By 2025-2026, healthcare vendor supply chain attacks had become the dominant breach vector in US healthcare, with HHS OIG and OCR reporting that third-party vendor incidents accounted for over 60% of significant healthcare data breaches. The cascading nature of healthcare supply chain breaches is documented across multiple incidents: Change Healthcare (100M affected through a single billing clearinghouse), Welltok MOVEit (8.5M through a patient engagement SaaS), Medical Informatics Engineering/WebChart (3.9M through an EHR vendor), AMCA (20M through a billing collections vendor), PJ&A transcription (9M through a medical transcription service), and Eye Care Leaders (3.6M through an ophthalmology EHR vendor). HHS’s 2024 healthcare cybersecurity report identified vendor concentration as the single greatest systemic risk to the sector. ISMG Editors noted in April 2026 that five vendor incidents in the first quarter of 2026 (including CareCloud’s SEC notification, the orthopedic device maker breach, and the hospital ambulance diversion incidents) demonstrated that vendor risk remains inadequately controlled despite years of warnings. Key structural vulnerabilities documented: (1) Most hospitals lack visibility into their vendors’ security posture; (2) Standard business associate agreements (BAAs) under HIPAA lack enforceable security requirements; (3) Healthcare consolidation creates single points of failure as dominant vendors serve hundreds of systems; (4) OT/clinical system downtime during vendor outages directly threatens patient safety. HHS’s proposed updates to HIPAA Security Rule (January 2025) include mandatory vendor security assessments and 24-hour breach notification requirements.