Figure 3.

Correaltion between netralizing antibody titers and HA‐specific antibody titers. (a,b) Correlation between increased serum neutralizing antibody titers and serum (a) IgG or (b) IgA titers (n = 49). Serum neutralizing antibody titers showed a weak positive correlation with serum IgG titers (Spearman r = 0.398; P = 0.0046). (c,d) Correlation between increased nasal neutralizing antibody titers and nasal (c) IgG or (d) IgA titers (n = 49). Titers were measured on day 0 (before vaccination) and day 301. Nasal neutralizing antibody titers strongly correlated with nasal IgA titers (Spearman r = 0.742; P < 0.0001) but not with nasal IgG titers