(a,b): Levels of antibody titers in CKD patients, HD patients, and KTR. (a) shows the results of the Abbott SARS-CoV-2 IgG II Quant Assay test (median, 25, and 75% percentile for CKD: 230.3 (48.3–497.6), for HD: 151.6 (47.7–458.4), for KTR: 4.8 (3.0–30.2); (b) shows the results of the Liaison® SARS-CoV-2 S1/S2 IgG test (median, 25, and 75% percentile for CKD: 602.0 (252.5–800.0), for HD: 121.5 (32.0–293.0), for KTR: 10.3 (1.9–74.3). Logarithmic scale. Circles represent statistical outliers between 1.5 to 3.0 times of the interquartile range (IQR), asterisks represent statistical outliers more than 3 times of the IQR.