Table 3.
Likelihood of Symptomatic COVID-19 by Anti-N Binding Antibody Levels, COVID-19 Vaccination Status, and Prior SARS-CoV-2 Infection
| Delta Perioda | Omicron Periodb | |||||
|---|---|---|---|---|---|---|
| Variable | Cases/Total | Anti-RBD bAb ≥1968 BAU/mLc/ Controls | Anti-RBD bAb ≥1968 BAU/mLc/ Cases | Cases/Total | Anti-RBD bAb ≥3375 BAU/mLd/ Controls | Anti-RBD bAb ≥3375 BAU/mLd/ Cases (%) |
| Anti-N bAb levels | ||||||
| Low, <10 BAU/mL | 76/389 (20) | 83/313 (27) | 10/76 (13) | 402/847 (47) | 84/445 (19) | 71/402 (18) |
| Medium, 10–99 BAU/mL | 7/79 (9) | 54/72 (75) | 4/7 (57) | 133/430 (31) | 156/297 (53) | 64/133 (48) |
| High, ≥100 BAU/mL | 4/35 (11) | 19/31 (61) | 2/4 (50) | 40/238 (17) | 84/198 (42) | 16/40 (40) |
| COVID-19 vaccination status | ||||||
| Unvaccinated | 28/110 (25) | 13/82 (16) | 1/28 (4) | 85/245 (35) | 14/160 (9) | 6/85 (7) |
| 2 doses | 45/279 (16) | 56/234 (24) | 6/45 (13) | 150/383 (39) | 59/233 (25) | 14/150 (9) |
| 3 doses | 14/114 (12) | 87/100 (87) | 9/14 (64) | 326/847 (38) | 233/521 (45) | 122/326 (37) |
| 4 doses | … | … | … | 14/40 (35) | 18/26 (69) | 9/14 (64) |
| Evidence of prior SARS-CoV-2 infectione | ||||||
| No | 70/332 (21) | 50/262 (19) | 6/70 (9) | 333/678 (49) | 28/345 (8) | 41/333 (12) |
| Yes | 17/171 (10) | 106/154 (69) | 10/17 (59) | 242/837 (29) | 296/595 (50) | 110/242 (45) |
Data are presented as No. (%).
Abbreviations: bAb, binding antibody; N, nucleocapsid; RBD, receptor-binding domain.
aThe Delta-predominant period was defined as 1 October to 24 December 2021.
bThe Omicron-predominant period was defined as 25 December 2021 to 29 June 2022.
c50% reduction in odds of symptomatic COVID-19 cutoff for anti-RBD binding antibody levels during the Delta period: 1968 BAU/mL.
d50% reduction in odds of symptomatic COVID-19 cutoff for anti-RBD binding antibody levels during the Omicron period: 3375 BAU/mL.
eEvidence of prior SARS-CoV-2 infection was defined as electronic medical record documentation of prior positive SARS-CoV-2 test results or anti-N bAb levels in acute sera indicative of prior infection (≥6.9 BAU/mL). Prior infection was documented from 17 March 2020 to 12 June 2022. Anti-N bAb-level measurements are not shown for this variable because anti-N bAb levels were included in the calculation of prior infection.