Most of my flock has had their Marek's Vaccine. All of the chickens I have gotten were given the vaccine before I got them. And the purebreds that have hatched out were given the vaccine, along with mixed breeds that were sold. But all of these were done by another person, not myself. If I hatched them out, I took them to someone who gave them the vaccines for me. If I bought them, I made sure I ordered them with the vaccine already. There ARE some exceptions, probably including the three chicks I bought last spring from a horrible breeder. And about two months ago, I lost my first chicken - a 7-month old mixed-breed bantam hen - to Marek's. So I've decided to start doing it myself, for ALL of my chicks. After a delayed shipment because of the freezing weather, my 1,000-dose bottle of Marek's Vaccine is due to arrive on Friday. And that's just in time, because I've got one pipped right now. My question is, the "exceptions" - should I go ahead and vaccinate all of my flock that either has not received the vaccine, or that I'm not sure about? I read plenty of things about the problems with vaccinating older chickens. But if you were to "play it safe" would that mean giving them the vaccine.... or not? I know at least one other hen that is about two years old now, and never been vaccinated. She was given to me. And her mixed-breed offspring was the one I lost to Marek's a couple of months ago. So it if were you, and you were getting 1,000 doses of the vaccine (thanks to my diabetic mom who visits the doctor a lot more than most - I have access to that many syringes, too), and you KNEW some of your older chickens probably had not received the vaccine, would you give it to them? Or would you let them go and just hope they were past any possibility of developing the disease's symptoms?