A retrospective analysis of 112 Mauritian cynomolgus macaques from different preclinical trials, vaccinated (n = 67) or not (n = 45) with Tat and challenged with the SHIV-89.6P, showed that vaccination induced a significant reduction of the rate of infection acquisition at 10 MID50 (P < 0.0001), and contained acute CD4+ T cell loss at 15 MID50 (P = 0.0099). This evidence concerns the gene CD4 and infection.