose of the Pfizer-BioNTech COVID-19 vaccination, Dr. Rochelle Walensky, director of the Centers for Disease Control and Prevention, said during a media briefing Tuesday.
The count comes just over a week after the Food and Drug Administration greenlighted it for emergency use in this age group, a total of 17 million in the U.S. — though many major pharmacies and hospitals did not start administering the shots until last Thursday, after the CDC also signed off on it.
Only Pfizer's COVID-19 vaccine is authorized for use in children under 18. As of Tuesday, about 3.5 million people younger than 18 have been vaccinated, according to CDC data. (During the briefing, Walensky said that 4.1 million people under 18 had been vaccinated, which the agency later told NBC News was a clerical error in her remarks.)
As of May 13, more than 3.9 million cases of the illness had been reported among children, according to the American Academy of Pediatrics. That represents about 14 percent of all COVID-19 cases in the U.S.
While young people have a much lower risk of severe COVID-19 than older adults, they can, in some cases, become very ill, and 308 children have died.
About 3,700 children with COVID-19 have gone on to have what's known as multisystem inflammatory syndrome in children, or MIS-C. The condition generally develops several weeks after a minor case of the illness and results in inflammation of various organs, including the heart, lungs, kidneys, the brain and the gastrointestinal system.
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During Tuesday's media briefing, members of the Biden administration strongly encouraged vaccinations for young people.
"The pandemic disrupted your schooling, your job search, your income, your social lives," Andy Slavitt, a COVID-19 adviser to the administration, said. "You've seen and experienced stress in a way you probably haven't before.
"Your generation has showed us how you make the world a better place," he said. "Getting vaccinated is part of carrying the mantle of becoming the generation that changes things for the better."
This story first appeared on NBCNews.com.