"Off-label" use of the Pfizer COVID-19 vaccine in children younger than 12 years is "not appropriate," the U.S. Food and Drug Administration warned Monday. The American Academy of Pediatrics (AAP) also "strongly discourages" such use.

On Monday, the vaccine was fully approved for use in people 16 years and older. It also has emergency use authorization for people as young as 12 years, but it still is not cleared for use in younger children.

"We do not have data on the proper dose nor do we have full data on the safety in children younger than what is in the emergency use authorization," Acting FDA Commissioner Janet Woodcock, M.D., said Monday, CNN reported. "So, that would be a great concern that people would vaccinate children because we don't have the proper dose and we don't have the safety data, nor do we have all the efficacy data, as well. We are not recommending that children younger than age 12 be vaccinated with this vaccine. It would not be appropriate."

"The clinical trials for the COVID-19 vaccine in children ages 11 years old and younger are underway, and we need to see the data from those studies before we give this vaccine to younger children," Lee Savio Beers, M.D., president of the AAP, said in a statement Monday. The adult vaccine dose is much higher than doses being tested in younger children, and the AAP "strongly discourages" off-label use of the vaccine in children younger than 12 years, the statement read.

Pfizer has said it expects to have vaccine trial data on children ages 5 to 11 years by the end of September, and data for children ages 2 to 5 years could be available shortly after, CNN reported. Moderna and Johnson & Johnson are also conducting trials of their vaccines in children.