Table 3.
Summary of calibrated ID50 and ID80 titers from the Duke and Monogram labs and their fold-differences for Day 29 vaccinee sera and Day 57 vaccinee sera.
| Calibrated ID50 | Vaccine Day 29 (n = 27) | Vaccine Day 57 (n = 30) | ||||
|---|---|---|---|---|---|---|
| Approach 1 | Approach 2 | Approach 3 | Approach 1 | Approach 2 | Approach 3 | |
| Duke | ||||||
| Mean (SD)* | 15.9 (0.8) | 185.8 (1.0) | 284.2 (0.7) | 353.9 (1.1) | 3955.5 (1.0) | 3426.3 (0.9) |
| Median | 17.5 | 227.4 | 307.5 | 374.1 | 5030.2 | 3582.3 |
| Range | 3.1–110.3 | 22.1–1210.8 | 77.5–1344.5 | 3.6–1140.0 | 66.4–15,078.3 | 86.9–8757.2 |
| Monogram | ||||||
| Mean (SD)* | 11.6 (1.0) | 190.9 (0.8) | 178.3 (1.0) | 268.9 (1.0) | 3911.0 (1.0) | 4120.7 (1.0) |
| Median | 14.3 | 210.0 | 219.5 | 344.2 | 4128.0 | 5274.0 |
| Range | 1.3–79.8 | 39.4–1257.3 | 20.0–1222.0 | 4.0–1062.5 | 45.3–12,208.5 | 62.0–16,280.0 |
| Monogram versus Duke fold difference | ||||||
| Mean (SD)* | 0.7 (0.4) | 1.0 (0.4) | 0.6 (0.5) | 0.8 (0.4) | 1.0 (0.4) | 1.2 (0.4) |
| Median | 0.7 | 1.0 | 0.7 | 0.7 | 1.0 | 1.2 |
| Range | 0.3–1.9 | 0.4–2.9 | 0.2–1.5 | 0.3–1.7 | 0.4–2.2 | 0.7–3.0 |
| Calibrated ID80 | Vaccine Day 29 (n = 27) | Vaccine Day 57 (n = 30) | ||||
|---|---|---|---|---|---|---|
| Approach 1 | Approach 2 | Approach 3 | Approach 1 | Approach 2 | Approach 3 | |
| Duke | ||||||
| Mean (SD)* | 24.4 (0.8) | 63.5 (0.8) | 125.8 (0.6) | 496.1 (0.9) | 1460.2 (1.0) | 1330.0 (0.7) |
| Median | 29.3 | 84.8 | 145.1 | 632.7 | 1680.3 | 1609.0 |
| Range | 7.5–136.6 | 21.5–390.4 | 50.0–484.7 | 7.5–1883.8 | 21.5–5538.9 | 50.0–3779.6 |
| Monogram | ||||||
| Mean (SD)* | 13.9 (0.8) | 87.9 (0.8) | 60.9 (0.8) | 347.3 (1.0) | 1636.7 (0.9) | 1522.5 (1.0) |
| Median | 18.7 | 105.0 | 82.0 | 401.1 | 2072.5 | 1758.5 |
| Range | 4.6–89.6 | 28.0–468.1 | 20.0–393.0 | 4.6–1365.0 | 28.0–5975.6 | 20.0–5984.0 |
| Monogram versus Duke fold difference | ||||||
| Mean (SD)* | 0.6 (0.5) | 1.4 (0.5) | 0.5 (0.5) | 0.7 (0.2) | 1.1 (0.2) | 1.1 (0.3) |
| Median | 0.6 | 1.3 | 0.5 | 0.7 | 1.1 | 1.2 |
| Range | 0.2–2.3 | 0.4–3.8 | 0.2–1.5 | 0.4–1.2 | 0.7–1.8 | 0.4–2.3 |
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 per ml (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.
*Geometric mean of titers or titer ratios and standard deviation of the loge-transformed titers or titer ratios.