A 4-year-old receives a Covid-19 vaccine for children under 5 years old at Skippack Pharmacy in Schwenksville, Pennsylvania, June 21, 2022.
CNN  — 

Approximately 300,000 children under the age of 5 in the US – about 2% of that age group – have received at least one shot of the Covid-19 vaccine since it was recommended by the US Centers for Disease Control and Prevention last month, a senior White House official told CNN Thursday, a number the official says aligns with expectations, though is lower than other age groups.

The US Food and Drug Administration gave emergency use authorization on June 17 for both the Pfizer/BioNTech and Moderna vaccines for young children. Vaccine advisers to the CDC voted unanimously on June 18 to support recommending Covid-19 vaccination for children as young as 6 months and vaccine administration began shortly after that.

A senior White House official told CNN Thursday’s data was “very much in line” with the Biden administration’s expectations for this age group, though it was significantly behind the pace of other age brackets.

“It’s predicated on a couple of things: In particular, how parents tend to make these kinds of decisions. The overwhelming majority want to get their kids vaccinated in the pediatrician’s office or family provider’s office and about half say they prefer to do that during an annual wellness visit or routine visit and so that’s how they’re used to vaccinating their kids,” the senior official said, adding that the administration expects that number to continue to grow over months as families complete those annual check-ups.

The uptake for the 6-month-to-5-year-old age group is behind the pace of the 5-to-11-year-old age group in the same time frame, which the official attributed to demographic differences in these age groups.

“We expected this to be a little bit slower even than 5 to 11, which was slower than 12 to 17, which was slower than adults. You know, it’s just kind of what we anticipated, and what we prepared for,” the official said.

In the three weeks following the authorization of vaccines for the 5-to-11 age group, 15% of that population had received at least one shot, compared with 2% of the 6-months-to-5-years group.

Officials had previously warned that the nation’s youngest would be slower to adopt Covid-19 vaccines once eligible.

“When you look at this vaccination program for our littlest Americans, it will feel a little different than the vaccination programs we’ve run before. And that’s because we know parents will be turning to their pediatricians and their family physicians,” White House Covid-19 response coordinator Dr. Ashish Jha told reporters at the White House last month. “We have been guided in our approach by very clear data that says that most parents want to vaccinate their littlest ones in familiar settings. We also know that many parents have questions. And we want to encourage … every parent to talk to their physician, to talk to the pediatrician, to talk to the family physician. We also know that confidence in vaccines builds over time.”

Dr. Sean O’Leary, chair of the American Academy of Pediatrics Committee on Infectious Diseases, told CNN in an interview that it’s too early to judge the success of the rollout for the young age group.

“The campaign is still getting ramped up,” he said, adding that there is also “often a lag in data.”

O’Leary noted that many parents are taking a “wait-and-see” approach and echoed the White House’s assessment that many parents are making these decisions during routine visits with their child’s medical provider, suggesting that uptake will continue to increase. And, he added, many primary care providers aren’t yet stocking the specialized vaccines for children under 5, presenting additional challenges for distribution.