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© Stefani Reynolds/The New York Times via AP
Dr. Tony Fauci
Director of the National Institute of Allergy and Infectious Diseases Anthony Fauci said Thursday that though he "can't guarantee it," babies and toddlers aged 6 months to 5 years could be eligible for COVID-19 vaccination by spring.

"Hopefully within a reasonably short period of time, likely the beginning of next year in 2022, in the first quarter of 2022, it will be available to them," Fauci told Insider in an interview, though he cautioned that he was speculating, adding, "you've got to do the clinical trial."

Pfizer-BioNTech previously stated that results from their clinical trial in children in the age ranges of 2 to 5 years and 6 months to 2 years are expected as soon as the fourth quarter of this year.

According to a report by ABC Tampa in late October, Pfizer expects to apply this month for approval for its COVID-19 vaccine in children ages 6 months to 5 years, the last age range in the U.S. not yet being vaccinated.

"The Food and Drug Administration and CDC won't approve the vaccine until there's some data showing safety and efficacy," Philip Landrigan, a pediatrician and immunologist at Boston College, told CNN Health earlier this month.

"There's every reason to think that it will be safe, and it will be efficacious," Landrigan added. "But the agencies need to be cautious, justifiably so, and so they're not going to give the approval until they have the data."

According to CNN, Pfizer is the furthest along in trials for those aged 6 months to 5 years, but Moderna is also conducting studies in very young children.

"We don't have enough data now to present it for a regulatory approach, but right now, the data are being collected and analyzed," Fauci said when speaking to CNN earlier this month. "So we will be able to answer the question, I believe, within a reasonable period of time regarding the safety and the immunogenicity among those lower than 5 years old." According to CNN, Johnson & Johnson is currently in the first phase three study in adolescents ages 12 to 17 years old and expect results in the coming months. The White House announced Wednesday that 10 percent of children ages 5 to 11 have received their first coronavirus shot, following the approval of the Pfizer pediatric dose.