SAN FRANCISCO (KRON) — Pfizer and BioNTech have submitted data to the U.S. Food and Drug Administration on Tuesday from a trial on the effects of the COVID-19 vaccine on children between 5-12 years old.

At this time, only children as young as 12 are able to get the Pfizer vaccine.

The Phase 2/3 trial resulted in “robust neutralizing antibody responses” for the children, who received two doses that were smaller than what has been administered to everyone else. The strong immune response came one month after getting the second dose, according to the companies.

“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, CEO and co-founder of BioNTech. “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 side effects were also “generally comparable” to the ones that people who are 16-25 years old experienced, according to the companies.

The trial included 2,268 participants who were 5 to 11 years of age and received a 10 µg (microgram) dose level in a two-dose regimen.

The Pfizer COVID-19 vaccine is the only one approved by the FDA for people 16 years and up. It also has Emergency Use Authorization for kids 12-15 years old.

U.S. officials recently allowed certain populations who received the Pfizer vaccine to get booster shots — a third dose administered six months after the last dose to combat waning immunity.

The booster shot is available to eligible people who have received the two-dose Pfizer vaccine at least six months ago. They include people 65 and older as well as people over 18 who have underlying medical conditions, who work in high-risk settings and who live in high-risk settings.