After two years of global pandemic, it is no surprise that immunization is now at the centre of our experience. From the medicalization of politics to the disciplining of individuals, from lockdowns to mass vaccination programmes, contemporary societies now seem to be firmly embedded in a syndrome of immunity. To understand the ambivalent effects of this development, it is necessary to go back to its modern genesis, when the languages of law, politics and medicine begin to merge into the biopolitical regime under which we have been living for some time. This regime places a high priority on immunization and security: no security is more important than health security. The covid-19 pandemic has taken this dynamic to a new level: for the first time in history, we see societies seeking to achieve generalized immunity of the entire world population through vaccination, allowing us to glimpse the possibility of a 'common immunity' that strengthens the relation between community and immunity. The dramatic tensions we have experienced in recent years between security and freedom, norm and exception, power and existence, all refer to the complex relationship between community and immunity, the decisive features of which are reconstructed in this book. Building on the prescient argument originally developed two decades ago in Immunitas, Roberto Esposito demonstrates in this new book how the pandemic and our responses to it have brought into sharp relief the fundamental biopolitical conditions of our contemporary societies.