SSN Justification Memo

22MAY2024

MEMORANDUM FOR THE RECORD
SUBJECT: JUSTIFICATION FOR THE USE OF THE SOCIAL SECURITY NUMBER IN
DEPARTMENT OF DEFENSE (DOD) MILLENNIUM COHORT PROGRAM (MCP)
(NHRC.2000.0007)
1. This memorandum is to satisfy the requirements of the Department of Defense Instruction
(DoDI) 1000.30, Reduction of Social Security Number (SSN) Use Within DoD, dated August
1,2012, that requires justification of the necessity for the continued collection of SSNs in the
MCP.
2. The FY1999 National Defense Authorization Act directed the Secretary of Defense “ to
establish a center devoted to a longitudinal study to evaluate data on the health conditions of
members of the Armed Forces upon their return from deployment on military operations for
purposes of ensuring the rapid identification of any trends in diseases, illnesses, or injuries
among such members as a result of such operations.” In response, the Naval Health Research
Center was designated as the DoD Center for Deployment Health Research and the Millennium
Cohort Study was established.
The purpose of the information collected by the Millennium Cohort Program, made up of the
Millennium Cohort Study and the Millennium Cohort Family Study, is to assist US policy makers
with understanding how military service and experiences can impact the long-term health and
well-being of service members and Veterans. Specifically, the Millennium Cohort Program
seeks to track the physical and psychological health of service members and Veterans, identify
exposures and behaviors that increase the risk of disease, and evaluate the impact of military
life on the health and well-being of military families.
3. As documented in FY1999 National Defense Authorization Act (TAB A), System of
Records Notice N06150-5 (TAB B), Report Control Symbol # DD-NAVY-2678 (TAB C), and
Office of Management and Budget Approval # 0703-0064 (TAB D), data collected for the
Department of Defense (DoD) Millennium Cohort Program includes the capture of SSNs. The
Millennium Cohort Program is utilized to collect information from over 261,000 US service
members and 28,095 military spouses for the purpose of computer matching of records. All
Millennium Cohort Program data, including survey data, data extracted or received from DoD
sources, and data from non-DoD agencies or institutions, are stored and analyzed on accesscontrolled folders located on the Naval Health Research Center’s servers. As a DoD
organization, Naval Health Research Center must have appropriate administrative, technical,
and physical safeguards to protect the privacy of PII/PHI and to mitigate any intentional or
unintentional use or disclosure that is in violation of the standards, implementation
specifications, or other requirements.
4. The justification(s) for the use of the SSN for the MCP is based on compliancy with DoDI
1000.30, Enclosure 2, Paragraph 2.c.(8) Computer Matching, DoDI 1000.30, Enclosure 2,
Paragraph 2.c.(11) Legacy Systems Interface, and DoDI 1000.30, Enclosure 2, Paragraph
2.c.(13) Other Cases.

5. Acceptable use 2.c.(8), Computer Matching, applies because the MCP matches existing
spouse and service member records or specimens to those contained in electronic data sources
maintained by the DoD and other agencies such as the Department of Veterans Affairs (VA;
SSNs for matching will be destroyed prior to data analyses). The use of SSN as a unique
identifier is needed for this database where there is potential for duplicate registration and no
other means of unique identification exists. Furthermore, because the enrollment of service
members into the Millennium Cohort Study preceded the widespread adoption of the 10-digit
DoD Identification Number (DoD ID) derived from the DoD Electronic Data InterchangePersonal Identifier (EDIPI), the SSN is the only unique identifier available for all study
participants.
6. Acceptable use 2.c.(11), Legacy Systems Interface, applies because the EDIPI does not
transfer or serve as a personal identifier across the information systems and collections
deployed across the Services or within the Military Health System. The service member and
spouse SSN must be collected until all systems that are sources for data input to the MCP are
integrated and able to utilize DoD ID Numbers for patient identification purposes.
7. Acceptable use 2.c(13), Other Cases, applies because SSNs are the only unique identifier
consistently used by all databases maintained by the DoD, VA, and non-DoD databases that
are linked with MCP databases. While current files from MCP use the DoD ID, the historical
records and non-DoD databases only contain the SSN, therefore, there is no way to link the
data with confidence. Using the SSN to link the data records from different sources is required
to ensure continuity, quality, and integrity of the data system over time.
8. Objectives of the MCP include the ascertainment long-term health outcomes that may be
associated with military service, to assess the associations of military service on the health and
well-being of military families and to compare the adjusted probabilities of new onset diseases
and conditions. The studies generated from the MCP utilize data already collected in existing
Military Health System IT systems and electronic collections, Department of Navy systems,
Defense Manpower Data Center, and other non-DoD administrative databases. Because
ascertainment of long-term health and well-being extends beyond the period of military service,
an interagency agreement has been established with the VA to access and link VA electronic
health records and benefits data with MCP data. These data from multiple sources are merged
and directed for analyses to examine potential associations between risk factors (including
demographics, military characteristics, and potential environmental exposures) and short-term
and long-term health outcomes. The nature of data analysis activities requires linking data to the
same individuals across multiple systems using the SSN as the common unique identifier.
9. MCP SSN mitigation includes use of role-based access and employs appropriate technical,
physical, and administrative controls to ensure that users have access to only the specific data
needed to perform research and mission related activities. Additionally, periodic audits are
conducted to ensure proper use of the program data. Data is used exclusively by authorized
Department of Defense (DoD) personnel and DoD contractors. Only users with Government
approved accounts and a need to know can view data through a Common Access Card (CAC)
enabled authentication process. Access to the data center where PII is stored is restricted to
authorized personnel only; and will only be stored and accessible from one site: Naval Health
Research Center (NHRC) San Diego, CA. The Bureau of Medicine and Surgery is modifying
SORN, “Health Care Record System,” N6150-2 to include the DoD ID or EDI-PI as part of its
mitigation plan. As more legacy systems remove or truncate the SSN, the MCP database will be
able to transition to alternative identifiers in the future.

10. Justification for the use of the SSN does not constitute blanket permission to use the SSN.
NHRC has made a thorough effort to evaluate the risk associated with its use and every
reasonable step has been (or is being) taken to reduce the use of the SSN and protect the SSN
where its use is still required.
11. For questions related to this memorandum contact me by telephone at (619) 553-9267 or
email: [email protected].

RULL.RUDOLP
H.P.1502507970

Digitally signed by
RULL.RUDOLPH.P.1502507
970
Date: 2024.05.22 11:17:26
-07'00'

_____________________________________
Rudolph Rull, PhD
Principal Investigator
Naval Health Research Center