I have very limited poutry experience. In my brief 2 years of having chickens, the firstyear was the worst. I did not know about vaccinating. I lost about 10% of my flock to something that is inherit on my proerty. And what ever is was, it seemed to be the most harmful to my purebred birds from fancy breeders. One of those fancy big name chickens was a cockerel. And I grew fond of him quickly, then he got sick from this stuff. I wantd to get him inside to take care of him and I did not care that I ws exposing him to everything in my brooder room. The cockerel eventually died in that room. From that experience, I learned that most every chick who I raised up, and survived from that time, who was in the room is immune to this crap. No one has died from it in close to a year, chick or adult. Then a friend told me what I did was what his grandpa did back when he was a boy. This friend is clos to 65 years old. He said back then there was no TSC, no needles, no one vaccinating. And I know I should vaccinate. It is a crap shoot IF I don't. I do not advocate what I do. It is just my experience in chickens. And I like them to be alive till I want them dead.