IL9 and infection: The divergence we describe in the immune response post-infection, compared to vaccination, is not unprecedented; Mycobacterium tuberculosis infection results in high levels of mycobacteria-specific IL-17 [37] and IL-9 [38] produced by T cells, whereas in recent clinical trials of the MVA85A vaccine, only extremely high doses induced a significant increase in IL-17 production, despite prior BCG vaccination [39].