 There is a plausible rationale that BCG, a replicating mycobacterium, is capable of inducing non-specific innate immunity, which could induce protection against disease and death from non-mycobacterial infections early in life. For example, intravesical BCG is an effective treatment for bladder cancer, an effect presumed to be non-specific and innate. However, our understanding of the immunological mechanisms involved is incomplete. Data is needed from robust experiments to quantify any causal relationship between infant survival and BCG vaccination. Demonstrating an effect of recent BCG vaccination on the growth of common bacterial pathogens involved in neonatal sepsis, using whole blood in an in-vitro human model, would provide evidence to support a randomised controlled trial in infants in TB high burden countries and would impact on public health vaccination scheduling. In addition it would provide us with an in-vitro model by which to assess future BCG replacement vaccines. 