Kentucky Sen. Rand Paul (R) is an ophthalmologist by training. (Photo by Michael S. Williamson/The Washington Post)

This post has been updated.

Kentucky Sen. Rand Paul (R), a likely 2016 presidential candidate and a certified physician, weighed in on the vaccination debate Monday by asserting that he believes most vaccines should be voluntary.

"I'm not anti-vaccine at all but...most of them ought to be voluntary,” Paul told Laura Ingraham on her radio show Monday. "I think there are times in which there can be some rules but for the most part it ought to be voluntary.”

Paul’s comments follow a minor controversy Monday stirred by remarks by New Jersey Gov. Chris Christie (R)—another potential 2016 candidate—in which he called for “balance” in vaccination requirements in order to allow for parental discretion. The Republican governor walked back his comments several hours later.

"The Governor believes vaccines are an important public health protection and with a disease like measles there is no question kids should be vaccinated," Christie's office said in a statement.

[RELATED: Christie clarifies comments on measles vaccine]

A nationwide measles outbreak has transformed mandatory vaccination practices into a potent political issue. Medical professionals attribute the outbreak to increasing vaccination skepticism and have urged parents to vaccinate their children. On Sunday, President Obama weighed in, saying "there is every reason to get vaccinated — there aren’t reasons to not."

Paul's comments were distributed online by the Democratic National Committee Monday.

Paul pointed to a 2007 effort by then-Texas Gov. Rick Perry (R), who is also considering a 2016 run for the Republican nomination, that would have required young girls to receive a vaccine for human papillomavirus (HPV). That move was sharply attacked by social conservatives who said requiring vaccination against HPV, which is a sexually transmitted disease, would encourage promiscuity. The Texas legislature eventually overturned the mandate. Perry later called the order “a mistake.”

“While I think it’s a good idea to take the vaccine, I think that’s a personal decision for individual’s to take,” Paul said, attempting to strike a balance between responsible medical protocols and personal choice.

Paul went on to mention that he was frustrated when doctors suggested his son be vaccinated for Hepatitis B, which he said made him uncomfortable as a parent.

“I didn’t like them getting 10 vaccines at once so I actually delayed my kids’ vaccines and had them staggered over time,” he said.

Speaking on CNBC's "Closing Bell" later Monday, Paul said that there should be increased public awareness that vaccines are good for children, but reiterated that vaccines should be voluntary, as he said they were in the past. He said that he has heard stories of children who developed "profound mental disorders" after being vaccinated. Paul did not say which vaccines those children had received.

"I’ve heard of many tragic cases of walking, talking normal children who wound up with profound mental disorders after vaccines," Paul said. "I’m not arguing vaccines are a bad idea. I think they’re a good thing. But I think parents should have some input. The state doesn’t own your children, parents own the children and it is an issue of freedom and public health."

A link between vaccinations and autism was alleged in a 1998 study that the medical and scientific communities have now widely discredited. The journal that published the study retracted it and the author lost his medical license.

[RELATED: More than 100 confirmed cases of measles in the U.S., CDC says]