LAUREN HUTTON has a space between her fangs as the vapid vampiress of "Once Bitten," a sappy, sophomoric sex farce in which the supernatural's answer to Mrs. Robinson sucks the blood of virgin boys.

Well-preserved for a 400-year-old who never gets any sun, the aging fiend must nonetheless feed from the thigh of a virgin teen to retain youth, beauty and that Cover Girl look. But life in the fast vein isn't what it was in the Dark Ages (or even the '50s), when uninitiated males did not have access to MTV -- thus there was still a chance they'd remain chaste till the wedding night.

Is virtue lost? wonders the vampiress, pedaling furiously on her exer-cycle, maintaining aerobic fitness even while undead. Her gay valet -- a tiresome role for Cleavon Little -- consoles her with a tumbler of blood garnished with a celery stick. She moues thoughtfully.

"I came out of the closet centuries ago," he minces, uttering one of the movie's many dated inanities. (The writers still think "What's your sign?" is a good joke.)

Meanwhile, three restive adolescents drive into L.A. from the suburbs, where the virgins are. Comedic actor Jim Carrey debuts as a fresh-scrubbed high school heartthrob who's saving himself for his twerpy best girl (Karen Kopkins), with Thomas Ballatore and Skip Lackey as inept, horny sidekicks.

Once bitten by the vampire, Carrey is transformed. He sleeps in a footlocker, drinks hamburger blood and mousses his hair back. Ooo, scary.

His girlfriend visits a librarian and correctly deduces that her boyfriend has probably been bitten by a vampire. At the girl's request, his friends try to learn whether there are two sores on the inside of his thigh. At times, the scenario rivals an armed-forces VD movie.

Hutton, whose emotive range is second only to Ali McGraw's, is hardly an 18-year-old's dream come true. Her "big luscious magoombahs," as they are affectionately called, are hardly magoombah-like. Hutton and Kopkins, also a real-life model, finally square off in the high school gymnasium during the Halloween hop -- Hutton in a pair of black tights and a tuxedo jacket, Kopkins in a white slip -- where they dance at each other, apparently acting out a classic clash between good and evil.

"He doesn't want you cause you're mean and evil," says Kopkins. "He wants me because I'm sweet and pure."

Plus she's thinking of becoming a vegetarian, no doubt.

The whole thing kind of makes you long for "Porky's IV."