Compared to serum IgG antibody, smaller proportions of patients had IgA antibody to each of the HCoV strains in nasal wash specimens (12 [11%] were HCoV-229E positive, 8 [8%] were HCoV-NL63 positive, 22 [22%] were HCoV-OC43 positive, and 31 [31%] were HCoV-HKU1 positive) (P Ͻ 0.0001) ( Table 2 ).