The agency's move comes after a closely watched FDA advisory group vote earlier this week, which resulted in a unanimous vote in favor of the FDA authorizing both vaccines in this age group.
"The FDA’s evaluation and analysis of the safety, effectiveness, and manufacturing data of these vaccines was rigorous and comprehensive, supporting the EUAs," the agency said in a news release.
The data shows that the “known and potential benefits” of the vaccines outweigh any potential risks, the agency said.
The Moderna vaccine is authorized as a two-dose primary series in children 6 months to 17 years of age. The Pfizer vaccine is now authorized as a three-dose primary series in children 6 months up to 4 years of age. Pfizer’s vaccine was already authorized in children 5 years old and older.