A nationwide analysis conducted by NBC News’ Health and Medical Unit, in collaboration with Stanford University researchers, reveals a troubling trend: since 2019, 77% of counties and jurisdictions across the United States have experienced a decline in measles vaccination rates.
The measles, mumps, and rubella (MMR) vaccine — once credited with eliminating measles in the U.S. by 2000 — is now falling below the threshold needed to maintain herd immunity in many communities.
NBC 5 Responds took a closer look at how this trend is playing out in the Chicago area.
A look back and a warning ahead
Dr. Stockton Mayer, interim chief of infectious diseases at UI Health, told NBC Chicago the United States saw half a million measles infections every year, resulting in about 500 deaths annually, before the introduction of the MMR vaccine in 1963.
Measles was eliminated in the United States by 2000. But as cases continue to increase this year, the U.S. is now at risk of losing that status, Mayer said.
Herd immunity slipping
According to the joint NBC News-Stanford University analysis, 97.58% of kindergarteners were immunized with the MMR vaccine in 2014. By 2024, that number had dropped to 94.89% — just below the 95% threshold recommended by the CDC to maintain herd immunity.
“Herd immunity is the level of immunity at which transmission of a virus becomes very difficult,” Mayer said. “If you don’t have that threshold, particularly for a virus like measles, there’s a risk of transmission within that community.”
Chicago-area schools falling short
NBC 5 Responds reviewed publicly available student health data from the Illinois State Board of Education, analyzing records from more than 2,900 public and private schools in the Chicago area.
In 2024, one in four schools reported MMR vaccination rates below the herd immunity threshold.
Among the districts with the lowest reported rates were Alsip-Hazelgreen-Oak Lawn School District 126 in Cook County, Zion Elementary School District 6 in Lake County and Chicago Public Schools.
District 126 reported 87.51% of students were vaccinated, but the superintendent told NBC Chicago the district did not submit all records in time for state analysis and claimed the actual rate was 97.8%.
Meanwhile, District 6 reported 72.3% of students were vaccinated. The district attributed the decline to “shifting demographics, policy landscapes, access barriers, misinformation, and data/measurement changes,” and emphasized its commitment to a safe learning environment.
Chicago Public Schools reported a 93.05% vaccination rate. As of publication, CPS has not responded to NBC Chicago’s request for comment.
See vaccine rates for your school district
Use this tool to check the most recent measles vaccination rates – as reported to the Illinois State Board of Education – at most private or public schools in the Chicago area.
What’s driving the decline?
Mayer points to several factors contributing to the drop in vaccination rates.
“There are misconceptions about what vaccines do, concerns about side effects, distrust in the healthcare community, and even fears related to immigration status,” he said.
He encourages parents to speak with their child’s pediatrician if they have questions about the vaccine.
“We have to follow the science, support what we know works, and really back that as a community,” Mayer said.
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