In recent IR literature, the term “regime complexity” has described the phenomenon that international regimes are increasingly overlapping, involving more institutions and actors. Pandemic prevention using a One Health approach represents one example of regime complexity as health threats for humans, animals, and ecosystems become more intertwined, causing a need for widely integrated governance systems. The self-called “Quadripartite of One Health,” consisting of the World Health Organization (WHO), the Food and Agriculture Organization of the United Nations (FAO), the United Nations Environment Programme (UNEP), and the World Organization for Animal Health (WOAH, former OIE) represents a unique collaboration in a situation of regime complexity and global health threats. These cooperative structures that evolved along the COVID-19 pandemic were scrutinized by analyzing semi-structured interviews with 10 employees of the organizations and 15 official documents of the four institutions using a tailor-made analysis framework derived from three selected dimensions of regime complexity: competition, legal inconsistencies, and fragmented accountability. Regime complexity is likely causing negative as well as positive effects on the Quadripartite collaboration, confirming some of the selected arguments of regime complexity literature. It was found that despite their efforts to make use of the positive effects that regime complexity brings about, like data-sharing, exchange of expertise, and increased innovation, several negative effects like discrepancies in terms of rules, procedures, human and financial resources, and understandings of mandates, as well as competition and protectionism, were observed.
