In the CYD14 trial, prespecified age-specific
analyses showed a clear trend toward a higher
relative risk for hospitalization for virologically
confirmed dengue among younger children, although
the number of cases was low; the relative
risks were 7.45 among children between the ages
of 2 and 5 years, 0.63 among those between the
ages of 6 and 11 years, and 0.25 among those
between the ages of 12 and 14 years (Table 1). The
prespecified age-specific analyses in the CYD23/57
trial showed a relative risk of 2.44 (95% CI, 0.27 to
115.34) among participants who were 4 or 5 years
of age during year 3 (Table 1). In year 4 of the
CYD23/57 trial, the relative risk among children
who were 4 or 5 years of age was 0.81, but the
upper boundary of the 95% confidence interval
remained more than 1 (95% CI, 0.16 to 5.24).
Further analyses in the CYD15 trial, in which
participants between the ages of 9 and 16 years
were enrolled, showed no trend according to age
group among those who were between the ages
of 9 and 11 years and those who were between
the ages of 12 and 16 years.
In year 3, the relative risks among participants
younger than 9 years of age were similar
in the CYD14 and CYD23/57 trials, with a pooled
estimated relative risk of 1.58 (95% CI, 0.83 to
3.02), which suggests an overall trend to increased
risk in the vaccine group, although the
lower boundary of the 95% confidence interval
was less than 1 (Table 1). The relative risk