Top 5 Takeaways

  1. Five measles cases in unvaccinated children: Occurred in children aged 1–9 years living in the same apartment building in Cook County, Illinois, highlighting measles’ high contagion among unvaccinated populations.
  2. Significant exposure risk: Approximately 400 people were exposed to measles, including vulnerable populations such as children under 1 year and immunosuppressed children.
  3. Complexity in outbreak control: The outbreak’s control involved identifying exposed individuals and administering MMR vaccines or immune globulin as post-exposure prophylaxis.
  4. Varied reasons for lack of vaccination: Cultural barriers, limited access to care, and vaccine refusal due to personal beliefs were factors contributing to the absence of vaccination among the affected children.
  5. Importance of MMR vaccination: The outbreak underscores the critical need for all eligible children and susceptible adults to receive two appropriately spaced doses of MMR vaccine to prevent measles and outbreaks.

Original Article Author and Citation

Corresponding Author

Kelley Bemis,

Suggested Citation

Bemis K, Frias M, Giovanni S, et al. Notes from the Field: Measles Outbreak — Cook County, Illinois, October–November 2023. MMWR Morb Mortal Wkly Rep 2024;73:229–230. DOI:


This MMWR article reports a measles outbreak in Cook County, Illinois, where five unvaccinated, vaccine-eligible children contracted measles. The outbreak was notable for occurring among children who lived in the same apartment building but did not socialize with each other, demonstrating measles’ ability to spread in dense living conditions among unvaccinated individuals.


The outbreak investigation involved identifying and managing exposed individuals through vaccination or immune globulin administration, with efforts complicated by the patients’ various reasons for being unvaccinated, including cultural barriers and vaccine hesitancy.


The report discusses the challenges in controlling measles outbreaks within communities with high rates of unvaccinated individuals. It highlights the need for tailored public health responses that account for cultural sensitivities and access issues, emphasizing the importance of vaccination in preventing such outbreaks.


The measles outbreak in Cook County, Illinois, serves as a reminder of the disease’s contagiousness and the critical role of vaccination in its prevention. It underscores the importance of ensuring all eligible individuals receive the MMR vaccine to prevent future outbreaks.

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