New Jersey Gov. Chris Christie, a likely Republican candidate for president, said Monday that parents should have some choice on whether to vaccinate their children.

Christie's comments, made after a tour of a biomedical research center during a three-day trade mission to the United Kingdom, come as a measles outbreak centered in California has sickened more than 100 people in the U.S.

Christie said that he and his wife had vaccinated their children, describing that decision as "the best expression I can give you of my opinion." He said they believe doing so is an "important part of making sure we protect their health and the public health."

"But," Christie added, "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."

A few hours after Christie spoke, his office said in a statement that the governor "believes vaccines are an important public health protection and with a disease like measles there is no question kids should be vaccinated."

All states now require children to get certain vaccinations to enroll in school, although California and New Jersey are among 20 states that let parents opt out by obtaining personal belief waivers. Parents in New Jersey seeking a medical exemption have to submit a written statement from their doctor or registered nurse indicating why the exemption is needed.

Some people worry that vaccines can cause developmental problems in children, despite scientific evidence disproving any link. Others object for religious or philosophical reasons. The New Jersey health department's guidelines on vaccines say that objections "based on grounds which are not medical or religious in nature and which are of a philosophical, moral, secular, or more general nature continue to be unacceptable."

Christie's comments stand in contrast to those of President Obama, who said in an interview with NBC News that all parents should get their kids vaccinated. Those children who are not, he said, put infants and those who can't get vaccinations at risk.

"I understand that there are families that, in some cases, are concerned about the effect of vaccinations," Obama said. "The science is, you know, pretty indisputable."

The measles-mumps-rubella vaccine, commonly called the MMR, is 97 percent effective at preventing measles, according to the Centers for Disease Control and Prevention. New Jersey requires MMR vaccines for children between 12 and 15 months, and then a second at between 4 and 6 years.

Measles is a highly contagious disease that spreads through the air, with symptoms that include fever, runny nose and a blotchy rash. The current outbreak originated at Disney theme parks last month, and Mexico and at least six other U.S. states have recorded measles cases connected to Disneyland.

When asked by reporters in Cambridge, after touring the facilities of MedImmune, the manufacturer of the flu vaccine FluMist, if leaving parents with the option to pass on vaccinations for their children is dangerous, Christie said there "has to be a balance."

"It depends on what the vaccine is, what the disease type is and all the rest," he said. "And so I didn't say I'm leaving people the option. What I'm saying is that you have to have that balance in considering parental concerns."

Christie said the conversation about whether to vaccinate needs to include the type of disease at issue. He said "not every vaccine is created equal. And not every disease type is as great a public health threat as others."

The American Academy of Pediatrics urges parents to get their children vaccinated against measles and other childhood diseases. It says doctors should bring up the importance of vaccinations during visits if parents are reluctant, but should respect a parent's wishes unless there's a significant risk to the child.

"In general, pediatricians should avoid discharging patients from their practices solely because a parent refuses to immunize his or her child," according to guidelines issued by the group.