U.S. regulators on Monday expanded the use of Pfizer’s vaccine for the coronavirus disease 2019 (Covid-19) to children as young as 12, offering a way to protect the nation’s adolescents before they head back to school in the fall and paving the way for them to return to more normal activities.

Shots could begin as soon as Thursday, after a federal vaccine advisory committee issues recommendations for using the two-dose vaccine in 12- to 15-year-olds. An announcement is expected Wednesday.

Most Covid-19 vaccines worldwide have been authorized for adults. Pfizer’s vaccine is being used in multiple countries for teens as young as 16, and Canada recently became the first to expand use to 12 and up. Parents, school administrators and public health officials elsewhere have eagerly awaited approval for the shot to be made available to more kids.

“This is a watershed moment in our ability to fight back the Covid-19 pandemic,” Dr. Bill Gruber, a Pfizer senior vice president who’s also a pediatrician, said.

The Food and Drug Administration declared that the Pfizer vaccine is safe and offers strong protection for younger teens based on testing of more than 2,000 U.S. volunteers ages 12 to 15. The agency noted there were no cases of Covid-19 among fully vaccinated adolescents compared with 16 among kids given dummy shots. More intriguing, researchers found the kids developed higher levels of virus-fighting antibodies than earlier studies measured in young adults.