This Medical Data Breach Put the Information of 5.5 Million Patients at Risk
Data breaches targeting healthcare and compromising patient information seem to be coming fast and furious, the latest of which occurred at Yale New Haven Health (YNHHS), a large nonprofit healthcare network in Connecticut. Hackers stole the data of more than 5.5 million people during an attack in March 2025.
Other major cyber incidents revealed by health care organizations in recent weeks include Google sharing the data of 4.7 million Blue Shield of California members , as well as a hack at Frederick Health Medical Group in Maryland that affected nearly a million patients .
What happened at Yale New Haven?
According to a public notice on the YNHHS website, on March 8, 2025, the organization detected “unusual activity” in its system, which was later identified as unauthorized third-party access that allowed attackers to copy certain patient data. While the information stolen varies depending on the individual, it may include the following:
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Name
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Date of birth
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Address
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Phone number
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Email address
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Race
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Ethnicity
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Social Security number
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Patient type
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Medical card number
YNHHS says the breach did not include access to medical records, treatment information or financial data (such as billing and payment information).
What to do if your records have been affected
If you were a patient in the YNHHS network, your data may have been compromised. The organization began sending out notifications to victims on April 14, so keep an eye out for the letter in the mail.
YNHHS provides free credit monitoring and identity protection services to patients whose Social Security numbers have been stolen, with instructions for using these services allegedly included in mailed notifications. You can call the Help Line at 855-549-2678, Monday through Friday, 9:00 a.m. to 9:00 p.m. ET if you have questions about the incident or how it may affect you.
Class action lawsuits are also being prepared to seek damages for those affected by the breach, so you may want to stay tuned for updates on those claims.
As always, you can’t get back stolen data, but you can minimize the potential negative impact on your life. Freeze your credit, post a fraud alert, and request copies of your credit report regularly. Block your Social Security number to prevent identity theft. You should also review medical bills and statements from YNHHS and report any discrepancies immediately. Practice good digital hygiene, such as avoiding clicking links in messages you receive.