Table 5.

Changes in the seroprevalence between day 0 and 6 months.

Test	Ratio	p-value (against day 0)	Neg → pos (%neg)	Pos → neg (%pos)	Difference of prevalence (%)
S1-specific IgG	1.56	0.212	2.0	55.2	0.7
S1-specific IgA	0.33	<0.001	2.6	70.8	−4.8
RBD-specific IgM	2.88	0.012	1.8	53.3	1.2
RBD-specific total antibodies	>54	<0.001	2.1	0.0	2.1
NCP-specific IgG	3.00	0.014	1.6	50.0	1.1

Changes are indicated by the ratio of newly positives to those that became negative; and the proportion of negatives that became positive (neg → pos) as well as the proportion of positives that became negative (pos → neg) and difference of prevalences of positives at month 6 and day 0; p-value assessed by Chi² McNemar. S1 subunit of spike protein (S1), receptor-binding domain (RBD), nucleocapsid (NCP).