Actress Jessica Biel generated controversy last week when she lobbied, along with anti-vaccine activist Robert F. Kennedy Jr., against a California bill that would make it more difficult to obtain medical exemptions to vaccines.

Biel is the latest example of a celebrity to become a de facto spokesperson for the anti-vaccine movement, at a time when a failure to immunize children is driving the biggest measles outbreak in decades.

Joining Boston Public Radio to weigh in on this topic and more was medical ethicist Arthur Caplan. Caplan is the Drs. William F. and Virginia Connolly Mitty Chair and director of the Division of Medical Ethics at NYU's Langone Medical Center. He is also the co-host of the "Everyday Ethics" podcast.

Caplan believes the media attention garnered by celebrities with opinions not based on scientific consensus is a dangerous tool in the anti-vaccine movement's arsenal.

"Every nudnik celebrity — recently, Jessica Biel — who announces they don't like vaccines gets massive coverage," Caplan said. "In general, the best tool the anti-vaxxers have is to pull the celebrity card, and that really pulls attention."