Our findings on the apparent ability of Advax3 to directly engage CD8+ T cells in mediating antifungal vaccine protection even in the absence of CD4+ T cells could have important implications for successful immunization of patients with compromised CD4+ T-cell immunity who are vulnerable to fungal and other microbial infections, including bacterial pneumonia, in which an unexpected role for CD8+ T cells (26) and a dispensable role for CD4+ T cells (27) have been described. Here, CD4 is linked to bacterial pneumonia.