Tuberculosis (TB) infection can enter an asymptomatic 'latent' phase and re-emerge later. The only approved TB vaccine, BCG, targets just the disease's early, active stage. A vaccine candidate, H56, that contains an antigen from the latent phase affords mice longer-lasting protection against the disease than does BCG, report Claus Aagaard and Peter Andersen at the Statens Serum Institute in Copenhagen and their co-workers.

The H56 vaccine contains three antigens, including one, Rv2660c, that is expressed during TB's latent stage. When given to mice before infection, H56 generated more diverse T-cell responses than the BCG vaccine, and also yielded a lower bacterial load by 24 weeks post-infection. When administered after the mice had been infected and treated with antibiotics, H56 protected the animals against developing reactivated infections. The team hopes to test the vaccine in humans.

Nature Med. doi:10.1038/nm.2285 (2011)