Is Indiana's vaccination rate high enough to keep out measles?

Fifteen years ago, the Centers for Disease Control and Prevention declared measles eliminated from the United States. That proclamation turns out to have been more than a bit optimistic.

Technically, the statement still holds, as health officials consider measles to be gone from a country when the disease is not being continuously transmitted throughout the year.

But as recent weeks have shown, measles is far from eliminated in this country. More than 90 people from 11 states have developed measles in the first three weeks of the year, the great majority of them infected during an outbreak that started at Disneyland in December.

Last year saw the highest number of measles cases since 2004, 644 in 27 states, according to the CDC.

Indiana has seen no cases of measles this year.

Whether the state stays measles-free, however, is largely a matter of luck, state health officials say.

"We are concerned," said Dr. Joan Duwve, chief medical consultant with the Indiana State Department of Health. "Only one case of measles constitutes an outbreak for that disease here in the state of Indiana."

And once there's one case of measles, others may follow — especially among the unvaccinated.

The measles virus is incredibly hardy, is airborne and can be passed on before an infected person becomes symptomatic. If an infected person is in a room with 100 unvaccinated people, 90 of them will become ill, Duwve said.

Indiana may enjoy more protection than other states, experts say.

For better or worse, Indiana does not have an international destination akin to Disneyland, which draws thousands of people each day, some from countries with lower vaccination rates.

Perhaps even more important, there are fewer unvaccinated children than in states such as California, Colorado and Arizona, which have had cases related to the Disneyland outbreak.

In California, more than 3 percent of all kindergarten students had exemptions, compared with about 1 percent in Indiana.

About 0.81 percent, or 493, of all Indiana sixth-graders and 0.74 percent, or 456, of all kindergartners had a religious exemption in the 2013-14 school year, according to state statistics. That same year 4,455 kindergarten students did not have the MMR vaccine, which includes protection against measles, meaning only 92.7 percent of the grade was fully vaccinated.

Indiana's policies have helped keep the unvaccinated rates here relatively low, said Ross Silverman, a professor of health policy and management at the Indiana University Richard M. Fairbanks School of Public Health at IUPUI. Silverman recently published an article in the Journal of the American Medical Association looking at how vaccine requirements vary from state to state.

Some states, including California, allow parents to request a philosophical exemption from the vaccination requirement. Indiana does not give parents this option. The only exemptions available here are medical, which requires a doctor's signature, and religious.

Having a philosophical exemption offers much more leeway, Silverman said.

"It's pretty wide open as to what could qualify as a concern of yours that could qualify as an exemption," he said.

Also, Indiana requires parents to submit exemptions annually, ensuring that they remain firm in their commitment not to vaccinate their children.

"We ask them to do that annually because we know that some people may change their religious beliefs, so we just want to make sure that the child is as well-protected as the religion allows," Duwve said.

Still, there's more Indiana could do, Silverman said. Some states require that parents have their exemption request notarized, one potential barrier.

Others, such as New York, might more closely scrutinize the request for a religious exemption and deny it. A circuit court ruled this month that schools in New York can make vaccination a requirement for all children without violating the parents' constitutional rights.

In an attempt to get a better handle on how many children are vaccinated, Indiana in July will start requiring medical providers to enter immunization records for everyone 19 years and younger into the state's online registry.

Currently, the state's immunization registry does not necessarily include children who are home-schooled or younger than school age, unless a provider or school opts to enter the records.

Even without hard statistics that break down vaccination rates school by school or county by county, state health officials recognize that certain areas of the state tend to have lower vaccination rates than others.

Because some Amish don't believe in vaccination and there's a strong anti-vaccination movement in southern Michigan, there are pockets with low vaccination rates in Northern Indiana, Duwve said. These areas have seen outbreaks of another preventable disease, pertussis, or whooping cough, in recent years.

Indiana also has seen two measles outbreaks recently, one in the northern part of the state in 2011 and one in Central Indiana in 2012. In both instances, a person from overseas brought measles into this country, infecting a group of people who were largely unvaccinated. Each resulted in 14 cases.

The best way to protect against measles, health officials say, is to make sure that you're properly vaccinated, no matter your age. Once one case of measles hits a school, anyone who is not vaccinated and works at or attends that school will be asked to stay home until the outbreak is over.

For now, Hoosiers can take heart that Indiana has been immune.

"We kind of lucked out, because here in the Midwest we go to Disneyworld, not Disneyland," said Melissa McMasters, coordinator of the immunization and infectious disease program for the Marion County Health Department.

Call Star reporter Shari Rudavsky at (317) 444-6354. Follow her on Twitter: @srudavsky.