Hello, I have had to deal with Marek's for 2 years now since I brought home a batch of hens from an auction; WHICH I WILL NEVER DO AGAIN!!! (as per my own diagnosis with the like symptoms posted on this site regarding Marek's.) Okay, from this point oN... my next batch of peeps will be innoculated for this devasting disease. I DO have several adult birds and a roo that have not fallen prey to this disease, so here is my Question....Can I innoculate the adult birds that I have, and if not, why....