WASHINGTON — The U.S. Food and Drug Administration is expected to authorize Pfizer’s COVID-19 vaccine for youngsters ages 12 to 15 by next week, according to a federal official and a person familiar with the process, setting up shots for many before the beginning of the next school year.

The announcement is set to come a month after the company found that its shot, which is already authorized for those age 16 and older, also provided protection for the younger group.