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.