Historically, immunization has been designed to prevent the onset of infectious disease, with vaccines acting as prophylactic agents. However, over the course of time immunization has evolved to include a therapeutic objective whereby individuals who have already contracted an infectious or neoplastic disease, and where traditional treatment options are limited, are vaccinated. With diseases such as HIV and tuberculosis the limited success of traditional chemotherapeutic and prophylactic approaches has resulted in the experimental advancement of therapeutic genetic immunization, where the host immune system is to be modulated to improve disease prognosis or ultimately, eradicate the infection. Furthermore, for cancer, a major non-infectious disease, similar experimental treatments are underway. Here we will explore how genetic immunization enables re-direction of the host immune system resulting in the development of effective immune responses