Well the title mostly says it all. I've started a few threads already about the same topic, but I still haven't found the answer I've been looking for. Maybe I'm missing something here? I don't know. Anyway, I ordered 10 baby chicks about two months ago from mypetchicken and I had them vaccinated for mareks and two more just a month ago from a local feed store that aren't vaccinated. The two baby chickens aren't as big as I want them to be yet to let them out with the older chickens but once they are..they'll be out with the rest now back to the question haha is it safe to be mixing chickens that have and have not been vaccinated? Sorry for the post.