Fig. 2

Dynamic profiles of the antibody levels during a 2-year follow-up period in 350 children immunized with the vaccine. Blood samples from 350 participants, who provide a full series of blood samples within the 2-year follow-up period, were collected to evaluate the production of anti-EV71 neutralizing antibodies. These children were 6–11 months old (a) (48 individuals in the vaccine group and 50 in the placebo group), 12–23 months old (b) (50 individuals in the vaccine group and 63 in the placebo group), 24–35 months old (c) (43 individuals in the vaccine group and 52 in the placebo group), and 36–71 months old (d) (20 individuals in the vaccine group and 24 in the placebo group). The geometric mean titres are shown above the bar. The bar indicates the 95 % confidence interval