T-cell function analysis in patients with CLL after multiple vaccination doses. The IFN-γ and IL-2 responses were tested against the Miltenyi spike peptide pool. The mean number of responding cells in negative controls were subtracted from stimulated samples to account for background responses and results were expressed as spot-forming units (SFU) per 10⁶ cells. The positivity threshold (dotted line) was set based on the average number of responding cells across all negative controls in the cohort plus 3× the standard deviation. Median (red) and 95% confidence intervals were plotted for each antispike protein antibody level strata.