Pfizer and BioNTech said Monday that late-stage trials of its COVID-19 vaccine in children show that the shots were safe and effective in kids aged between 5 and 11.

The results mark a key step in getting the vaccine approved for younger school-aged children.

In its press release, Pfizer said children who received low-dose shots in the Phase 2/3 trials developed virus-fighting antibodies about as well as adults who received two typical shots of the vaccine.

"We are pleased to be able to submit data to regulatory authorities for this group of school-aged children before the start of the winter season," said Dr. Ugur Sahin, BioNTech's co-founder and CEO. "The safety profile and immunogenicity data in children aged 5 to 11 years vaccinated at a lower dose are consistent with those we have observed with our vaccine in other older populations at a higher dose."

The Pfizer vaccine has already been fully approved in the U.S. for everyone aged 16 and up, and is available for those aged 12 to 15 under emergency use authorization.

Editor's note: A previous version of this story mistakenly noted that the Pfizer vaccine is fully approved for all children aged 12 and older.