I have a flock of mixed ages ranging from 1 week old to 6 years old. I'll be getting a few vaccinated birds, however, I have never vaccinated my flock. I realize that the vaccine won't make the new birds carriers, but it will hide whether or not they actually have the disease. As far as I know, I have never lost a bird to Marek's disease. Other members on this site have told me that my flock is most likely resistant because nearly all chickens are exposed at some point in their lives. I'd like to vaccinate my flock (better to be safe than sorry), but first I want to make sure there aren't any risks to the vaccine. I can vaccinate my entire flock no matter what the age, correct? If so, should I give them all the same dose of 0.2 ml? They will not develop symptoms of Marek's disease from the vaccine, correct? I plan to share the vaccine with a neighbor and she raises both chickens and turkeys, is it safe for her to vaccinate her flock? even if it's the turkey strain of Marek's in the vaccine? I received my starter flock when they were already 1 year old and I don't know whether or not they have already been vaccinated. In case they have, would it hurt to vaccinate a second time?