The biotech company said the shot was about 51% effective against the virus for kids under 2 years old and about 37% effective in kids ages 2 to 5.
It added that similar requests are underway with international regulatory authorities, noting that the requests are based on a 25-microgram two-dose primary series of the vaccine.
"We are proud to share that we have initiated our EUA submission for authorization for our COVID-19 vaccine for young children," Moderna CEO Stéphane Bancel said in a statement. "We believe mRNA-1273 will be able to safely protect these children against SARS-CoV-2, which is so important in our continued fight against COVID-19 and will be especially welcomed by parents and caregivers."
The company cited positive interim results from a March study that "showed a robust neutralizing antibody response in the 6 month to under 6 years of age group after a two-dose primary series of mRNA-1273, along with a favorable safety profile."
Each kid receives a quarter of the regular dose, but the shots triggered the same amount of virus-fighting antibodies proven to protect young adults.
There were no serious side effects, and the shots triggered fewer fevers than other routine vaccinations.
Dr. Paul Burton, Moderna’s chief medical officer, told The Associated Press that the reason for those results was the omicron variant's ability to partially evade vaccine immunity.
He said adults without boosters showed similarly less effectiveness against milder omicron infections.
Moderna said the emergency use authorization (EUA) submission for children ages 6 months to under 6 years will be complete next week.
Moderna is also currently studying booster doses for all pediatric cohorts.
While other countries have expanded the shot to kids as young as 6, the FDA had previously cited concern about a rare side effect, heart inflammation, in teen boys; it hasn’t ruled on Moderna’s earlier pediatric applications.
Right now, only children ages 5 or older can be vaccinated in the U.S., using rival Pfizer’s vaccine.
Pfizer is also expected to announce if three of its even smaller-dose shots work for the youngest children.
The Associated Press contributed to this report.