SARS-CoV-2 neutralization assays were performed by using pseudoviruses expressing the spike protein of WA1/2020 or the Omicron subvariants in 293-ACE2-TMPRSS2 cells. SARS-CoV-2 neutralization titers were determined in each of the prepandemic 2019-IVIG (n = 20), 2020-IVIG (n = 8), 2020 convalescent plasma (2020-CP; n = 7), 2022 convalescent plasma (2022-CP; n = 8), post-infection hyperimmunoglobulin IVIG (pi-hCoV-2IG; n = 17), 2023-IVIG (n = 9), 2024-IVIG (n = 5), and post-vaccination hyperimmunoglobulin IVIG (Vx-hCoV-2IG; n = 1) preparations. The assay was performed in duplicate to determine the 50% neutralization titer (PsVNA50). The heights of the bars and the numbers over the bars indicate the geometric mean titers, and the whiskers indicate 95% confidence intervals. The horizontal dashed line indicates the limit of detection for the neutralization assay (PsVNA50 of 20). Differences between SARS-CoV-2 strains were analyzed by ordinary 1-way ANOVA with Tukey’s pairwise multiple-comparison test in GraphPad Prism version 9.3.1 and the P values are shown.