I have about 6 ~ 20+ week old chickens from TSC, 14 ~ 16+ week old chickens I hatched myself and 25 ~ 6 day old chicks from MPC. None are vaccinated as I know of. Not sure of the 6 TSC chickens. I have the Marek's vaccine in the refrigerator ready for administration. So, do I vaccinate the older birds and the younger or do I not do anything. I'm at a loss. Does it do any good for older birds? If I vaccinate the young ones will it put the old ones at risk? What do I do and where is the information on vaccinating older birds? TIA