Fig. 4: Relative antibody binding to Omicron or ancestral spike protein in relation to primary virus or vaccine challenge.

A Antibody binding against ancestral Wuhan-Hu-1 or Omicron BA.1 spike in children following three different forms of initial primary antigenic challenge. (i) Initial primary Omicron infection (green; n = 19) and subsequent Omicron reinfection (purple; n = 13) or vaccination (blue; n = 11); (ii) initial primary pre-Omicron infection (yellow; n = 54), followed by secondary Omicron BA.1/2 infection (orange; n = 23); iii) primary vaccination (pink; n = 15) followed by breakthrough Omicron infection (black; n = 6). Inset percentages indicate the geometric mean BA.1 antibody level in respect to the Wuhan-Hu-1-specific antibody level. Data were presented as arbitrary units (AU)/ml. Two-tailed paired Wilcoxon test, bars indicate geometric mean ±95% CI. B Ratio of antibody binding against Omicron or ancestral Wuhan-Hu-1 spike (Omicron/ancestral) in children following initial primary Omicron or pre-Omicron infection, or vaccination as (A). Kruskal–Wallis test with Dunn’s multiple comparisons test, bars indicate median ±95% CI. Source data are provided as a Source Data file.