The Brotherhood (2001)

In high school, Christopher 'Chris' Chandler was almost too good to be true: his gorgeous, perfectly trained body earned him a place in the Allstate swim-team and his scholarship for the small US college Drake, yet he never fell for pride or the temptation of parties and groupies, remaining modest and considerate. As a freshman, he takes his nerdy roomy Dan under his wing and even grants his request to go to a frat party (just the sort of elitist arrogance Chris loathes), where they got invited by Megan, a hip girl student Dan wouldn't dare to dream about. Alas the invitation was really arranged by Devon Eisley, the president of the somewhat Gothic fraternity "Doma (House of) Tau Omega", who has found a key to eternal youth without having to become blood-drinking vampires and tricks Chris at the party into drinking each-others blood, after which he starts changing for the worse...