I have not vaccinated for about 5 years now. All the vaccinated adult hens are either old biddies or active breeders. A good portion of the younger ones now have ameraucana blood in their background as well which seems to help as ameraucana aren't easily susceptible to Mareks and silkies are very susceptible.
I fully understand wanting to get them vaccinated. It's not cost efficient for me to vaccinate at the moment because it's $60 shipping and $30 each vaccine. If I was hatching a lot it would be doable.