Geometric mean (GM), geometric mean titer (GMT) and 95% Confidence Intervals (CIs) were calculated for immunological parameters and summarized by time after vaccination. The percentages of responders were determined by defining a priori cut-off values for each immunological parameter: for serum IgG, IgA and SBA the cut-off value was ≥4-fold rise in titer compared to baseline, for memory B cells the cut-off value was mean + 2 SD of all placebo recipients at each time point.
Differences between GMTs or GMs at follow up versus pre-vaccination and 3 months post-last injection time points were examined by the Wilcoxon signed rank test for repeated measurements. Correlations between immunological parameters were assessed using Spearman’s rank correlation coefficient. Fisher’s exact test was used to assess unadjusted associations of the frequency of specific-IgG or IgA memory B-cells, as categorical variables, with the percentage of responders for serum IgG, IgA and SBA, as well as Student’s t test for the association with mean avidity. All statistical tests were interpreted in a two-tailed fashion using a significance level (α) = 0.05. Data were analyzed using the SPSS version 24 (Armok, N.Y., USA).
Differences between GMTs or GMs at follow up versus pre-vaccination and 3 months post-last injection time points were examined by the Wilcoxon signed rank test for repeated measurements. Correlations between immunological parameters were assessed using Spearman’s rank correlation coefficient. Fisher’s exact test was used to assess unadjusted associations of the frequency of specific-IgG or IgA memory B-cells, as categorical variables, with the percentage of responders for serum IgG, IgA and SBA, as well as Student’s t test for the association with mean avidity. All statistical tests were interpreted in a two-tailed fashion using a significance level (α) = 0.05. Data were analyzed using the SPSS version 24 (Armok, N.Y., USA).
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