Three Republican candidates for president tackled the issue of childhood vaccines in Wednesday night's debate, saying they supported spacing vaccines over time instead of sticking to the current schedule.

But some experts say spacing vaccines leaves children vulnerable to diseases for longer periods of time.

"I am totally in favor of vaccines, but I want smaller doses over a longer period of time," said Donald Trump, who suggested that childhood vaccines may be responsible for autism.

"Just the other day, two years old, two and a half years old, a child, a beautiful child went to have the vaccine, and came back, and a week later got a tremendous fever, got very, very sick, now is autistic," Trump said.

But Ben Carson, a retired pediatric neurosurgeon, defended vaccines. "There have been numerous studies, and they have not demonstrated that there is any correlation between vaccinations and autism," he said.

He then agreed with Trump's position of spacing vaccines over a longer period of time.

"But it is true that we are probably giving way too many in too short period of time, and a lot of pediatricians now recognize that, and I think are cutting down on the number and the proximity in which those are done" Carson said.

Senator Rand Paul, an ophthalmologist, also agreed with spacing vaccines.

"I'm for vaccines, but I'm also for freedom," he said. "Even if the science doesn't say bunching them up is a problem, I ought to be able to spread my vaccines out a little bit at the very least."

However, some experts believe the current vaccine schedules shouldn't be altered.

Dr. Paul Offit, chief of the division of infectious diseases at the Children's Hospital of Philadelphia, told Live Science that evidence supports the current recommendations.

"To suggest that you make your own schedule is dangerous," he said. "That's why we saw the measles outbreak in Disneyland this year," he said, suggesting the outbreak was due to parents choosing to delay vaccinations."

Dr. William Schaffner, a professor of preventive medicine at Vanderbilt University, told Live Science that extending the current schedule leaves children susceptible to diseases, and that fear by some that the current schedule overwhelms an infant's immune system isn't accurate.

"That's been shown clearly not to be the case," he told Live Science. "It's safe and effective."

None of the presidential candidates mentioned the fact that last summer Dr. William Thompson, a senior epidemiologist at the Centers for Disease Control, admitted he had helped the CDC hide data from a study which linked the MMR vaccine to autism.