Yes I agree with you, I already mentioned that I am not expert in this field but I heard that the vaccines are good for chicks when they are grown up in the cages and some sort of bounded areas, these vaccines are not necessary for those chicks which are grown up in natural environment. So if you have provided the natural environment for your chickens than you have to feed them naturally and no need of any chemicals to inject in the bodies of your chickens.
Sorry for inconvenience as my comments was not up to your understanding Sir.