CD8A and infection: Additionally, the IDR (p < 0.0001, R = −0.7815) and the frequencies of multifunctional CD4+ (p < 0.0500, R = −0.2803) and CD8+ T cells (p < 0.0001, R = −0.7837) expressing IL-2, TNF-α, and IFN-γ, after infection, were strong correlates of prophylactic efficacy.