Michigan Medicine says the health information of 1,015 patients was potentially exposed when it mailed out postcards without envelopes. 

According to Michigan Medicine, a research study postcard was sent to prospective participants on June 27, 2025. Those postcards were mailed without envelopes and contained a "limited amount" of protected health information that might have been exposed by anyone who handled the postcards. 

An investigation by the health system found that the University of Michigan's Institutional Review Board, which is responsible for the oversight of human subject research, mistakenly approved the use of the postcards. 

Michigan's Institutional Review Board is taking steps to ensure that a similar incident does not happen again, Michigan Medicine said in a statement. 

"We take patient privacy very seriously, and we regret this incident. Whenever situations like this occur, we immediately take steps to investigate," said Jeanne Strickland, Michigan Medicine Chief Compliance Officer, in a statement. "We will analyze this incident and review our safeguards and make changes if needed to protect those we care for." 

Michigan Medicine says it mailed notices to patients affected by the incident on Aug. 14. 

Those who are concerned about the breach and who did not receive a notice letter can call the Michigan Medicine Assistance Line at 1-833-353-4105, Monday through Friday, from 9 a.m. to 9 p.m. 

Although Michigan Medicine believes the risk of medical or identity theft is low with this incident, it encourages impacted patients to monitor their health insurance statements for any evidence of fraudulent transactions.