ID91+EmT4™ vaccination provides prophylactic protection against M.tb HN878 in both young and aged Beige mice. (A) The 4 M.tb proteins comprising the ID91 antigen, and immunizations received by each group. (B) Timeline of immunizations and aerosol M.tb HN878 challenge. Experimental samples were collected at D70 (4 wk post M.tb HN878 challenge). Bacterial burden in (C) lung and (D) spleen organ homogenates of young (6 to 8 wk) and aged (20 mo) Beige mice immunized with either saline (circles) or ID91+EmT4 (squares and grey bar) post M.tb HN878 challenge. Bars show mean ± SEM, dots represent individual mice, n = 6-7/group. Asterisks indicate statistical significance compared to the saline group, where *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001 using 1-way ANOVA with Dunnett’s multiple comparisons test. Data representative of 1 experiment.