Table 2.

Seroprevalence of IgG antibodies against HCoV S1 in 140 children at ages of 1, 2, and 3 years.

	Age	Seropositivity		Cumulative seropositivity		Antibody level in seropositive (EIA units)		Reinfection rate
		n	%	n	%	GMAL ± SD	CI 95%	n	%
229E	1y	20	14	20	14	43 ± 2.1	30–61	–	–
	2y	44	31	45	32	46 ± 2.0	37–57	5	25
	3y	52	37	53	38	45 ± 2.0	37–55	11	24
HKU1	1y	29	21	29	21	41 ± 2.1	31–55	–	–
	2y	69	49	73	52	44 ± 1.9	37–51	4	14
	3y	83	59	93	66	33 ± 2.0	29–39	6	8
NL63	1y	34	24	34	24	54 ± 1.6	45–64	–	–
	2y	63	45	64	46	55 ± 1.5	49–61	7	21
	3y	107	76	108	77	54 ± 1.5	50–59	11	17
OC43	1y	43	31	43	31	39 ± 1.8	32–47	–	–
	2y	76	54	79	56	42 ± 1.8	37–48	14	33
	3y	114	81	114	81	38 ± 1.8	34–42	15	19
Any HCoV	1y	88	63	88	63	44 ± 1.9	39–49	–	–
	2y	119	85	120	86	46 ± 1.8	43–49	27	31
	3y	137	98	137	98	42 ± 1.9	39–45	40	34

The table presents the seroprevalence and cumulative seroprevalence in numbers (n) and percentages (%) of positive individuals in each age group. The geometric mean titers (GMT) and standard deviations (SD) of positive samples, and the rate of reinfection in previously seropositive children (defined as an increase of > 20 EIA units in sequential samples) are shown.

y, year of age; Seropositive defined as antibody level of > 9.5 EIA units in the sample; n, number of positive samples; GMAL, geometric mean antibody level; SD, geometric standard deviation; CI 95%, 95% confidence interval.