Measles Outbreak Proves Delicate Issue to G.O.P. Field

An outbreak of measles that started at Disneyland has turned a spotlight on those who choose not to vaccinate their children. How did we get to a point where personal beliefs can triumph over science?

WASHINGTON — The politics of medicine, morality and free will have collided in an emotional debate over vaccines and the government’s place in requiring them, posing a challenge for Republicans who find themselves in the familiar but uncomfortable position of reconciling modern science with the skepticism of their core conservative voters.

As the latest measles outbreak raises alarm, and parents who have decided not to vaccinate their children face growing pressure to do so, the national debate is forcing the Republican Party’s 2016 presidential hopefuls to confront questions about whether it is in the public’s interest to allow parents to decide for themselves.

Gov. Chris Christie’s trade mission to London was suddenly overshadowed on Monday after he was quoted as saying that parents “need to have some measure of choice” about vaccinating their children against measles. The New Jersey governor, who is trying to establish his credibility among conservatives as he weighs a run for the Republican nomination in 2016, later tried to temper his response. His office released a statement clarifying that “with a disease like measles there is no question kids should be vaccinated.”

An earlier version also misattributed a quote. It was Dr. Thomas Frieden, director of the Centers for Disease Control, who said on the ABC News program “This Week” that the science was clear and convincing. “Study after study has shown that there are no negative long-term consequences. And the more kids who are not vaccinated, the more they’re at risk and the more they put their neighbors’ kids at risk as well.” It was not Gov. Scott Walker of Wisconsin, a possible 2016 presidential candidate who also appeared on the show.

Also, because of an editing error, a previous version of the article misstated the TV show on which Mr. Obama was appearing when he urged parents to “get your kids vaccinated.” It was the “Today Show,” not “Meet the Press.”

Jeremy W. Peters reported from Washington, and Richard Pérez-Peña from New York. Nick Corasaniti contributed reporting from Washington, and Kitty Bennett from St. Petersburg, Fla.

A version of this article appears in print on February 3, 2015, on page A1 of the New York edition with the headline: Measles Proves Delicate Issue to G.O.P. Field. Order Reprints| Today’s Paper|Subscribe

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