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Colorado kindergartners have the lowest vaccination rate for measles in the country, a distinction that health experts say makes the state especially vulnerable to a major outbreak.

Although only one Coloradan has had a confirmed case of the illness since an outbreak started at Disneyland, in California, the low vaccination rate here is a big concern — and a source of bewilderment.

“We are going to have a large outbreak of measles,” said Dr. Edwin J. Asturias, a pediatrician with the Colorado School of Public Health, University of Colorado School of Medicine and Children’s Hospital Colorado.

“For almost a decade we have been accumulating people without protection,” said Asturias, an expert in infectious diseases and vaccines. “We are like a forest waiting to catch fire.”

One reason Colorado has such a low vaccination rate is that it has a high exemption rate. The state is one of 20 that allow parents to claim any kind of personal opposition to immunization programs, and there’s a strong sentiment among some parents here that they should be able to choose.

“It’s a parent’s right to decide what medical procedure and products are used on their children,” said Theresa Wrangham of Louisville, executive director of the nonprofit National Vaccine Information Center. “If people want to use vaccines, they should have access to them. Vaccines should be safe as possible, but they are not totally 100 percent safe.”

Among the 49 states and the District of Columbia reporting vaccination coverage for measles, mumps and rubella, or MMR, for the 2013-14 school year, Colorado stood dead last, according to the Centers for Disease Control and Prevention. Data wasn’t available for Wyoming.

National median vaccination coverage was almost 95 percent for two doses of MMR vaccine during the past school year, according to CDC estimates based on school records. In Colorado, less than 82 percent of kindergartners are fully vaccinated.

When the vaccinated population falls below 95 percent, Asturias said, it loses its herd immunity — enough vaccine coverage so that it’s unlikely a susceptible person will come into contact with an infectious person. The 95 percent who are fully immune act like a firewall in the spread of the highly contagious disease.

Fight intensifying

The fight over vaccinations is intensifying as measles makes a big comeback, according to federal public health officials. In the first month of this year, 102 people from 14 states were reported to have measles, including one reported case in El Paso County.

Most of these cases were part of a large, ongoing outbreak linked to Disneyland, according to the CDC. But this year’s outbreak follows a record number of reported cases in 2014: 644 in 27 states. That was the greatest number of cases since measles was pronounced “eliminated” from the United States in 2000, the CDC says.

Niki Tracy of Salida was one of those who resisted having her child vaccinated for MMR, until the recent measles outbreak forced her to reconsider. She took her 2½-year-old daughter, Rilynn, in for the shot Friday.

Rilynn battles a paralyzing condition known as transverse myelitis.

She came down with TM in 2013, two weeks after receiving a Prevnar vaccination, given to prevent pneumococcal disease, a serious infection caused by a bacteria. Tracy believes the vaccine brought on her daughter’s TM.

She also, however, believes in the need to protect her daughter against other possible diseases through vaccination.

“Originally, when this all started, we were told to stay away from vaccines. Now, research says, get them back on a vaccination schedule, a more conservative vaccination schedule,” Tracy said.

After lots of questions, research and soul searching, Tracy says she’s comfortable scheduling Rilynn for future vaccines — just one at a time, no multiple-shot sessions.

“For us, part of the reality check we had to have was: If we spent our entire lives trying to protect Rilynn from TM, we open ourselves up for all sorts of other things,” Tracy said. “It was the toughest decision we’ve had to make.”

After a long hospital stay, a variety of medical treatments, and continued physical therapy, Rilynn’s condition, motor control and mobility are improving.

Vaccine researcher Jason Glanz, an epidemiologist with the Kaiser Permanente Institute for Health Research, sees the threshold level for a measles outbreak at vaccination coverage of 90 percent or less.

“We’re at a critical point now,” he said. “We’re always at risk for outbreaks when we dip below that level.”

The CDC recommends that all children get two doses of MMR vaccine, with the first at 12-15 months of age and the second at 4-6 years. A second dose can be received sooner, as long as it is at least 28 days after the first dose.

One dose of measles vaccine is about 93 percent effective at preventing measles if one is exposed to the virus. Two doses increase effectiveness to about 97 percent, according to the state Department of Public Health and Environment.

To those parents who think it makes better sense to let their children naturally acquire immunity through exposure to disease, Asturias says parents have the right to ask questions.

“But they need to educate themselves better,” Asturias said. “Some of the children will get very sick. Do you really want to gamble with your children’s health?”

Don’t demonize parents

Glanz said it’s important not to demonize parents who want to delay or refuse vaccination of their children.

“It is a lot of shots for children to get at once,” Glanz said. “It is traumatic for children. It was hard for me when I took my children … even with my head swimming in this data.”

These anti-vaccine parents’ decisions aren’t irrational, he said, but such choices are based on faulty information.

“In the case of vaccinations, there is only one good choice — to get the shots and get them on time,” Glanz said.

“You can’t ignore being dead last to get your kindergartners vaccinated. We’re winding the clock back to 1950,” said Rep. Dan Pabon, D-Denver, who is gathering information on measles and vaccines in advance of possibly drafting legislation to make it harder for parents to opt out.

“There’s literally a battleground in our classrooms,” with parents having to choose between their children’s health and their educations, Pabon said.

“When do we call this a health-care crisis?” he asked. “Do we wait until it’s a four-alarm fire?”

Tracy and Wrangham said parents who choose not to use vaccines are often ostracized.

Current public discourse over immunizations has reached a cacophony, Wrangham said, and those who decide not immunize are being threatened.

“What we are talking about is a very small minority of people who are delaying or not having vaccines,” she said, “but it’s a very hostile environment.”

Electa Draper: 303-954-1276, edraper@denverpost.com or twitter.com/electadraper