I am fully aware of that, however factors like whether you show and whether the home has had others chickens plays a role as well. Again, there is no 100% guarantee, even vaxed birds have had it, this is a choice that each has to make for themselves.
I can only share what i did and my circumstances by no means am i advocating a certain way of going, now that all out of the way lol.. I chose not too. My 4 little balls of fluff are they only chickens on the farm, they are not shown, nor do i show birds period. My flock is closed. I did a...