Centene Corporation, a US health insurer lost the medical records of nearly a million people back in 2016.
The incident came to light when six hard drives containing the customer information including names, addresses dates of birth, social security numbers, and membership details of about 950,000 people were lost.
Centene notified all the impacted citizens of the breach.
Source: https://www.bbc.com/news/technology-35420306
"id": "CEN18136522",
"linkid": "centene-corporation",
"type": "Breach",
"date": "01/2016",
"severity": "85",
"impact": "5",
"explanation": "Attack threatening the organization's existence"