In chronic SIV infection, estimates of total CD8+ T cell efficiency derived from CD8+ depletion experiments (median 0.3–0.4 d−1[19]) and from modelling longitudinal data using the approach of Regoes et al. [20] (median 0.76 d−1[21]) are similar to estimates from modelling SIV escape in chronic infection (approximately 0.8 d−1) [22], [23], lending credence to the quantification of efficiency from viral escape. This evidence concerns the gene CD8A and infection.