Biological processes operate through an intricate and elaborate network of molecules. Systems biology approaches provide a comprehensive way of dissecting the complex interactions within these processes, and can lead to a better understanding of biological systems. In recent years, systems biology has been successfully applied in analyzing the immune response to a wide range of vaccines and infectious agents. This seminar highlights the recent technological and methodological advances in the field and shows how systems biology can be applied to unraveling novel insights into the molecular mechanisms of immunity.