Infectious immunology is the interaction between infections and the host response towards these. When we are exposed to infections, we need an effective defense system - the immune system - to fight these infections. Infection immunology tries to describe the mechanisms of the immune system that have implications for the discovery and handling of the infection and how the micro-organism tries to avoid this effect. Experimentally this is through the use of model systems such as infections in animal models.
To help the immune system we can vaccinate the host against the components of the micro-organism that the immune system normally recognizes. It is therefore important to know exactly which parts of the micro-organism is being recognized by different parts of the immune system, and to understand what is required, to obtain an optimal immune response so that we can design the best possible vaccines.