The possibility of contracting this disease in my flock from a new bird terrifies me. I hatch other people's eggs with my own and keep them quarantined for six weeks. I quarantine any new birds buildings away from my birds with bleached quarantine shoes to change into at the entrance..I put young cockerels in with new quarantined birds to see if they catch a carried disease for four weeks before integrating with my flock. I have never had any type of disease in my flock. I vaccinate against mareks, and fowl pox. Here is my question: Since my flock is totally disease free, could I vaccinate all of them against MG...chicks to adults? My goal is to keep a new carrier bird from slipping by all my safety precautions. The vaccine is over $100, but I don't know if it's reasonable to vaccinate birds that have already been put outside. I don't care about the cost...I just don't want to have to start over if there is an outbreak because I sell and trade birds and hatching eggs. Is the vaccine effective in older, healthy birds?