Pooled relative risks of hospitalization for dengue were 0.84 ( 95 % confidence interval [ CI ] , 0.56 to 1.24 ) among all participants , 1.58 ( 95 % CI , 0.83 to 3.02 ) among those under the age of 9 years , and 0.50 ( 95 % CI , 0.29 to 0.86 ) among those 9 years of age or older .