Car seat? Check. Sunscreen? Got it. First-aid kit? Roger that. When it comes to taking kids on vacation, parents are all about safety. So in light of the recent measles outbreak, should some families be weighing a destination’s vaccination rate when deciding where to go — and where to avoid?

More than 100 cases of measles have been reported in 14 states since the current outbreak originated at Disneyland in December. It highlights just how quickly measles can spread when unvaccinated tourists pick up the virus and then bring it back to their home communities, said Dr. William Schaffner, professor of preventive medicine and infectious diseases at the Vanderbilt University School of Medicine.

“I think the Disneyland outbreak clearly has brought this issue to everyone’s forceful attention, and it’s got to be recognized how fragile was our triumph in eliminating measles from the United States, which we had been successful at doing,” Schaffner said.

According to the Centers for Disease Control, the U.S. saw roughly 60 cases of measles each year between 2001 and 2010. But last year there were 20 outbreaks and 644 reported cases — the most in two decades. Now, less than six weeks into 2015, we’ve already had more cases than are typically diagnosed in a year.

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Public health officials say a small but growing group of families are deciding not to vaccinate their children, which is compromising the “herd effect” of protection achieved when over 95 percent of the population is vaccinated. This heightens the risk for people who are not eligible for certain vaccines — babies under a year old, pregnant women and people with compromised immune systems.

“With any vaccine-preventable disease, the principles are the same. In any country with low vaccination rates, you are going to see the likelihood of an outbreak,” said Dr. Gary Brunette, the CDC’s branch chief of travelers' health. “And you’ll see that not only with measles but all the vaccine-preventable diseases, such as mumps, rubella and varicella [chicken pox].”

Of those, measles is by far the most worrisome. “Measles kills, and it’s also the easiest to catch. It’s the single most transmissible virus we know, and that accounts for the fact that it’s spreading so rapidly among these kids,” Schaffner said.

One in 12 children in the U.S. is not receiving the first dose of the measles vaccine on schedule, and there are now 17 states where more than 10 percent are not getting at least one dose, according a telebriefing by the CDC last month.

Babies typically receive their first dose of the MMR (measles, mumps, rubella) vaccine at 1 year old. For families traveling out of the country, the CDC recommends vaccinating babies over 6 months old.  

But what about domestic travel? “We would recommend parents talk to their physicians and that children be up to date for their age, but there are no further recommendations for travel,” said Shannon Stokley, associate director for science at the CDC’s Immunization Services Division. “At the end of the day, the point is to get everyone in the family vaccinated. That’s your best protection.”

“We see variations by state, but nationally vaccination coverage has been over 90 percent for quite some time for infants 19 to 35 months of age, and that has remained consistently high over the years,” Stokley said.

But the national vaccination rate can be misleading, Schaffner said. Some states, such as Colorado and Pennsylvania, have vaccination rates lower than that of France, where measles still circulates. “And interestingly, it’s Mississippi, last in so many things, that is first in immunization rates, because that state does not allow either personal belief or religious exemptions,” said Schaffner. As a result, Mississippi has not had a reported case of the measles in over 20 years.

So how likely is it that an unvaccinated child will contract the measles while on vacation in the United States?

“If you had asked me this question five or six years ago, I would have said that the risk was virtually nonexistent,” said Schaffner. “Over the past several years, with more and more children being withheld from vaccinations and more and more introduction of measles, I would have said it’s still very low. But today, in the context of the Disneyland outbreak, with it having spread to so many states, I would still acknowledge that the risk is low but it’s much larger than it was, and I would be nervous about that.

“Parents of unvaccinated infants may want to sit down with their pediatrician and assess the risk. We might think about this as though we would international travel,” said Schaffner. “If a family is sufficiently concerned about this, a pediatrician could offer this same sort of strategy to provide at least some protection to an infant analogous to what the pediatrician would recommend were the child to be traveling outside the United States to an area where there was measles. I think that’s perfectly reasonable.

“An unvaccinated child will be exposed to risk everywhere, but more so in certain circumstances than in others," said Schaffner. "For example, more so in Colorado than in Mississippi. But I don’t think you’re going to get a recommendation with a capital R from the CDC or the CDC’s Advisory Committee on Immunization Practices.”

Suzanne Rowan Kelleher is the family vacations expert at About.com.