Ashton Kutcher Photo by: Dave Allocca / startraksIt may sound like an episode of Punk'd but this time it's real. Guests at Ashton Kutcher's 30th birthday party at the trendy New York bar Socialista are being urged to get a Hepatitis A vaccination because one of the bartenders was infected. Among the A-listers at the Feb. 7 event: Kutcher's wife Demi Moore, Madonna, Bruce Willis, Gwyneth Paltrow, and Salma Hayek. The bartender also worked on Feb. 8 and Feb. 11. "We are asking these bar patrons to get this vaccination as a precautionary measure," said Dr. Sharon Balter, medical epidemiologist at the New York City Department of Health and Mental Hygiene.