The Veterans Aging Cohort Study (VACS)-National: A Real-World Data Source Profile.

The Veterans Aging Cohort Study (VACS)-National is a large, longitudinal real-world data resource derived from electronic health records within the Department of Veterans Affairs (VA), the largest integrated healthcare system in the United States. As of December 2025, VACS-National includes > 14.9 million Veterans who have received care in the VA since 2000. It captures information on VA-related outpatient and inpatient care and includes structured (e.g., diagnostic codes, laboratory results, vital signs, dispensed medical products), semi-structured (e.g., radiology and pathology reports) and unstructured (e.g., progress notes) fields, collected from over 1300 points of care nationwide. Its longitudinal structure supports extended follow-up across demographically and clinically diverse populations within an integrated healthcare system. Key features for pharmacoepidemiological research include near real-time availability of data on dispensed medications, including biologics, vaccines, and devices; routinely-collected laboratory measurements; and computable phenotypes, including validated natural language phenotypes. The resource includes linkages to Centers for Medicare and Medicaid Services (CMS) data, VA Community Care data, National Death Index, and deeply phenotyped VACS sub-cohorts with an extensive library of biomarkers and survey data. VACS-National has supported a wide range of research, including drug utilization, drug safety, comparative effectiveness, and epidemiologic and health outcomes research. Strengths include its national scale, longitudinal follow-up, and rich clinical record; limitations include a small proportion of women and potential incomplete capture of care outside the system or not recoverable through linked datasets. VACS-National provides a comprehensive platform for generating real-world evidence to inform clinical, regulatory, and public health decision-making.