Table 2. The duration and changes in total antibody levels against the SARS-CoV-2 spike protein measured with Index value three to five months (T1) and 10 to 12 months (T2) after PCR test for PCR positive (PCR+) and PCR negative (PCR-) participants.
| Time point to antibody measurement | Antibody level category in Index value | Total | PCR+ | PCR- |
|---|---|---|---|---|
| N (%) | N (%) | N (%) | ||
| T1 antibody | 0.00–0.79 | 718 (65.0) | 25 (6.4) | 693 (98.7) |
| T1 antibody | 0.80–1.99 | 27 (2.5) | 26 (6.6) | 1 (0.1) |
| T1 antibody | 2.00–9.99 | 135 (12.3) | 132 (33.8) | 3 (0.4) |
| T1 antibody | ≥10 | 213 (19.5) | 208 (53.2) | 5 (0.7) |
| T2 antibody | 0.00–0.79 | 8 (3.8) | ||
| T2 antibody | 0.80–1.99 | 14 (6.6) | ||
| T2 antibody | 2.00–9.99 | 63 (29.7) | ||
| T2 antibody | ≥10 | 127 (59.9) | ||
| Decreased antibody level, T1 to T2 | 39 (18.4) | |||
| Unchanged antibody level, T1 to T2 | 35 (16.5) | 2a | ||
| Increased antibody level, T1 to T2 | 25 (11.8) | 1a | ||
| Antibody level ≥ 10 at T1 & T2 | 113 (53.3) |
a Percent is not reported due to low number of participants with antibodies in this group.