Extended Data Fig. 1: Blood IgG antibody profiles around culture-confirmed S. pyogenes events.

a) Blood IgG antibody levels around microbiologically confirmed events. IgG levels from paired samples before and after a microbiologically confirmed event in the SpyCATS study (n = 150) were measured. IgG levels were compared using a paired Wilcoxon signed-rank test. Median IgG level is represented by centre line. P-values were adjusted for multiple testing using the false discovery rate (FDR) correction. b) Absolute Blood IgG increases around culture confirmed events by event type. P values are derived from Kruskall-Wallis tests to compare absolute IgG increases between multiple event types. No significant differences between groups were observed. Box plots show medians, IQR, 1.5×IQR whiskers and outliers. c) Individual IgG antibody profiles by age group around microbiologically confirmed S. pyogenes events, where pre-event IgG levels and at least one subsequent IgG level were measured (n = 163 events). IgG was normalized to pre-event levels. Each dot represents an individual IgG level relative to the baseline level. Grey lines connect individual participants’ IgG measured before, during and after events. Solid black lines represent the mean log₁₀ transformed IgG level changes across participants, grouped by temporal relationship to the event. Shaded areas around the lines represent 95% confidence intervals calculated using the mean and standard error of the log-transformed IgG levels. d) Association between baseline (pre-event) IgG level and absolute increase in IgG level between pre and post event (n = 150 events). Pearson’s correlation coefficient (r) was calculated for each antige, using a two-sided test without correction for multiple comparisons.