Fig. 4

Circulating levels of immunoglobulins at 4–8 weeks of infection based on pneumonia development. A The longitudinal cohort study included 252 of these patients who were followed up after 4 to 8 weeks (recovery phase). Blood sampling for ELISA analysis was performed after 4 to 8 weeks (recovery phase). B Circulating levels of IgM, IgA, and IgG at 4–8 weeks of infection in the No Pneumonia (WHO 1; patients without pneumonia) and Pneumonia group (WHO 2–7). Scatter dot plot with mean (wide line). Statistical differences among groups were determined by the nonparametric Mann–Whitney U-test. C Differences in IgM, IgA, and IgG concentrations at 4–8 weeks compared to the acute phase. Statistical differences among time points were determined by the Wilcoxon test. C Heatmap showing the Spearman (ρ) correlation coefficient between serum IgM, IgA and IgG concentrations and age and selected biochemical parameters at recovery phase in pneumonia group (WHO 2–7) based on pneumonia development. D Heatmap showing the point-biserial correlation coefficient (pb) of pairwise comparison analyses between previous comorbidities with levels of the three Igs at 4–8 weeks. Spearman (ρ) matrix and point-biserial (pb) matrix are colour-coded (− 1:1, red: blue through white), and correlations with statistical significance are indicated with an asterisk as *P < 0.05. E Relationship between oxygen requirements and Igs concentrations. Group 0 corresponded to WHO 1 patients without pneumonia, Group 1 corresponded to WHO 2–3 patients with pneumonia but not oxygen requiring and Group 2 corresponded to WHO 4–7 patients with pneumonia and not oxygen requiring. F Heatmap showing the point-biserial correlation coefficient (pb) of pairwise comparison analyses between COVID-19 treatment administrated during acute phase with levels of the three Igs at 4–8 weeks in pneumonia group. Point-biserial (pb) matrix is colour-coded (− 1:1, red: blue through white), and correlations with statistical significance are indicated with an asterisk as *P < 0.05