Fig. 1.

Anti-RBD antibody titres 1.5 and 3 months after the second doses of BNT162b2. A log₁₀ scale was used on the y-axis to minimize data dispersion. In each box-and-whisker plot, the horizontal line represents the median, the top and bottom of the box the interquartile range, and the whiskers the minimum and maximum values. The horizontal line indicates an anti-RBD antibody titre of 4160 AU/mL, which correlates with a 50% inhibitory dilution (ID₅₀) of 1:250 in plaque-reduction neutralization studies. χ² and non-parametric Wilcoxon rank sum tests were used for the following comparisons: (a) anti-RBD antibody titres in blood samples from all study participants (n = 230) measured 1.5 and 3 months after vaccination (p < 0.001); (b) participants with anti-RBD antibody titres that were above 4160 AU/mL 1.5 months after vaccination (n = 199), and 3 months after vaccination (n = 95) (p < 0.001).