COOK COUNTY (WLS) -- A data breach has targeted Cook County Health patients.
An unauthorized person accessed a vendor's system where patient data was stored back in April, the health system said.
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Records for 1.2 million patients were impacted.
The data accessed includes dates of birth, addresses and medical information, the health system said. Approximately 2,600 of the patient records may have also included Social Security numbers.
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Cook County Health plans to send letters to impacted patients next week.