i think this question has come up before, but not sure there was any consensus. But i just read on another thread someone commenting that if you bring vaccinated birds into your flock they shed cells from those vaccinations or a long time and will infect your existing birds with that disease. Here is why i'm asking. i have several different pens, mainly bantams. Then i have one lonely four-year-old easter egger, Penny, that has lost her friends and needs a buddy. i am so leery of bringing in any new chickens, after having a bad experience last year, so basically have a closed flock. But this one chicken needs a friend. i have not vaccinated for anything except fowl pox. Have never had Marek's on the property. Last year, though, when i had some chickens necropsied for other things, several showed latent Marek's. When i spoke to the State Vet, he said that Marek's is so common that most all birds have been exposed at some point. These latent Marek's chickens were in the same pen as Penny, so i suspect she has been exposed to Marek's but has resistance to it (?). So, talked to someone yesterday about adopting a pullet from him. He said his birds have been vaccinated for Marek's. Will bringing this bird into a pen with Penny put her at risk? And then will it put my other pens at risk if i traipse droppings or feathers on my shoes? Thanks for any insight anyone might offer.