types (replacement disease) were unlikely to be
substantial this early in the PCV program.16
The difference in rates and the associated
95% confidence intervals were used to assess the
significance of the observed changes in invasive
pneumococcal disease. The chi-square test was
used to evaluate differences in proportions. Two-
sided P values of less than 0.05 were considered
to indicate statistical significance. Stata software,
version 12 (StataCorp), was used for analysis