Health education about HFMD and
herpangina, given in early May, had
reached 82% of parents of casechildren
and 91% of control-children
(OR: 0.45). The median age of both
case-children and control-children
was 3 years, but there was a statistically
significant difference in the age
distribution (P .05; Kruskal-Wallis
test). We did a stratified analysis of
the data in Table 2 with additional
stratification by age group (6 months
to 1 year, 2–3 years, and 4 – 6 years),
which showed only minor differences
in the ORs and no changes in statistical
significance of individual exposures
(in addition to observing no heterogeneity
of the OR among the age
strata).