In this study, the investigators aim to build an infrastructure for rapidly obtaining evidence for the management of patients requiring admission to an ICU during a pandemic of severe respiratory infections. Furthermore, during the inter-pandemic phase, this infrastructure will consist of a rolling adaptive clinical trial evaluating different management strategies of patients with severe CAP admitted to ICU. This ongoing trial will serve as the framework in which different aspects of ICU patient management can be rigorously and rapidly evaluated through rapid modification (adaptation) of the trial interventions based on new circumstances (e.g., a pandemic). These modifications or adaptations may include adding "pandemic" study arms (with or without predefined treatment) or changing randomization schemes.