The Central Registry of Patient Data is the most complex public information system in the Slovenian healthcare, providing valuable information to patients, healthcare professionals and health authorities. Its most important element is a Patient Summary, which contains essential clinical data required to ensure safe treatment of patients at a point of care. This article focuses on the Patient Summary and the review of its application aspects, especially in relation to the Vaccination Registry. The research employs a case study framework, supported by focus group discussions being a primary data collection technique. Single-entry collection and reuse of data, as implemented in the case of Patient Summary, could significantly optimize current practices and necessary resources for processing health data. Moreover, the research reveals that structured and standardized data from the Patient Summary could provide an important input for primary use and other applications across the digital landscape in the Slovenian healthcare system.