Yes, I am thinking of vaccinating my juveniles. I do have some chicks that I just hatched and more in the incubator, so I will be getting some vaccine just to get it out of the way. My question is, can my juveniles also be vaccinated? I have a pen of juvis ranging from 9 weeks to 16 weeks, can they be vaccinated as well?You probably do want to try to find out what this is, especially if you lose the third bird. There is a vaccine for Mareks. Not everyone's cup of tea but if you know you have a problem, you might want to consider it.