CD8A and scrub typhus: We propose that a modern approach to vaccine development against scrub typhus will require the development of more appropriate animal models and should be guided by two general overarching principles: (1) identification of relevant antigens that, in combination, can stimulate all relevant branches of adaptive immunity, namely antibodies, CD4+ T cells, and CD8+ T cells; and (2) definition of immunological correlates of protection to guide the selection of vehicles, vectors, schedules, and adjuvants.