CAMBRIDGE (CBS/CNN) – Moderna’s CEO said its COVID-19 vaccine will likely be available to children as young as five by the early fall.

“I think it’s going to be early fall, just because we have to go down in age very slowly and carefully,” the Cambridge-based company’s CEO Stéphane Bancel said Monday at an event hosted on the social media platform Clubhouse.

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Pfizer’s vaccine has already been approved for emergency use by the FDA for children as young as 12. The company announced Tuesday it’s beginning the next phase of studying its vaccine safety on kids ages 5 to 11. Moderna said it is testing its vaccine on children as young as six months.

Bancel noted the process will take time as it determines the appropriate dosages for small children.

“We anticipate data available in the September/October time frame,” he said.

His comments came as research in the journal JAMA Network Open showed that children with underlying health conditions are more likely to be hospitalized or get seriously ill from COVID-19.

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The data from 43,465 COVID-19 patients ages 18 years and younger who visited an emergency department or were hospitalized showed those with underlying health conditions were more likely to experience severe illness or hospitalization, with about 28.7% of all those patients having underlying health conditions.

Among the 4,302 who were hospitalized, more than 2,700, 62.9%, had underlying health conditions, researchers noted.

Patients with Type 1 diabetes and obesity were the most likely to be hospitalized, while those who were born prematurely were more likely to experience severe illness from COVID-19, the data showed.

The report suggested that this information be considered as vaccination priorities and regulations are created.

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(© Copyright 2021 CBS Broadcasting Inc. All Rights Reserved. CNN’s Hollie Silverman contributed to this report.)