Public health surveillance data: legal, policy, ethical, regulatory, and practical issues.

In the United States, data systems are created by the ongoing, systematic collection of health, demographic, and other information through federally funded national surveys, vital statistics, public and private administrative and claims data, regulatory data, and medical records data. Certain data systems are designed to support public health surveillance and have used well-defined protocols and standard analytic methods for assessing specific health outcomes, exposures, or other endpoints. However, other data systems have been designed for a different purpose but can be used by public health programs for surveillance. Several public health surveillance programs rely substantially on others' data systems. An example of data used for surveillance purposes but collected for another reason is vital statistics data. CDC's National Center for Health Statistics (NCHS) purchases, aggregates, and disseminates vital statistics (birth and death rates) that are collected at the state level. These data are used to understand disease burden, monitor trends, and guide public health action. Administrative data also can be used for surveillance purposes (e.g., Medicare and Social Security Disability data that have been linked to survey data to monitor changes in health and health-care use over time).