Immune milestones associated with control of clinically significant CMV reactivation. Over time (x-axis) allo-HSCT recipients before day +100 had control of clinically significant CMV infection while on letermovir (blue bar). After discontinuation of letermovir prophylaxis on day +100 those with clinically significant CMV infection (virus level depicted as above the level of detection) had lower CD4⁺ (purple) and CD8⁺ (green) CMV–specific T cells and lower memory-like NK cells (pink).