Comparison of anti-RBD IgG for serum optical density values of 272 convalescent COVID-19 patients between wild type, N501Y, and N501Y-E484K-K417N RBD mutant. (a) WT vs N501Y RBD; (b) WT vs N501Y-E484K-K417N RBD. For (a) and (b), Each dot represents the OD value of a single serum, and the line of identity is shown. (c) Box-whisker plot of the OD values, indicating the 5th, 25th, 50th, 75th and 95th percentiles . One-way ANOVA with Tukey's multiple comparisons test was used for statistical analysis. ****, P < 0.0001.