Colorado’s rate of vaccination against measles is at 86 percent -- about even with other states, according to the Centers for Disease Control and Prevention. A survey of the state's kindergartners has it a few points lower.

Whatever the exact number, Colorado is working to reach the 90 percent range. That’s the target health professionals say is needed to head off a potential measles outbreak, according to said Dr. Rachel Herlihy of the state health department’s Division of Disease Control.

"We certainly know that not enough of our children are protected against Measles," she said.

Under current law, Colorado parents may exempt their children from school-required vaccinations for personal beliefs by providing only their signature. 

"Even if we did have a high overall state coverage rate for Measles, we do still know that we would have pockets or communities or individual schools or play groups that are very vulnerable to cases of Measles," she said. 

So far, Colorado has seen only one case of measles this year. That happened in January, stemming from the outbreak at Disneyland in California.

The most important tool to preventing an outbreak is to ensure high rates of vaccination in the state, Herlihy said. And it's never too late for children and adults who haven't been vaccinated against Measles to get the shot.

In 2013, 538 Colorado children were hospitalized with vaccine-preventable diseases, according to the Colorado Children's Immunization Coalition. It cost $29.2 million to treating children in Colorado for vaccine-preventable diseases in the same year, they say.