Figure 2.

Products were analyzed by expiration year, for IgG binding activities against (A) recombinant SARS-CoV-2 RBD, (B) spike, and (C) NP using ELISA. Data points represent area under the ELISA curve, separated by product expiration year. These was a significant increase in AUC in Ig products with expiration dates of 2023 compared with prepandemic products. The increasing trend in AUC continued across all 3 protein assays for expiration years 2023 and 2024. Error bars indicate mean and SD. Exp., Expiration. ∗P < .05; †P <.01; ‡P < .001; §P < .0001. A 1-way analysis of variance with Kruskal-Wallis test was performed for statistical analysis