The coronavirus disease 2019 (COVID-19) pandemic pushed the European Union (EU) to centralize several public health functions. With the European Health Union (EHU) initiative, four reforms have been adopted to strengthen the EU’s health security framework: the extension of the European Medicines Agency and the European Centre for Disease Prevention and Control’s mandates, the creation of the Health Emergency Preparedness and Response Authority, and the upgrading of the Decision on serious cross-border threats to health. This article analyses the reconfiguration of authority patterns resulting from these reforms. It argues that the EHU exemplifies a distinct mode of integration (expansive unification) in which national sovereignty is not transferred to the center but is jointly exercised at the center. This mode of integration is suitable for capacity building in core state domains when functional needs confront reluctance from constituent units to surrender control.