I have several generations, some of my birds are 10 years old now. My flockmasters are almost all unvaccinated though, as well as the majority of my hens. Only the ones I got from some hatcheries are vaccinated, including the birds that brought it into my flocks. I do not, and will not vaccinate what I or my hens hatch so every bird that is hatched here is unvaccinated.When you said from at least one unvaccinated parent are you still in your second generation? Have you hatched any of your send generation offspring successfully?
I’ve noticed my vaccinated offspring do better than my unvaccinated offspring as I haven’t had any of my unvaccinated offspring make it either.