Hi Everyone, Sorry if this has been discussed before and I missed the thread: I just ordered 27 day-old chicks that will arrive on April 20. They will be vaccinated against Marek's. But as I looked through the records of last year's order of 16 girls (that my beloved husband placed), I noticed that these birds are not vaccinated against the disease (). Thankfully, they are now over 9 months old and healthy. Should I be concerned about having a vaccinated and non-vaccinated birds on the farm? Is it possible (and effective) to vaccinate the older birds as well? I've tried to find information on the Internet, but it's contradictory and confusing. Thanks!