Nearly 23 million eligible children have received at least one dose of the coronavirus vaccine since the most recent group of 5-to-11-year-olds got the green light late last year and started rolling up their sleeves.

But many families are anxiously awaiting a pediatric vaccine for the youngest Americans — ages 6 months through 4 years — as the omicron variant surges across the United States.

“We do need a vaccine for these kids,” said Sean O’Leary, vice chair of the Committee on Infectious Diseases for the American Academy of Pediatrics. However, a vaccine for children younger than 5 may not be available in time “to change this current wave” of infections caused by the omicron variant, which many experts say may be nearing its peak.

Pediatricians say coronavirus vaccines likely will be important well beyond this wave.

Here are some things we know about the vaccine for the youngest children.