Pooled rates of efficacy for symptomatic dengue during the first 25 months were 60.3 % ( 95 % CI , 55.7 to 64.5 ) for all participants , 65.6 % ( 95 % CI , 60.7 to 69.9 ) for those 9 years of age or older , and 44.6 % ( 95 % CI , 31.6 to 55.0 ) for those younger than 9 years of age .