Long-term safety follow up from the third year of the Phase 3 trials and from the third and fourth years of a
Phase 2b long-term follow up study (CYD23/57) conducted in Thailand demonstrated reduction in dengue
hospitalizations among individuals 9-16 years of age for up to two years after completion of the three-dose
vaccine regimen. The pooled relative risk of hospitalization among individuals aged 9 years or older was 0.50,
demonstrating significantly decreased risk in vaccine recipients. However, this risk reduction was not observed
among vaccinated children under 9 years old. The pooled relative risk of dengue hospitalization in this younger
vaccinated group was 1.58 during the third year, suggesting a trend to increased risk. Among the very young
children, this increased risk became more apparent. The relative risk of hospitalization in 2-5 year old
vaccinated children during the third year of CYD14 was 7.45 and in 4-5 year old vaccinated children in the third
year of CYD 23/57 was 2.44