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The National Clinical Cohort Collaborative (N3C), originally launched as the National COVID Cohort Collaborative, is a centralized biomedical data repository and analytics platform run by the National Center for Advancing Translational Sciences (NCATS) at the National Institutes of Health (NIH). NCATS states that more than 90 institutions worked together to build it, and that it is now using the original N3C infrastructure to expand into new disease domains. Authorized investigators work with electronic health record (EHR) data inside a secure cloud enclave, the N3C Data Enclave, rather than receiving data files.
What It Is
N3C pools EHR-derived data that has been harmonized to the OMOP Common Data Model, covering demographics, lab results, procedures, medications, conditions and physical measurements. Research teams use the enclave for observational studies, and work of this kind is usually planned with the same rigor as clinical trial protocol design.
The enclave is the only place where N3C data can be accessed and analyzed. NCATS states that data cannot be downloaded from the enclave or removed from it. Users may download aggregated research results only after review by a data download committee. The platform in use is Palantir Foundry, hosted in Amazon Web Services, in a FedRAMP-certified cloud environment with encryption in transit and at rest.
Who Runs It and What It Covers
NCATS operates N3C. According to its program page, the enclave currently includes these areas:
- Long COVID Tenant: described by NCATS as the largest open U.S. database for ongoing Long COVID and COVID-19 research.
- Clinical Pilots: real-world clinical data on chronic kidney disease and cancer.
- Education Tenant: simulated data from 500,000 patients for practicing real-world data analysis.
- Dynamic Tenants: project-specific environments built from approved requests.
N3C Data Access Tiers and Governance
N3C offers three data levels, which differ in how much identifying detail they keep. NCATS notes that data access requirements may change over time, so check its data overview page before applying.
| Data Access Tier | What the Data Contains | Who Is Eligible | Access Requirements (per NCATS) |
|---|---|---|---|
| Synthetic Data Set | Computationally generated from the Limited Data Set; mirrors patient data statistically but contains no actual patient records. | US-based and foreign institution researchers, plus citizen scientists. | N3C registration, Enclave account, Data Use Agreement (DUA) with NCATS, NIH IT training, approved Data Use Request (DUR). |
| De-identified Data Set | Dates of service are algorithmically shifted; ZIP codes are cut to three digits, or removed for areas under 20,000 people or Tribal lands. | US-based and foreign institution researchers. | The synthetic requirements plus Human Subjects Research Protection training. |
| Limited Data Set (LDS) | Retains dates of service and patient ZIP code. | Researchers at US-based institutions only. | The de-identified requirements plus a local IRB determination letter. |
How to Access and Use the N3C Enclave
The NCATS pages describe this sequence:
- Institutional DUA: The institution signs a Data Use Agreement with NCATS. This umbrella agreement must be in place before any of its researchers can submit a Data Use Request.
- Register and get an Enclave account: Complete N3C registration and create an N3C Data Enclave account.
- Training: Complete NIH IT training and, for the de-identified and Limited Data Set tiers, Human Subjects Research Protection training.
- Submit a Data Use Request (DUR): A DUR includes the project title, personnel names, a non-confidential research statement, the proposal and the requested access level. Applicants agree to the N3C Data User Code of Conduct.
- Data Access Committee review: The N3C Data Access Committee reviews and approves DURs. Project workspace access is effective for one year from the date access is granted, and Data Use Requests are renewable.
- Analyze inside the enclave: All work takes place on the NCATS platform, and data may be used only for the approved research purposes.
- Request aggregated results: Aggregated results can be downloaded only after review by the data download committee.
Governance of this kind sits alongside the wider expectations of Good Clinical Practice, and registration duties for interventional studies are covered in clinical trial registration and reporting compliance.
Strengths and Limits
- Strengths:
- Data from many institutions harmonized to one common data model, so the same query logic applies across sources.
- A synthetic tier that lets people, including citizen scientists, practice before requesting real data.
- A single secured platform for analysis, with protections such as encryption in transit and at rest.
- Limits:
- Data cannot be downloaded; only reviewed aggregated results leave the enclave.
- The Limited Data Set is open only to researchers at US-based institutions.
- Access is project-based, runs for one year at a time and needs an institutional DUA first.
- As with any EHR-derived data, results depend on how the contributing institutions recorded care.
Alternatives and Related Data Platforms
Other multi-center resources serve different needs, and their access rules differ from those of N3C. See each operator’s own site for current terms. For background on the secure environment model, see secure data enclave.
| Platform / Network | Operator | Notes |
|---|---|---|
| N3C Data Enclave | NIH / NCATS | Harmonized EHR data in a cloud enclave; Long COVID, clinical pilots, education and dynamic tenants. |
| All of Us Research Program | NIH | A separate NIH research program with its own data access process. |
| PCORnet | PCORI | A national network of health systems for patient-centered research. |
| TriNetX | TriNetX, LLC | A commercial federated health data network. |
| OHDSI | OHDSI community | An open community built around the OMOP Common Data Model. |
Frequently Asked Questions
What does N3C stand for?
N3C stands for the National Clinical Cohort Collaborative. It began as the National COVID Cohort Collaborative, and NCATS now uses the infrastructure to expand into new disease domains.
What is the N3C enclave?
The N3C Data Enclave is the secure NCATS cloud platform, built on Palantir Foundry hosted in Amazon Web Services, where approved users analyze N3C data.
Can international researchers access the N3C Data Enclave?
Yes, with limits. Researchers at foreign institutions can request the de-identified and synthetic data sets. The Limited Data Set is for researchers at US-based institutions. Access requires an approved Data Use Request under an institutional DUA.
Is IRB review required for N3C?
It depends on the data level requested. NCATS lists a local IRB determination letter as a requirement for the Limited Data Set, and not for the de-identified or synthetic tiers. Human subjects research training applies to the de-identified and Limited Data Set tiers.
Does N3C allow downloading patient-level data?
No. NCATS states that data cannot be downloaded from the enclave or removed. Aggregated results can be downloaded after review by a data download committee.
How long does access last?
Project workspace access is effective for one year from the date it is granted, and Data Use Requests are renewable.
Sources
Checked November 7, 2026.
- NCATS, NIH. “National Clinical Cohort Collaborative (N3C).” https://ncats.nih.gov/research/research-activities/n3c/overview
- NCATS, NIH. “N3C Enclave Data Overview.” https://ncats.nih.gov/research/research-activities/n3c/data-overview
- NCATS, NIH. “N3C Enclave Frequently Asked Questions.” https://ncats.nih.gov/research/research-activities/n3c/faqs
- Haendel MA, Chute CG, Gersing K, et al. “The National COVID Cohort Collaborative (N3C): Rationale, design, infrastructure, and deployment.” Journal of the American Medical Informatics Association, 2021;28(3):427-443. https://doi.org/10.1093/jamia/ocaa196
