Severe Combined lmmunodeficient (SCID) Mice in Vaccine Assessment

New or improved vaccines will require testing before they are licensed for use in the general population. Although toxicity and immunological data can be obtained from phase 1 human trials, in the vast majority of cases, it is not possible to challenge vaccine recipients with the specific infectious agent in order to assess protection. Therefore, prior to large-scale production of vaccines and their assessment in phase 2 and 3 clinical trials, there is a requirement for in vivo studies that can predict the efficacy of the vaccines. Although many animal models are available for infectious disease studies, they all rely on the animal’s own immune system for the generation of the protective responses, and these may not reflect the immunological responses generated in the human. In addition, some infections are specific to humans, and it is sometimes very difficult to find suitable animal species that human pathogens will infect. This may be because of the lack of appropriate receptors, the presence of a functional immune system able to eliminate the pathogen, and the fact that models cannot always be relied on to re-create the normal pathophysiology.