Efron became a teen heartthrob with his starring role as Troy Bolton in the hit Disney Channel TV movie "High School Musical" and its sequel. He also starred in the film "Hairspray."
He was hospitalized a day after Walt Disney Studios Motion Picture Productions announced that he and his five "High School Musical" co-stars had signed on to appear in the theatrical film "High School Musical 3: Senior Year."
Efron, Vanessa Hudgens, Ashley Tisdale, Lucas Grabeel, Corbin Bleu and Monique Coleman will star as high-school seniors staging an elaborate musical before they graduate, the studio said.
Filming was scheduled to start in the spring, the studio said.
In August, 18.6 million viewers watched the first telecast of "High School Musical 2," Disney said.
The first film debuted in January 2006 and became an instant hit, mostly with teens and preteens.
The show's soundtracks, concert series, ice skating tour and Broadway-style show have also been successful.
