Over the millennium, M. tuberculosis complex strains have branched into several lineages and genotypic variations can determine the virulence and transmissibility of clinical M. tuberculosis (Mtb). However, the mechanism behind the variability in transmission of Mtb remains elusive. Therefore, we investigated understanding the pathogenesis and vaccine efficacy between the high, moderate and low transmission Mtb in mice. The study used three Mtb strains based on their transmission within the Kenyan population – high, moderate and low. The project focused on the characterisation of Mtb strains isolated from Kenyan individuals, BCG vaccine efficacy and pathological analysis in mice against Mtb strains.