About 900,000 U.S. children aged 5 to 11 years received their initial dose of the Pfizer COVID-19 vaccine during the first week of eligibility for that age group, the Biden administration said Wednesday. Not only that, nearly 700,000 more are scheduled in the coming days, health officials added.

The low-dose Pfizer vaccine for younger children was approved on Nov. 2, and the first doses were administered in some locations the next day, according to the Associated Press. Nearly 20,000 pharmacies, clinics, and doctors' offices are giving the shots to children aged 5 to 11 years. About 28 million youngsters in that age group are eligible for the vaccine. Children who get their first of two shots by the end of next week will be fully vaccinated by Christmas.

Still, some experts say that demand could begin to recede in only a matter of weeks. They pointed to polling data that suggests only a fraction of parents plan to get their children shots immediately, and they suspect the trend will mirror what happened when children aged 12 to 15 years were first authorized to get COVID-19 shots back in May, the AP reported.

In the first week after vaccines for 12- to 15-year-olds were approved, the number of adolescents getting a first shot jumped by roughly 900,000, according to an American Academy of Pediatrics analysis of federal data. The next week, it rose even further, to 1.6 million, the AP said. Since then, adolescent vaccinations have dropped considerably, to just 32,000 getting their first shots last week. Only about half of adolescents aged 12 to 17 years are fully vaccinated compared with 70 percent of adults.

"There was an initial burst," said Shannon Stokley, M.P.H., of the U.S. Centers for Disease Control and Prevention. But the number dropped steadily for months, interrupted only briefly in early August as the delta variant surged and parents were sending their children back to classrooms, the AP reported. "We're going to have a lot of work to do to communicate to parents about why it's important to get children vaccinated," Stokley added.