Fig. 2: Lower magnitude but long-lasting maintenance of children’s convalescent IgG.

Children samples in red (PRNT50 n = 58 Spike (S) n = 111 OC43 S/ Nucleocapsid (N)/ ORF8 (n = 82), S2 (n = 81) and adults in black (PRNT50 n = 40, Spike n = 82, OC43 S/S2/N/ORF8 n = 80), neutralising antibody titres (A), IgG responses (B–F) at convalescent timepoints (from day 15 post symptom onset or hospital admission). Dotted lines represent a responder cut off based on the mean+2 SD response of 48 pre-pandemic controls, and % donors with responses above the cut off shown in grey boxes below. Individual data points are shown, with lines and error bars showing mean and standard deviations. Lower bars are not shown if at 0 or below. Differences between groups were assessed using a two-sided Mann-Whitney test with exact p values up to 4 significant figures shown. Antibody levels directed against SARS-CoV-2 S up to 180 days post symptom onset or hospital admission (G) or against SARS-CoV-2 N up to 138 days (H). For S-IgG,122 samples from 85 adults are depicted in black and 231 samples from 137 children are shown in red (G) while, for N-IgG, points represent 113 samples from 84 adults in black and 158 samples from 106 children in red (H). Ratio between IgG and IgM in infected children, adults, uninfected children and uninfected adults against S, N, ORF8 and OC43 S (I–L) with dotted likes at 1 for equal ratio. Differences between groups assessed with two-sided Kruskal-Wallis test with Dunn’s multiple comparisons correction and exact p values up to 4 significant figures shown. M Longitudinal plot of IgG-to-IgM ratios targeting S tracked until day 104. Data include 103 samples from 77 adults and 55 samples from 42 children. (N) Longitudinal plot of IgG-to-IgM ratios targeting nucleocapsid up to day 138. Points represent n = 104 samples from 79 adults in grey and n = 74 samples from 52 children in red. G, H, M, N Fitted values are derived from GAMM accounting for participants’ ID as a random effect and, as a fixed effect, age group, symptoms and sex (G), age group and symptoms (M) or only age group (H, N). 95% confidence intervals are depicted by the shaded areas. The p-value corresponds to the significance of age group as a parametric coefficient in the model and the average decrease of response in children compared to adults is indicated. Source data are provided as a Source Data file.