Figure 2
Distributions of calibrated ID50 (Panel A) and ID80 (Panel B) titers of vaccine recipient samples collected at Day 29 and Day 57, estimated by the three calibration approaches. In Approach 1, titers from each lab are calibrated to the WHO International Standard using the arithmetic mean-based calibration factor, expressed in International Units (IU50/ml for ID50; IU80/ml for ID80); in Approach 2, titers from each lab are calibrated to a common scale using an independent pool of clinical samples, assuming a bivariate normal distribution for the readouts from the two labs; in Approach 3, titers from the non-reference lab (Duke) calibrated to the reference lab (Monogram) using an independent pool of clinical samples, based on regressing titers from the reference lab on the non-reference lab. Circle-shape points indicate pre-calibration titers > LLoD; triangle-shape points indicate pre-calibration titers ≤ LLoD.
