In this chapter Mar Pérezts, Xavier Philippe, Sébastien Picard and Véronique Steyer offer a broad vision of corporate political activities, highlighting its institutional reach, and describing its concrete institutionalizing effects. Drawing on Lallement (2008) the authors attempt at opening the black box of the institutionalization processes of corporate political activities and the institutional dynamics associated to this type of activities. Using data from an in-depth ethnography in VaxCorp, a leading corporation in the vaccine industry, the authors analyse how the company shapes its institutional field by imposing the dominant ‘vaccinology’ imaginary. In practice this takes shape in a modus operandi that goes beyond the mere maximization of VaxCorp’s interests to organize actions and behaviours of other institutional actors (for example, State, WHO). The analysis indicates that this dominant imaginary emerges from but also intertwines institutionalizing processes into a larger and coherent pattern, which eventually legitimizes corporations’ dominance in an institutional field.