Measles in Illinois: What to know about vaccination rates

State public health data indicate that measles vaccination rates among Illinois schoolchildren exceed the threshold recommended to prevent outbreaks of the highly contagious viral infection.

On Feb. 16, the Illinois Department of Public Health reported the state’s first measles case of 2026, linked to a church in Collinsville where possible exposure may have happened on Feb. 8. On March 12, a confirmed measles case was announced by health officials in DeKalb County, tracked possibly to exposure at a local Walmart and post office.

The Cook County Health Department issued a warning on March 31 of possible measles exposures at O’Hare International Airport in Chicago and two locations in Niles, including a Fresh Farms grocery store and a Marshalls.

Cook County health officials said they’d tracked the possible exposures to a person who’d been contagious with measles at the time. That person also visited the Endeavour Health Immediate Care Center in Mt. Prospect days earlier.

In 2025, the U.S. marked its worst year for measles in more than three decades, The Associated Press reported. There were 14 cases in Illinois in 2025, according to the IDPH.

Although falling vaccination rates nationwide have concerned health officials, vaccination rates for measles in Illinois are at the threshold recommended for preventing outbreaks.

The best way to prevent measles infection is to get vaccinated, health experts said. The MMR vaccine – for measles, mumps and rubella – is commonly given to children over the age of 1.

“Because once you are exposed and unvaccinated, obviously, it’s too late for the vaccine,” DeKalb County Health Department administrator Lisa Gonzalez said. “So, know your vaccine status.”

The IDPH tracks vaccination rates based on school data. The data shows that more than 95% of Illinois students have been vaccinated for measles.

According to the U.S. Centers for Disease Control and Prevention, at least 95% of the population with both doses of the measles vaccine is effective in preventing outbreaks.

How is measles spread?

“Measles is a highly contagious viral disease that spreads easily from person to person through the air,” Gonzalez said.

According to the American Medical Association, “measles is one of the most contagious diseases and is transmitted by direct contact with infectious droplets and also via airborne spread when an infected person breathes, coughs or sneezes.”

Where do outbreaks tend to happen?

Measles outbreaks tend to occur in areas with low vaccination coverage. Common settings included crowded, enclosed spaces, such as schools, daycare centers, public transport, and healthcare facilities, according to the La Salle County Health Department.

What symptoms to look out for?

“Usually, the symptoms begin with fever, cough, runny nose, and red or watery eyes, but then it’s typically followed by a distinct rash that usually starts on the face and spreads downward,” Gonzalez said.

Measles starts with cold-like symptoms but includes a rash usually. While flu symptoms can be similar, people with the flu usually don’t develop a rash, and flu symptoms tend to be sudden and of abrupt onset, according to public health officials.

Can someone spread measles before they know they’re sick?

Someone with measles is contagious from four days before the onset date of the rash through the end of the fourth day after the onset of the rash (the onset date of the rash is called “day zero”), La Salle County public health officials said.

During this time, those infected should stay home and not attend work, school, or social activities unless they are seeking medical care. If seeking medical care, patients should call ahead to the medical facility and the local health department to make arrangements to minimize exposures.

Who is at the most risk?

Babies, older people, and those with compromised immune systems.

“We are concerned most about those who are unvaccinated,” Gonzalez said. “Measles can lead to serious complications, especially in young children, pregnant women, and people who already have a weakened immune system.”

What is the MMR vaccine?

The best way to prevent measles is through the MMR vaccine, which protects against measles, mumps, and rubella, according to public health officials. The vaccine keeps children from missing school or childcare, and adults from missing work to care for a sick child. Vaccination also limits the size, duration, and spread of outbreaks.

The measles vaccine is routinely recommended for children at 12 to 15 months of age, with a second dose recommended at 4 to 6 years of age. One dose of the MMR vaccine is required for those 12 months and older to attend child care facilities, and two doses of MMR are required in Illinois for kindergarten through 12th grade.