Pseudovirus neutralization test results. (A-C) NT50 by sex (A) and age (B,C) after 1 month or 12 months. (D–F) Neutralization analysis of convalescent serum against the WT (D), Delta (E), and Omicron (F) pseudoviruses at 1 month and 12 months after recovery. The neutralization activity of serum from 64 patients who had recovered from COVID-19 was tested. Data represent the ED50 of three independent experiments. (G, H) Convalescent serum neutralization sensitivity against Delta and Omicron at 1 month (G) and 12 months (H) after recovery. The neutralization ED50 and ratio compared to the origin strain WT is indicated. Data represent the ED50 of six independent experiments. (I-K) Correlation between live virus-neutralizing antibody titers and pseudovirus-neutralizing antibody titers of WT, Delta and Omicron strains. Statistics were calculated using Kruskal–Wallis test with Dunn's multiple-testing correction (A-C, G-H), Mann–Whitney U test (D–F). Correlations were assessed by two-sided Spearman rank correlation tests (B-C,I-K).