Challenges and opportunities of integrating NFDI4Health into the European Health Data Space

Introduction: The European Health Data Space (EHDS), launched in 2025 with implemen-tation within four years, aims to enable access to and cross-border exchange of health data to improve healthcare, policy and research [1]. As a national consortium within Germany's na-tional Research Data Infrastructure (NFDI), NFDI4Health contributes to this European en-deavour by developing standards and infrastructure to ensure the secure and efficient ex-change and us of health data. In particular, NFDI4Health provides already an interoperable metadata schema, a central search infrastructure and aims to serve as a decentralised HealthData Access Body (dHDAB) within EHDS. Feedback on the EHDS metadata catalogue Health DCAT-AP: NFDI4Health devel-oped early a modular metadata schema (MDS) [2], [3], already used by its services [4]. It de-scribes clinical, epidemiological and public health studies based on standards like DataCite and aligned with registries such as ECRIN MDR. It uses terminologies like SNOMED CT, ICD-10 and NCI Thesaurus and is represented in the FHIR standard [5]. A recent comparison with the MDS revealed limitations in the unstructured mandatory fields of Health DCAT-AP. We propose extensions to support health-specific metadata, such as structured elements for study design, sampling and data sources. Health-specific terminologies should replace generic ones to improve interoperability, semantic precision and secondary data use. Central metadata search: To support metadata discovery, NFDI4Health operates the Health Study Hub [6], a web-based platform, connecting data producers and users in clinical, public health and epidemiological research. Aligned with EHDS goals, it could serve as a na-tional catalogue of German health studies. It promotes responsible secondary data use and cross-border interoperability by enabling the publication and discovery of FAIR metadata, sup-porting data reuse within legal and technical constraints. The Hub aggregates data from public repositories, offers semantic search and supports integration via API or forms. Originally launched during the COVID-19 pandemic, it currently hosts over 43.000 resources. The plat-form fosters transparent research and enhances Germany's readiness for EHDS integration. Access and Secure Processing: In addition to metadata services, NFDI4Health is pre-paring to assume the role of a dHDAB under the EHDS framework. A key function of a HDAB is enabling data access and providing a secure processing environment. NFDI4health collabo-rates closely with the Medical Informatics Initiative to further develop the German Portal for Medical Research Data to facilitate requests for study data centrally. For secure processing, two distributed data analysis frameworks have been piloted [7], [8]. Moreover, NFDI4Health has intensified its dialogue with national and international developers and providers of secure processing environments to integrate further processing environments. An international work-shop is planned by NFDI4health for August 2025. Conclusions: NFDI4health is strongly committed to harmonising its standards and services closely with the structure of the EHDS and ensuring broad compatibility. For enhanced in-teroperability, we align our metadata schema with HealthDCAT-AP and feed our findings from practical use [9] back into the EHDS development process. As NFDI consortium, we support the development of the European Open Science Cloud (EOSC). As partner of the EOSC Health Data Taskforce, we support the alignment of health infrastructures at the European level.