This figure shows that the mean number of hospitalisations per year in the pre-vaccine period was more than double than for the post-vaccine period for all age groups in children aged under 5 years. The most dramatic decreases were for children aged 6-11 months, 12-23 months and 24-35 months. For children aged 12 to 23 months, average hospitalisations decreased from 26.7 to 5.2 per year.