FIG 3.

H5N1 vaccination elicits a weak antibody response against NA in humans. (A) Titers of antibody against homologous N1 (A/Vietnam/1203/2004 [VN]) and heterologous N1 (A/California/04/2009 [Cal09]) were measured on day 0 and day 42 postpriming. Titers of antibody against VN N1 increased slightly, from 1:755 to 1:1,131 (P = 0.0031), but the increase for Cal09 N1 from 1:1,817 to 1:2,072 was not significant (P = 0.7231). (B) Induction over baseline of antibodies against homologous N1 (VN) and heterologous N1 (Cal09) was calculated for day 42 postpriming. The induction for VN N1 was 1.5-fold over baseline, while induction for Cal09 N1 was only 1.1-fold.