The studied enrolled 3174 healthy children between the age of 12 and <36 months whose parent or legal guardian gave written consent over 5 Table 2 , the efficacy of the vaccine against culture-confirmed illness was estimated to be 74.3% (95% CI 64.1-81.8) overall and the point estimates of efficacy against H1, H3 and B influenza infection were 82.3, 88.8, and 50, respectively.