CD4 and infection: As with other studies, we found that NK cell and monocyte recovery occurred before T‐cell and B‐cell recovery.17, 25 CD8+ T‐cells recovered earlier than CD4+ T‐cells, with the latter only reaching the reference range21 12‐month post‐alloHSCT with reversal of the CD4+/CD8+ ratio (Figure 2a, b).21 This finding is likely due to viral reactivation and more efficient peripheral homeostatic expansion of CD8+ T cells.11 As CD4+ T cells play a central role in orchestrating all immune responses, CD4+ T‐cell counts and function are critical to infection risk post‐alloHSCT.