Table 2.
Seropositivity rates and neutralization antibody levels in 76 healthcare workers at 2, 4 and 6 months since onset of symptoms
| Time of follow-up (months) | Time of follow-upSARS-CoV-2 strain/variant | Number of samples | Non detectable n (%) | Positive n (%) | NAb titer 1:10–1:40 n (%) | NAb titer 1:80–1:320 n (%) | NAb titer ≥ 1:640 n (%) | Median (IQR)a | GMT value (95% CI)a |
|---|---|---|---|---|---|---|---|---|---|
| 2 | D614G | 76 | 26 (34.2) | 50 (65.8) | 36 (47.4) | 13 (17.1) | 1 (1.3) | 10.0 (5.0–40.0) | 16.5 (12.6–21.7) |
| Delta | 76 | 56 (73.7) | 20 (26.3) | 19 (25.0) | 1 (1.3) | 0 (0.0) | 5.0 (5.0–10.0) | 6.4 (5.7–7.2) | |
| Gamma | 76 | 61 (80.3) | 15 (19.7) | 15 (19.7) | 0 (0.0) | 0 (0.0) | 5.0 (5.0–5.0) | 5.9 (5.4–6.4) | |
| Mu | 76 | 70 (92.1) | 6 (7.9) | 6 (7.9) | 0 (0.0) | 0 (0.0) | 5.0 (5.0–5.0) | 5.3 (5.1–5.5) | |
| Omicron | 76 | 73 (96.0) | 3 (4.0) | 3 (4.0) | 0 (0.0) | 0 (0.0) | 5.0 (5.0–5.0) | 5.1 (5.0–5.3) | |
| 4 | D614G | 76 | 26 (34.2) | 50 (65.8) | 42 (55.3) | 7 (9.2) | 1 (1.3) | 10.0 (5.0–40.0) | 14.9 (11.4–19.5) |
| Delta | 76 | 39 (51.3) | 37 (48.7) | 36 (47.4) | 1 (1.3) | 0 (0.0) | 5.0 (5.0–10.0) | 8.2 (7.1–9.5) | |
| Gamma | 76 | 51 (67.1) | 25 (32.9) | 25 (32.9) | 0 (0.0) | 0 (0.0) | 5.0 (5.0–5.0) | 6.5 (5.9–7.2) | |
| Mu | 76 | 61 (80.3) | 15 (19.7) | 15 (19.7) | 0 (0.0) | 0 (0.0) | 5.0 (5.0–5.0) | 5.7 (5.4–6.1) | |
| Omicron | 76 | 69 (90.8) | 7 (9.2) | 7 (9.2) | 0 (0.0) | 0 (0.0) | 5.0 (5.0–5.0) | 5.4 (5.1–5.7) | |
| 6 | D614G | 76 | 6 (7.9) | 70 (92.1) | 37 (48.7) | 26 (34.2) | 7 (9.2) | 40.0 (20.0–160.0) | 48.0 (34.0–67.8) |
| Delta | 76 | 26 (34.2) | 50 (65.8) | 40 (52.6) | 10 (13.2) | 0 (0.0) | 10.0 (5.0–20.0) | 14.1 (10.9–18.3) | |
| Gamma | 76 | 36 (47.4) | 40 (52.6) | 39 (51.3) | 1 (1.3) | 0 (0.0) | 10.0 (5.0–10.0) | 8.3 (7.3–9.5) | |
| Mu | 76 | 42 (55.3) | 34 (44.7) | 34 (44.7) | 0 (0.0) | 0 (0.0) | 5.0 (5.0–10.0) | 7.5 (6.6–8.4) | |
| Omicron | 76 | 64 (84.2) | 12 (15.8) | 12 (15.8) | 0 (0.0) | 0 (0.0) | 5.0 (5.0–5.0) | 5.8 (5.3–6.5) |
NAb Titer neutralizing antibodies titer
aNon detectable results were assigned a value of 5.0