Serum VNA titers correlate with protection against H1N1 but not H5N1 challenge.

<p>VNA titers against (<b>A</b>) A/California/07/2009 (H1N1) and (<b>C</b>) A/Hong Kong/156/97 (H5N1) were determined. Titers for mice that survive challenge (open squares) and mice that succumb to infection (closed squares) are presented separately for pre-vaccination (pre) and post-vaccination (post) sera. Assay background level is indicated with dashed line in panels A and C. Vaccine homologous H1 VNA titers are higher in post-vaccination serum (p<0.001, t-test). H5 VNA titers are detectable in some pre-vaccination samples and are higher in post-vaccination serum (p<0.001, t-test). ROC curves were calculated to assess the correlation (<b>B</b>) between H1N1 A/California/07/2009 VNA and protection against H1N1 A/Netherlands/602/2009 challenge and (<b>D</b>) between H5N1 A/Hong Kong/156/97 VNA and protection against H5N1 A/Hong Kong/156/97 challenge. H1N1 VNA correlates with protection against homologous H1N1 challenge (ROC area = 0.80, p<0.05, 95% CI 0.66–0.94). The positive correlation between H5 VNA and H5 protection does not reach statistical significance (ROC area = 0.66, 95% CI = 0.496–0.82).