Table 3.
Comparison of COVID-19 antibody response between those with or without pre-existing anti-spike antibody before vaccination in overall cohort (n = 135).
| Anti-COVID Antibody | COVID-19 Antibody | Time of Specimen Collection (Days) | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Before Second Dose at 28 Days | 60 Days after Second Dose | 150 Days after Second Dose | 270 Days after Second Dose | ||||||
| Anti-Spike antibody (U/mL) | Anti-spike antibody was absent before vaccination (n = 99) | 40.9 (11.8–118.3) |
p < 0.001 | 234.3 (96.3–9268) |
p = 0.007 | 102.6 (41.4–1837) |
p < 0.001 | 1858 (215.8–6784) |
p = 0.333 |
| Anti-spike antibody was present before vaccination (n = 36) | 5929.5 (649.4–16,207.5) |
3395 (800.1–8852) |
1805 (201.9–4131) |
2423.5 (707.1–9552) |
|||||
| Neutralising antibody (%) | Anti-spike antibody was absent before vaccination (n = 99) | 18.3 (5.9–32) |
p < 0.001 | 36.6 (7.4–91.9) |
p = 0.255 | 26.7 (3.6–85.5) |
p = 0.155 | 63.4 (17.6–85.4) |
p = 0.626 |
| Anti-spike antibody was present before vaccination (n = 36) | 80 (24.1–95.8) |
69.9 (12.6–94.2) |
62.1 (13.2–89) |
53.6 (17–84.1) |
|||||
Anti-spike antibody titre is expressed as U/mL and neutralising antibody is expressed in percentage. The anti-spike antibody titre value ≥ 0.80 U/mL is considered positive. The specimens with calculated neutralisation ≥ 20% are considered positive for neutralising antibody. Data are expressed as median (interquartile range).