Figure 1. IgG and IgA antibody responses to SARS-CoV-2 invaccinated 2-year convalescents.
A, Schematic overview of workflow to detect the immune memory in vaccinated 2-year convalescents and healthy controls with vaccination. A total of 112 individuals were recruited for the analysis in Macheng and Beijing, and they were classified by whether they had prior exposure to SARS-CoV-2 and vaccination. 23 of 51 COVID-19 convalescents were enrolled in the follow-up study at 6 months, 1 year, and 2 years after symptoms onset.
B-I, IgG and IgA antibody levels were measured by MCLIA and ELISA in healthy individuals after being vaccinated (HC-Vac, green, n=35) or unvaccinated (HC-Unvac, blue, n=26), and in COVID-19 convalescents following at 6 months (6m, orange, n=23), 1 year (1Y, green, n=23) and 2 years with vaccination (2Y-Vac, red, n=51). B-C, Anti-SARS-CoV-2 IgG antibody titers determined by ELISA (B) or MCLIA (C). D-E, The longitudinally dynamic changes of IgG levels in convalescents at 6 months, 1 year, and 2 years in the same individuals after symptoms onset, using ELISA (D, n=23) or MCLIA (E, n=18). F-G, Correlation of IgG titers and different disease severity in 51 vaccinated 2-year convalescents (2Y-Vac), including Asym-Mild (Asymptomatic and Mild, red, n=25) and Mod-Sev (Moderate and Severe, dark green, n=26). H-I, IgA antibody levels measured by MCLIA were shown in HC-Vac and 2Y-Vac groups (H, HC-Vac: n=35; 2Y-Vac: n=51). The dynamic changes of IgA antibody responses during the 2-year follow-up (I, n=18). The dotted lines reflect the cut-off values for positive antibody titers. Significant differences in antibody titers were tested using a Mann-Whitney U-test (B-C, F-H). A Wilcoxon matched-pairs signed rank test was used to compare IgG antibody titers at three time points (D-E, I). * p < 0.05, ** p < 0.01, *** p < 0.001.