Moderna says it will ask the Food and Drug Administration to authorize two kid-sized doses of its COVID-19 vaccine for children under 6 years old, after interim results from the company’s trials showed some efficacy against infections during the Omicron wave and no new safety concerns. 

Vaccine efficacy was 37.5% in children ages 2 to 6, the company said Wednesday, and 43.7% in children 6 months to 2 years old. Blood samples from clinical trial participants showed the vaccine had a “robust neutralizing antibody response in both age groups.” 

“Given the need for a vaccine against COVID-19 in infants and young children we are working with the U.S. FDA and regulators globally to submit these data as soon as possible,” said Stéphane Bancel, Moderna’s CEO, in a release announcing the new results. 

Bancel said Moderna also would be submitting data to the FDA for vaccinating older age groups of children. Moderna’s vaccine is currently available for ages 18 and up.

The company’s original request to vaccinate adolescents with two 100 microgram doses, the same as adults, has been stalled for months over the FDA’s concerns around rare heart inflammation side effects. The vaccine tested for younger kids is only 25 micrograms per dose. Moderna says it also plans to study a booster dose in children. 

Moderna’s announcement comes a month after Pfizer and BioNTech said they would delay submission of data from their COVID-19 vaccine trials for the youngest age groups, citing disappointing data against Omicron from two kid-sized doses of their vaccine. Data from testing three doses of that vaccine are expected “in early April.” 

The Biden administration had planned in February to roll out around 10 million doses, following the FDA’s authorization and recommendations from the Centers for Disease Control and Prevention, which must also sign off on eligibility.

“Unfortunately, it was found that that regimen was not adequate enough to give what was felt to be an appropriate or optimal immune response with protection, and so it looks like this almost certainly will be a three‑dose vaccine for children in that age cohort. And that’s the reason why it’s taking so long, as it were,”  the president’s chief medical adviser, Dr. Anthony Fauci, said Tuesday during an event hosted by The Washington Post. 

The FDA had initially planned to convene its outside advisers on February 15 to weigh the benefits and risks of BioNTech and Pfizer’s request. The same panel — the Vaccines and Related Biological Products Advisory Committee — is already scheduled to meet in two weeks to discuss COVID-19 vaccine booster shots. 

Millions of children under 5 have caught COVID-19 and more than 400 have died, according to CDC data. 

“Certainly, the FDA, as they always do, want to get it right. So, when they approve something, one can be certain that it’s effective as well as safe,” Fauci said.