Table 2.
Saliva antibody conversion rates between the first and last study visit
| Antibody | Antigen | Increaseda N (%) |
Decreasedb N (%) |
Maintainedc N (%) |
||||
|---|---|---|---|---|---|---|---|---|
| Fold change: | < 4 | ≥4 | Total | < 4 | ≥4 | Total | - | |
| IgM | N CTd | 207 (13.6%) | 0 (0%) | 207 | 245 (16.1%) | 0 (0%) | 245 | 1066 (70.2%) |
| N FL | 241 (15.9%) | 1 (0.06%) | 242 | 344 (22.6%) | 1 (0.06%) | 345 | 931 (61.3%) | |
| RBD | 192 (12.6%) | 0 (0%) | 192 | 212 (13.9%) | 0 (0%) | 212 | 1114 (73.4%) | |
| S | 223 (14.7%) | 0 (0%) | 223 | 243 (16.0%) | 0 (0%) | 243 | 1052 (69.3%) | |
| S2 | 268 (17.6%) | 2 (0.1%) | 270 | 340 (22.4%) | 2 (0.13%) | 342 | 906 (59.7%) | |
| Global | 3 (0.2%) | 0 (0.0%) | - | |||||
| N FL only | 1 (0.1%) | - | - | |||||
| IgA | N CT | 524 (34.5%) | 20 (1.3%) | 544 | 619 (40.8%) | 27 (1.7%) | 646 | 328 (21.6%) |
| N FL | 546 (35.9%) | 15 (1.0%) | 561 | 656 (43.2%) | 26 (1.7%) | 682 | 275 (18.1%) | |
| RBD | 461 (30.4%) | 5 (0.3%) | 466 | 551 (36.3%) | 7 (0.4%) | 558 | 494 (32.5%) | |
| S | 442 (29.1%) | 3 (0.2%) | 445 | 529 (34.8%) | 6 (0.4%) | 535 | 538 (35.4%) | |
| S2 | 481 (31.7% | 8 (0.5%) | 489 | 627 (41.3%) | 19 (1.2%) | 646 | 383 (25.2%) | |
| Global | 36 (2.3%) | 1 (0.1%) | - | |||||
| N FL only | 8 (0.5%) | - | - | |||||
| IgG | N CT | 566 (37.3%) | 14 (0.9%) | 580 | 509 (33.5%) | 14 (1.0%) | 523 | 415 (27.3%) |
| N FL | 586 (38.6%) | 15 (1.0%) | 601 | 561 (36.9%) | 18 (1.3%) | 579 | 338 (22.3%) | |
| RBD | 439 (28.9% | 2 (0.1%) | 441 | 419 (27.6%) | 5 (0.3%) | 424 | 653 (43.0%) | |
| S | 418 (27.5%) | 3 (0.2%) | 421 | 376 (24.8%) | 5 (0.3%) | 381 | 716 (47.2%) | |
| S2 | 504 (33.2%) | 6 (0.4%) | 510 | 500 (32.9%) | 12 (0.8%) | 512 | 496 (32.7%) | |
| Global | 26 (1.7%) | 4 (0.3%) | - | |||||
| N FL only | 9 (0.6%) | - | ||||||
| Total | 49 (3.2%) | 0 (0.0%) | - | |||||
| N FL only | 13 (0.9%) | - | - | |||||
aThe number (N) of subjects who increased antibody levels was calculated for each isotype/antigen pair, per Ig isotype, and globally, out of the 1518 individuals in whom two samples were available with ≥6 days of difference (see also Fig. 1). Individuals who increased antibody levels ≥4-fold change (FC) for at least one isotype/antigen were considered antibody positive. The total saliva antibody conversion rate (% in bold) was calculated as the proportion of positive individuals
bA decrease in antibody levels ≥4 FC was interpreted as negativization for any given isotype/antigen pair. Within an individual, complete antibody reversion was considered only if the antibody levels decreased ≥4 FC for all the isotype/antigen pairs
cIndividuals who maintained antibody levels between visits are computed for comparison
dN nucleocapsid, CT C-terminus end, FL full-length, RBD receptor binding domain of spike (S). Antibody conversion for N FL is shown separately as representative of potential cross-reactivity with endemic human coronaviruses