Fig. 3: Blood IgG antibody profiles around culture-confirmed S. pyogenes events.

a, Individual IgG antibody profiles by age group around microbiologically confirmed S. pyogenes events, where pre-event titers and at least one subsequent titer were measured (n = 163 events). IgG was normalized to pre-event levels. Each dot represents an individual IgG level relative to the baseline titer. Gray lines connect individual participants’ IgG measured before, during and after events. Solid black lines represent the geometric mean log₁₀-transformed IgG level changes across participants, grouped by temporal relationship to the event. Shaded areas around the lines represent 95% CIs. b, Forest plot showing the association between age group and event type with absolute IgG level changes around culture-conformed events (n = 150 events). Points represent estimated group differences, with horizontal bars indicating 95% CIs derived from mixed-effects linear regression models. c, Longitudinal blood IgG profiles in participants (n = 290) without microbiologically confirmed S. pyogenes events during the study period. IgG levels were normalized to individual participants’ baseline titers. Each dot represents an individual antibody titer relative to baseline, and gray lines connect titers measured over time. Dark blue lines represent geometric mean IgG level change from baseline by month, smoothed with the LOESS method. LOESS, locally weighted scatterplot smoothing; ref, reference.