Parents should be the ones to decide whether they vaccinate their children, not the government, Sen. Rand Paul argued in a contentious interview on Monday, just hours after President Barack Obama and likely 2016 rival Chris Christie made controversial comments on the subject.

Paul, a former ophthalmologist, has heard of cases where vaccines lead to "mental disorders," On Politics reported. Earlier in the day, the likely Republican presidential candidate told conservative radio host Laura Ingraham that most vaccines "ought to be voluntary."

"I've heard of many tragic cases of walking, talking normal children who wound up with profound mental disorders after vaccines," the Kentucky Republican said in an interview with CNBC anchor Kelly Evans. "There are times when there can be rules. But for the most part it ought to be voluntary."

"I'm not arguing vaccines are a bad idea. I think they're a good thing, but I think the parents should have some input," he added. "The state doesn't own your children. Parents own the children and it is an issue of freedom."

"I think vaccines are one of the greatest medical breakthroughs that we have," he said. "But you know, for most of our history, they have been voluntary. So I don't think I'm arguing for anything out of the ordinary."

Citing a personal experience where doctors wanted to immunize his children against hepatitis B after they were born, Paul said he "didn't like them getting 10 vaccinations at once" and staggered the vaccinations over time, ABC News reported.

Over the weekend, Obama urged Americans to vaccinate their children amid a measles outbreak that originated at Disney theme parks during the holidays. "You should get your kids vaccinated," the president said in an interview with NBC on Sunday.

However New Jersey Gov. Christie opposed the president's view on Monday, stating that families should have a "measure of choice" in whether they should vaccinate their children.

"There has to be a balance and it depends on what the vaccine is, what the disease type is, and all the rest," Christie said, according to the Washington Post. "Not every vaccine is created equal and not every disease type is as great a public health threat as others."

But after receiving wide criticism for his comments, the governor's office issued a statement stressing that "there is no question kids should be vaccinated" against measles.

"Republican after Republican is bowing to the rhetoric of the anti-vaccination movement instead of standing up for the science supported by almost all doctors and scientists on protecting our kids and keeping our nation safe," the Democratic National Committee said.

Meanwhile the importance of vaccines along with their relatively low risk of harm was affirmed by the American Academy of Pediatrics on Monday.

The group stressed that the MMR vaccine for measles, mumps and rubella is one of the safest and most effective vaccines given, and strongly urged parents to stick to the vaccine schedule recommended by the U.S. Centers for Disease Control and Prevention.