The US Food and Drug Administration (FDA) on Monday authorized the use of the Pfizer-BioNTech COVID-19 vaccine for children aged 12 to 15 years old.
"This is a promising development in our fight against the virus," said President Joe Biden.
"If you are a parent who wants to protect your child or a teenager who is interested in getting vaccinated, today's decision is a step closer to that goal."
The FDA previously granted an emergency use authorization for the Pfizer-BioNTech vaccine to individuals aged 16 and older.
"Having a vaccine authorized for a younger population is a critical step in continuing to lessen the immense public health burden caused by the COVID-19 pandemic," said Peter Marks, director of the FDA's Center for Biologics Evaluation and Research.
The FDA said some 1.5 million COVID-19 cases in individuals aged 11 to 17 years old have been reported to the U.S. Centers for Disease Control and Prevention between March 1, 2020 and April 30, 2021.
The course of the disease is generally milder in children but they can pass it on to older, more vulnerable adults.
Pfizer and its partner BioNTech said in March that their two-dose vaccine regimen was shown to be safe and highly effective in a trial of 2,260 12 to 15-year-olds.
Biden last week stressed the importance of expanding vaccinations to 12 to 15-year-olds and said the authorities were "ready to move immediately" once the authorization came through.
Some 20,000 pharmacies around the country were ready to begin to vaccinate adolescents, he said, and doses will also be shipped to pediatricians.
Covid-19 vaccines from Moderna and Johnson & Johnson have also received emergency use authorizations from the FDA but only for individuals over the age of 18.
Acting FDA commissioner Janet Woodcock described Monday's move as a "significant step in the fight against the COVID-19 pandemic."
"Today's action allows for a younger population to be protected from Covid-19, bringing us closer to returning to a sense of normalcy and to ending the pandemic," Woodcock said in a statement.
"Parents and guardians can rest assured that the agency undertook a rigorous and thorough review of all available data, as we have with all of our COVID-19 vaccine emergency use authorizations," she added.