In tweet, Hillary Clinton encourages vaccinations

Former Secretary of State Hillary Clinton shared her views on inoculations Monday night, tweeting a disagreement with potential 2016 Republican presidential candidates' questioning of mandatory vaccinations.

The tweet comes after New Jersey Governor Chris Christie and Kentucky Rand Paul split with conventional thinking on vaccinating children against diseases.

"It's much more important, I think, what you think as a parent than what you think as a public official," Christie said while traveling in London Monday. "But I also understand that parents need to have some measure of choice in things as well so that's the balance that the government has to decide."

Christie differed from President Obama, who said in an interview with NBC on Sunday to parents: "You should get your kids vaccinated."

"It's good for them, and the challenge you have is if you have a certain group of kids who don't get vaccinated, and if it grows large enough that a percentage of the population doesn't get vaccinated and they're the folks who can't get vaccinated, small infants, for example, or people with certain vulnerabilities that can't vaccinated, they suddenly become much more vulnerable," he said.

Paul, who is a physician himself, said Monday that he believes vaccinations should be voluntary.

"I think there are times in which there can be some rules but for the most part it ought to be voluntary," Paul told conservative radio host Laura Ingram on her show Monday.

A measles outbreak has recently placed the disease, which had been all but eradicated at the forefront of a debate on the topic of vaccinations.

Tom Frieden, the director of the Centers for Disease Control and Prevention (CDC), said his agency is "very concerned" about the possibility of a large measles outbreak in the U.S. because of the growing number of people who have not been vaccinated against the disease.

"What we've seen is, as over the last few years, a small but growing number of people have not been vaccinated. That number is building up among young adults in society, and that makes us vulnerable," Frieden said in an interview on CBS' "Face the Nation" Sunday.

There are at least 102 reported cases of measles in 14 states, according to CDC statistics. Frieden said there will likely be more cases going forward, and the CDC is taking "aggressive public health action" to identify contacts and isolate those infected in order to stop the spread.