Cook County Confirms First 2025 Measles Cases

Public health officials have confirmed the first two measles cases of 2025 in Cook County, Illinois—one involving a vaccinated Chicago resident who traveled internationally through O’Hare Airport, and the other a suburban resident with unknown vaccination status who sought hospital care and was quickly isolated. Authorities have identified several public locations, including O’Hare Terminal 1 and local stores, as potential exposure sites and are urging anyone who visited these places on specified dates to contact healthcare providers if unsure of their vaccination status. The Chicago case is a rare breakthrough infection, illustrating that while vaccinated individuals can still contract measles, their illness is usually milder and less contagious. These cases occur amid a national measles resurgence, with 884 confirmed cases and three deaths reported across the U.S. in 2025. Health officials stress that two doses of the MMR vaccine provide 97% protection and recommend up-to-date immunization, especially for international travelers. The increase in cases is partly attributed to declining vaccination rates driven by misinformation.