Two questions- efficacy and 2 doses

[Anonymous]

Does anyone know the efficacy after two doses (or even one) for kids?
Meaning- what is the chance you are covered from the flu?

Secondly, if this is made "just like the regular flu shot" but a different strain, why do kids need two doses? (aside from kids getting a shot for the very first time) In other words, kids who have gotten the flu shot every year, why 2 of this one?