HCT outcome according to Flu exposure. Adjusted Kaplan-Meier plots and cumulative incidence plots of EFS (A), OS (B), NRM (C), graft failure (D), relapse (E), and immune reconstitution (F). Patients are stratified for within optimal exposure (optimum 25%), above optimal exposure, and below optimal exposure. P values are derived from the Wald test in the full regression models. ^aAdjusted for age (polynomial spline, 3 degrees of freedom), indication (lymphoma/leukemia, benign, myelodysplastic syndrome, plasma cell disorder), and prior allogeneic transplants (yes/no). ^bAdjusted for age (polynomial spline, 3 degrees of freedom) and prior allogeneic transplants (yes/no). ^cAdjusted for indication (malignant/benign). ^dAdjusted for age (polynomial spline, 4 degrees of freedom). *Significant at level P < .05. **Significant at level P < .01. ***Significant at level P < .001.