Antibody conversion rates to SARS-CoV-2 in saliva from children attending summer schools in Barcelona, Spain

Table 2 Saliva antibody conversion rates between the first and last study visit

Antibody	Antigen	Increased^a N (%)			Decreased^b N (%)			Maintained^c N (%)
Fold change:		< 4	≥4	Total	< 4	≥4	Total	-
IgM	N CT^d	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

ISSN: 1741-7015