Recombinant MVA encoding antigen 85A MVA85A induces both a CD4+ and a CD8+ epitope when used to immunise mice. When mice are primed with BCG and then given MVA85A as a boost, the levels of CD4+ and CD8+ T cells induced are higher than with either BCG or MVA85A alone, and this regime is more protective than either vaccine alone (Goonetilleke et al, 2003). In the more sensitive guinea pig model, guinea pigs vaccinated with BCG, and then MVA85A, and then a second viral vector, fowlpox expressing antigen 85A, 6/6 guinea pigs are alive at the end of the experiment, compared with 2/6 guinea pigs vaccinated with BCG alone, and 0/6 control animals (Williams et al, 2005).