This Healthcare Data Breach Compromised 5.5 Million Patients' Information

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 massive nonprofit healthcare network in Connecticut. Hackers stole the data of more than 5.5 million individuals during an attack in March 2025.

Other major cyber incidents revealed by healthcare organizations in recent weeks include Blue Shield of California's exposure of 4.7 million members' data to Google along with a breach at Maryland's Frederick Health Medical Group, which affected nearly a million patients.

What happened at Yale New Haven Health?

According to a public notice on the YNHHS website, the organization discovered "unusual activity" on its system on March 8, 2025, which was later identified as unauthorized third-party access that allowed bad actors to copy certain patient data. While the information stolen varies by individual, it may include the following:

• Name

• Date of birth

• Address

• Phone number

• Email address

• Race

• Ethnicity

• Social Security number

• Patient type

• Medical record number

YNHHS says the breach did not include access to medical records, treatment information, or financial data (such as account and payment information).

What to do if your records were affected

If you've been a patient in the YNHHS network, your data may have been compromised. The organization began sending notices to those affected on April 14, so keep an eye out for a letter in the mail.

YNHHS is providing complimentary credit monitoring and identity protection services to patients whose Social Security numbers were stolen, with directions for taking advantage of these services presumably included in the mailed notices. You can call the support line at 855-549-2678 Monday to Friday between 9 a.m. and 9 p.m. ET if you have questions about the incident or how you may be affected.

There are also class action lawsuits in the works seeking damages for individuals impacted by the breach, so you can keep an eye out for news on those filings.

As always, you can't reclaim stolen data, but you can minimize the potential negative impact on your life. Freeze your credit, place a fraud alert, and request copies of your credit report regularly. Lock down your Social Security number to prevent identity theft. You should also review medical bills and statements from YNHHS and report any discrepancies immediately. Exercise good digital hygiene practices, such as avoiding clicking links in messages you receive.

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