SAN DIEGO — A growing number of U.S. public schools are using mascots, food trucks and prize giveaways to encourage students to get vaccinated before summer vacation.

The massive effort to create a pep-rally atmosphere comes only weeks after the Pfizer coronavirus vaccine was approved for younger adolescents ages 12 to 15. Administrators want to get as many shots in students’ arms as possible and hope it will pave the way to return to regular classes in the fall.

So far, about 14% of the nation’s 15 million kids ages 12 to 15 have received their first shot, according to the Centers for Disease Control and Prevention. Among 7.5 million teens ages 16 to 17, that number goes up to 34%, and about 22% have had both shots, according to the latest figures released Monday. The doses are scheduled about three weeks apart.