Table 2.
Geometric Mean Concentrations for Anti-SARS-CoV-2 RBD and N Antigens by COVID-19 Case Status, COVID-19 Vaccination Status, and Laboratory-Confirmed Prior SARS-CoV-2 Infection
| Spike Protein RBD | N Protein | |||||||
|---|---|---|---|---|---|---|---|---|
| Test-Negative Control | SARS-CoV-2 Case | Test-Negative Control | SARS-CoV-2 Case | |||||
| Variable | Antibody Response a / Tested, No. (%) | Geometric Mean Concentration (95% CI) | Antibody Response a / Tested, No. (%) | Geometric Mean Concentration (95% CI) | Antibody Response b / Tested, No. (%) | Geometric Mean Concentration (95% CI) | Antibody Response b / Tested, No. (%) | Geometric Mean Concentration (95% CI) |
| Delta period | 381/416 (92) | 497.8 (398.6–621.6) | 63/87 (72) | 112.1 (57.9–217.2) | 148/416 (36) | 4.0 (3.3–4.8) | 17/87 (20) | 2.1 (1.5–3.0) |
| COVID-19 vaccination status | ||||||||
| Unvaccinated | 58/82 (71) | 67.7 (35.3–130.1) | 5/28 (18) | 3.1 (1.3–7.4) | 33/82 (41) | 5.3 (3.0–9.4) | 4/28 (14) | 1.2 (.7–2.1) |
| 2 doses | 226/234 (97) | 494.1 (395.5–616.7) | 45/45 (100) | 468.3 (319.2–687.1) | 63/234 (27) | 2.8 (2.2–3.5) | 7/45 (16) | 2.1 (1.2–3.6) |
| 3 doses | 97/100 (97) | 2600.4 (1960.9–3448.6) | 13/14 (93) | 1522.0 (411.0–5635.9) | 52/100 (52) | 7.1 (5.8–8.9) | 6/14 (43) | 7.0 (3.3–15.0) |
| 4 doses | … | … | … | … | … | … | … | … |
| Time since last COVID-19 vaccination, d | ||||||||
| <90 | 103/105 (98) | 2800.3 (2244.1–3494.4) | 15/16 (94) | 1463.9 (474.1–4519.8) | 56/105 (53) | 7.3 (5.9–9.1) | 7/16 (44) | 7.5 (3.3–17.1) |
| ≥90 | 220/229 (96) | 460.6 (365.9–579.9) | 43/43 (100) | 449.8 (302.4–669.0) | 59/229 (26) | 2.7 (2.2–3.4) | 6/43 (14) | 1.9 (1.1–3.3) |
| Evidence of prior SARS-CoV-2 infection | ||||||||
| Yes | 154/154 (100) | 1903.7 (1560.3–2322.6) | 16/17 (94) | 1093.8 (359.2–3330.4) | … | … | … | … |
| No | 227/262 (87) | 226.3 (168.6–303.7) | 47/70 (67) | 64.5 (31.1–133.5) | … | … | … | … |
| Omicron period | 886/940 (94) | 1189.0 (1049.7–1346.8) | 530/575 (92) | 822.7 (689.9–981.1) | 580/940 (62) | 15.5 (13.6–17.8) | 228/575 (40) | 5.7 (5.0–6.5) |
| COVID-19 vaccination status | ||||||||
| Unvaccinated | 115/160 (72) | 115.8 (74.0–181.2) | 50/85 (59) | 41.8 (21.8–80.3) | 106/160 (66) | 29.5 (19.0–45.9) | 38/85 (45) | 6.2 (3.8–10.2) |
| 2 doses | 231/233 (99) | 1323.6 (1115.3–1570.8) | 143/150 (95) | 522.5 (394.0–693.0) | 141/233 (61) | 17.4 (12.9–23.4) | 39/150 (26) | 3.2 (2.4–4.2) |
| 3 doses | 514/521 (99) | 2192.0 (1977.2–2427.8) | 323/326 (99) | 2078.0 (1860.3–2321.1) | 316/521 (61) | 12.3 (10.6–14.3) | 142/326 (44) | 7.0 (6.0–8.1) |
| 4 doses | 26/26 (100) | 3658.7 (3112.4–4301.0) | 14/14 (100) | 3250.3 (2389.2–4421.9) | 17/26 (65) | 11.3 (7.8–16.4) | 9/14 (64) | 14.7 (5.9–36.8) |
| Time since last COVID-19 vaccination, d | ||||||||
| <90 | 198/202 (98) | 2760.8 (2345.4–3249.8) | 89/91 (98) | 2660.4 (2020.3–3503.2) | 149/202 (74) | 17.0 (13.6–21.1) | 56/91 (62) | 10.6 (8.0–14.2) |
| ≥90 | 573/578 (99) | 1687.8 (1524.9–1868.1) | 391/399 (98) | 1187.4 (1033.1–1364.7)) | 325/578 (56) | 12.6 (10.7–14.8) | 134/399 (34) | 4.9 (4.2–5.7) |
| Evidence of prior SARS-CoV-2 infectionc | ||||||||
| Yes | 577/595 (97) | 1976.5 (1756.0–2224.8) | 233/242 (96) | 1689.0 (1363.2–2092.6) | … | … | … | … |
| No | 309/345 (90) | 494.9 (387.0–632.9) | 297/333 (89) | 487.8 (381.0–624.6) | … | … | … | … |
Geometric mean concentrations are presented as BAU/mL.
Abbreviations: bAb, binding antibody; BAU, binding antibody units; N, nucleocapsid; RBD, receptor-binding domain.
aTetracore cutoff (anti-RBD BAU/mL) = 15.9.
bTetracore cutoff (anti-N BAU/mL) = 6.9.
cEvidence 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. A total of 253 individuals had electronic medical record documentation of prior positive SARS-CoV-2 test results. Anti-N bAb–level measurements are not shown for this variable because anti-N bAb levels were included in the calculation of prior infection.