Illinois’ high vaccination rate has stemmed measles tide amid nationwide spike

In 2000, public health experts declared the United States had eliminated measles based on the “absence of the continuous spread of disease” for more than 12 months.

Centers for Disease Control and Prevention officials called it a “historic public health achievement,” which they credited to a “highly effective vaccination program” and “better measles control in the Americas,” even as they acknowledged the occurrence of small outbreaks in under-vaccinated communities and cases resulting from unvaccinated international travelers.

This year, however, the U.S. is in the midst of its largest measles outbreak in 35 years.

As of Aug. 20, the CDC had confirmed 2,777 cases in 46 states and the District of Columbia, including two fatalities in Pennsylvania. That exceeds the 2,289 cases reported in 45 jurisdictions during all of 2025.

But in Illinois, “We haven't had a surge in measles cases thanks to (the state's) overall high vaccination rate,” said Dr. Jennifer Seo, pediatric medicine medical adviser for the Illinois Department of Public Health.

Five cases have been reported in Illinois this year, Seo said, compared to 14 cases in 2025 and 67 in 2024, which included an outbreak in a Chicago shelter.

Among the five Illinois cases includes an unvaccinated student at Kaneland High School. Kane County Health Department officials reported that exposures may have occurred at the Maple Park high school on Aug. 18, and at the Next Generation Pediatric Clinic in South Elgin on Aug. 21.

Measles symptoms typically develop seven to 21 days after exposure, according to health professionals, and can include high fever, cough, runny nose and red or watery eyes. Several days later, a red, blotchy rash develops near the hairline and spreads downward across the body.

An update Saturday on the health department website indicates the unvaccinated individual was no longer infectious as of Aug. 25.

Except for infants 6 months and younger, pregnant women and immunocompromised people, for whom the MMR (measles, mumps, rubella) vaccine is not recommended, Seo and other Illinois health officials urge adults and children be up-to-date on measles vaccinations to protect themselves from infection.

“The vast majority of people who get measles have not had a vaccination or have an unknown vaccination status,” Seo said. “If you’re vaccinated and you get measles, the symptoms are much less severe and you won’t be able to spread the infection as readily.”

Two doses of the MMR vaccine are about 97% effective at preventing measles, according to the CDC. Those doses typically provide long-term protection.

However, health officials are seeing a decline in measles vaccinations, said Dr. Rashmi Chugh, medical officer with the DuPage County Health Department.

Chugh cited CDC statistics which indicate vaccination rates among U.S. kindergarten students at 92.4% for the 2025-26 school year, down from 95.2% for the 2019-20 school year.

In Illinois, vaccination rates were slightly higher, with 92.8% of kindergartners vaccinated during 2025-26, compared to 96.6% vaccinated in 2019-20, according to Chugh.

The CDC recommends children get two doses of the MMR vaccine: the first when they're between 12 and 15 months old and the second between the ages of 4 and 6 years, before they start school.

“In suburban Cook County, the number of school-age children who are not protected against vaccine-preventable diseases has nearly doubled over the past decade,” noted Cook County Department of Public Health Director of Communications Efrat Dallal Stein. “Nearly 12,000 students were unprotected during the 2025-2026 school year.”

Given the vaccination rate decline, “it's more important than ever to empower parents to stay informed … to protect their little ones and the community,” said Chugh, who encourages parents or guardians to consult their health care providers to ensure youngsters are on track with vaccinations.

“We believe all parents want to do what’s best for their children,” she said. “We try to meet people where they are and follow evidence-based recommendations.”

According to the Cook County health department, the measles virus can remain in the air for up to two hours after an infected person leaves an area. Additionally, one person with measles can infect nine out of 10 unvaccinated people who are exposed, according to Stein.

Both Seo and Chugh advise it’s not too late for certain unvaccinated people exposed to the virus to get the vaccine. An unvaccinated person has 72 hours post-exposure to get a vaccination.

“The challenge is people might not realize they have measles and are spreading it,” said Seo, adding that the CDC also recommends that people who cannot get the MMR vaccine receive a post-exposure prophylaxis called immunoglobulin, which can be effective if administered within six days of the initial measles exposure.

Chugh notes measles complications can include pneumonia, encephalitis and other conditions that can lead to hospitalization and even death.

“Measles is a vaccine-preventable disease,” she said. “We’re fortunate to have the tools and resources to prevent the illness and its spread.”

bvitello@dailyherald.com