Table 3.

Association between qualitative variables and sex as control variable, by stratum of age· The table shows the chi-square test used in each case to evaluate the statistical significance of the association between two categorical variables· RBD: receptor binding domain. ACE-2: angiotensin-converting enzyme.

Seroconversion of anti-RBD IgG
	12–18 years old		3–11 years old		Overall (3–18 years old)
	Yes	No	Yes	No	Yes	No
Male	105	6	119	1	224	7
Female	117	0	114	0	231	0
P value	0·03		1·00		0·02

Inhibition to RBD-ACE2 binding
	12–18 years old		3–11 years old		Overall (3–18 years old)
	Yes	No	Yes	No	Yes	No
Male	87	24	110	10	197	34
Female	105	12	110	4	215	16
P value	0·03		0·20		0·01

Viral neutralisation
	12–18 years old		3–11 years old		Overall (3–18 years old)
	Yes	No	Yes	No	Yes	No
Male	50	2	98	10	148	12
Female	56	1	107	0	163	1
P value	0·94		<0·01		<0·01

RBD: receptor binding domain; E1, 12–18 years old; E2, 3–11 years old; GMT: geometric mean titres; ACE-2: angiotensin-converting enzyme.