2.8. Statistical analysis

Data and statistical analyses were performed by using the Prism software (version 7.03, GraphPad, La Jolla, CA, USA). IgG titer and OI were expressed as geometric mean and 95% confidence interval (GMT±95% C.I.). Differences in IgG or OPA titers between immunization groups were assessed after logarithmic transformation of data, two-way ANOVA analysis of variance and Sidak's multiple comparison tests. Avidity data were expressed as the median with interquartile range (IQR). Independent sample Mann–Whitney U test was used to assess differences in AI values between vaccine groups, and one-sample t test analysis was performed to classify serotypes as low (<40%) or high (>60%) avidity. ELISPOT data were expressed as mean ± standard error of mean (S.E.M.), and datasets analyzed by One-Way or Two-Way ANOVA followed by multiple comparisons as described in Figure legends. Differences were considered significant at p values < 0.05 and were indicated as follows: ∗p < 0.05, ∗∗p < 0.01,∗∗∗p < 0.001 and ∗∗∗∗p < 0.0001; ns, not significant.