The vaccine designed by Pfizer and German partner BioNTech is now available for teenagers aged 12 and over.
For younger school-age children, Pfizer tested a much lower dose, one-third the amount of each injection currently given.
However, after the second dose, children ages 5 to 11 developed levels of antibodies to the coronavirus as strong as adolescents and young adults, Pfizer vice president Bill Gruber told the Associated Press (AP).
“I think we really hit the sweet spot,” said Gruber, who is also a pediatrician.
The same official said that the companies intend to submit to the Food and Drug Administration (FDA), by the end of the month, the request for emergency use of the vaccine in that age group, followed soon after by requests in the same direction with European regulators and in the United Kingdom.
Many Western countries have so far not vaccinated children before the age of 12, waiting for evidence of what the right dose will be and that it will work safely in smaller portions.
But last week, Cuba began immunising 2-year-olds with its vaccines, and the Chinese regulator authorised two of its brands for children under 2 years old.