Kid-size doses of Pfizer’s COVID-19 vaccine appear safe and nearly 91% effective at preventing symptomatic infections in 5- to 11-year-olds, according to study details released Friday as the U.S. considers opening vaccinations to that age group.

The shots could begin in early November, with the first children in line fully protected by Christmas, if regulators give the go-ahead. That would represent a major expansion of the nation’s vaccine drive, encompassing roughly 28 million elementary school-age youngsters.

Details of Pfizer’s study were posted online. The Food and Drug Administration was expected to post its own review of the company’s safety and effectiveness data later in the day.

Advisers to the FDA will publicly debate the evidence next week. If the agency itself authorizes the shots, the Centers for Disease Control and Prevention will make the final decision on who should receive them.

Full-strength Pfizer shots already are authorized for anyone 12 or older, but pediatricians and many parents are anxiously awaiting protection for younger children to stem rising infections and record hospitalizations among them from the extra-contagious delta variant and to help keep kids in school.

The Pfizer study tracked 2,268 children in the 5-to-11 group who got two shots three weeks apart of either a placebo or the low-dose vaccine.

Researchers calculated the low-dose vaccine was nearly 91% effective, based on 16 COVID-19 cases in youngsters given dummy shots versus three cases among vaccinated children. There were no severe illnesses reported among any of the youngsters.