Immunoglobulin G (IgG) dynamics in the first week after vaccination by presence or absence of post-vaccination fever. The red and blue lines show the IgG concentration means predicted by the mixed-effects model in the febrile and nonfebrile groups, respectively. The area of each color indicates the 95% confidence interval (CI) of the regression curve. Day 0 is a negative value owing to the effect of the modeling prediction.