What is your school's measles vaccination rate?

This story has been updated to correct an error in a caption regarding the type of vaccine being given.

Your children might be vaccinated against measles, but what about their classmates?

Only 9.8 percent of public and private schools across the suburbs have 100 percent of the student population vaccinated against measles, and some have immunization rates below 80 percent, according to data compiled by the Illinois State Board of Education.

With recent measles outbreaks reported across the country, local experts urge families to make sure their vaccinations are up to date to protect themselves and others against the fast-spreading disease.

A 93 percent to 95 percent measles vaccination rate is required to stop the spread of a contagious disease within a population, a concept health experts refer to as "herd immunity," according to the World Health Organization. The chance of a measles outbreak rises if protection levels fall below that threshold, said Dr. Andy Bernstein of North Suburban Pediatrics in Buffalo Grove and Evanston.

"It can catch on like wildfire," he said. "It's a highly contagious disease, and as soon as immunization rates in a community drop with any significance, it spreads very easily."

Illinois is among six states said by the Centers for Disease Control and Prevention to have an outbreak, with five cases in January and February. One person arrived on a flight to Midway Airport in Chicago and days later sought care at Northwestern Medicine Delnor Hospital in Geneva, causing the Illinois Department of Public Health to issue a public warning to people who might have been exposed.

Illinois requires schoolchildren to be vaccinated against measles and a bevy of other communicable diseases, from polio to chickenpox to diphtheria, pertussis and tetanus.

For measles, nearly 94 percent of schools in suburban Cook and the collar counties fall within or above the range for achieving herd immunity, state records show. Many institutions below that level have more students legally exempted because of religious objections to getting the shots.

A medical objection, such as a compromised immune system or a severe allergic reaction to vaccinations, is the only other valid reason for schoolchildren to be exempted from vaccines in Illinois, ISBE spokeswoman Jackie Matthews said.

A philosophical exemption is allowed in some parts of the country, though Congress has been discussing banning all exemptions other than medical. California, West Virginia and Mississippi are the only states so far to do so.

Under the McKinney-Vento Act, homeless students also are not required to provide proof of immunization in order to start attending school. While understanding their protected rights, Palatine Township Elementary District 15 officials take extra steps to ensure those students receive their required shots, spokeswoman Morgan Delack said.

"We really try to work with our families who fall into that category ... and provide them access to medical clinics to get vaccinated," she said.

Palatine schools were on high alert during a 2015 measles outbreak at a local day care center, prompting some parents to get their children vaccinated earlier than usual, Delack said. Four years later, "we don't generally have a lot of concern" that such an outbreak would occur within District 15, she said. "We have a very high percentage of students who are vaccinated."

At nearly 92 percent, Lake Louise Elementary School had the district's lowest immunization rate in 2017-18, according to ISBE data. Other District 15 schools ranged between 95 and 99 percent.

Among suburban schools, 76 had vaccination rates below 90 percent for measles, meaning one student in 10 is unvaccinated. Nearly all are private schools, but South School in Westmont, Grass Lake Elementary School in Antioch and Country Meadows Elementary School in Long Grove are in that category.

Children typically receive their first measles vaccine at 12 months old and a second between the ages of 4 and 6, said Dr. Tina Tan, an infectious disease specialist with the Ann & Robert H. Lurie Children's Hospital of Chicago. The vaccination is 93 percent effective after the first dose and 97 percent after the second, according to the CDC.

Though the likelihood that an immunized person would contract the disease is very low, Bernstein said, "no vaccine is 100 percent." To complicate the issue even more, he said, a person could be contagious for up to four days before showing signs of the measles.

Among the most vulnerable to measles are medically exempt kids, adults with weakened immune systems, and babies under age 1 who haven't received the vaccination yet, Bernstein said. Even fully immunized patients can be at risk if they're on certain medications, such as chemotherapy, steroid treatment or anti-inflammatory drugs - "anything that weakens the immune system," he said.

Public health concerns relating to immunization have increased globally as more people have been adopting anti-vaccination practices, Tan said. "Vaccine hesitancy" was listed by the World Health Organization as one of the top 10 global health threats in 2019.

Much of the hesitation likely comes from misinformation found on the internet and social media claiming vaccines can lead to neurological problems, Tan said, noting there is no scientific data showing any correlation.

A study published last week in the Annals of Internal Medicine affirmed there is no link between the measles, mumps, rubella vaccine and autism after a study of 657,461 children in Denmark.

One group that has historically received a religious exemption is Christian Scientists, whose spiritual practices rely on prayer for healing. But the church also is cognizant of public health concerns, obeys the laws and maintains strong relationships with local health departments, said Tim Mitchinson, of the Christian Science Committee on Publication for Illinois.

In a statement released last month, Christian Science Committee leaders said members of the denomination are free to decide to vaccinate their children. "Whatever the right legislative answer may be ... at this time, Christian Scientists hope that their long experience as a religious minority working in cooperation with society's majority might point to the possibility of a resolution based on mutual respect and understanding in the best interest of all."

The recent measles cases reported around the country, if nothing else, have brought awareness to an important issue, Bernstein said, noting health officials everywhere are working to correct misconceptions.

"We're lucky to live in the U.S. where you can get these vaccines so easily, and I'm glad it's being discussed," he said. "Vaccines are important, safe, and there's literally nothing to be worried about."