FIG 4.

Effect of SARS-CoV-2 variants on anti-spike antibody response to natural infection. Neutralization activities of convalescent-phase serum samples (n = 12, left) and follow-up serum samples (n = 8, right) against wild type, Beta variant, Delta variant, and Omicron variant pseudoviruses. All serum samples were tested with a starting dilution of 1:10 (cutoff, dashed line), and those that failed to neutralize virus at the starting dilution were recorded as half-maximal inhibitory concentration (IC₅₀) titer 5. Each point represents IC₅₀ titer for each sample, and the red line represents mean ± standard error of mean. One-way ANOVA with post hoc Tukey’s test was used to compare the difference among groups. *, P < 0.05; ****, P < 0.0001; ns, not significant.