Hello, everybody I know that if I going to vaccinate against Mereck disease I have to do it 24 hour after the hatching. But what happens if I vaccinate my adults chickens? they develop the disease ore is not benefits on doing it becose they don't develop inmunity against the mereck virus as adult and if that is the case, why is like that? any imput will be appreciated, I will love to hear yours experiences about this matters.