Table 5.
Thresholds of pre-existent IgG anti-S antibodies and neutralizing antibodies and estimates of protection against reinfection with Omicron-related variants.
| Total | Reinfection, n (%) | Risk ratio (95% confidence interval) | P-value | Risk reduction | |
|---|---|---|---|---|---|
| Total | 82 | 28 | - | - | - |
| Anti-S antibodies | |||||
| <800 BAU/ml | 54 | 23 (42.6%) | Reference | 0.029 | 58% (2%-82%) |
| ≥800 BAU/ml | 28 | 5 (17.9%) | 0.42 (0.18-0.98) | ||
| Neutralizing antibodies to Wuhan strains | |||||
| <500 IU/ml | 40 | 19 (47.5%) | Reference | 0.035 | 50% (4%-74%) |
| ≥500 IU /ml | 38 | 9 (23.7%) | 0.50 (0.26-0.96) | ||
BAU, binding arbitrary unit; Ig, immunoglobulin; S, spike.