Fig. 4: Total HA binding antibody and HA stalk antibody responses measured by ELISA at pre-vaccination (Day 0), 1-month, and 6-months post-vaccination in Year 1.

Antibody titers from each of the four vaccine groups were presented as geometric mean titers (GMTs) with 95% confidence interval (CI) for combined 18−44 years and 45−64 years age groups. Gray dots represented individual titers. Fluzone IIV4: Day 0 (n = 24), 1 m (n = 24), 6 m (n = 21); Fluarix IIV4: Day 0 (n = 24), 1 m (n = 24), 6 m (n = 23); ccIIV4: Day 0 (n = 56), 1 m (n = 54), 6 m (n = 51); RIV4: Day 0 (n = 40), 1 m (n = 40), 6 m (n = 38). A: HA (A(H1N1)pdm09) or HA head (A(H3N2), B/VIC, B/YAM) binding antibodies. B: Ratios of egg/cell HA or HA head binding antibody titers with 95% CI. C: H3 stalk and H1 stalk antibody responses at day 0, 1-month and 6-months post vaccination. D: Fold rise of H3 stalk and H1 stalk antibody titers from pre to 1-month post-vaccination with 95% CI. One-way ANOVA corrected for multiple comparisons (Tukey’s test) was used to compare the GMTs of each time point among the 4 vaccine groups (A, C). One-way ANOVA nonparametric Kruskal-Wallis test was used to compare the fold changes among the 4 vaccine groups (B, D). Statistically significant differences between groups are indicated by p values on the horizontal bars.*: In (C), paired t test (two-tailed) was used for comparing the pre- and 1 m post-vaccination stalk antibody titers within the same vaccine group: significantly higher HA stalk antibody titers were detected in 1 m post-vaccination than pre-vaccination for H3 stalk binding antibody in Fluzone IIV4 (p = 0.0009), ccIIV4 (p = 0.0004), RIV4 (p < 0.0001); and for H1 stalk binding antibody in Fluzone IIV4 (p = 0.0005), Fluarix IIV4 (p = 0.0092), ccIIV4 (p < 0.0001), RIV4 (p = 0.0015).