Unless you are a big producer of hens, it's hard to vaccinate them as most vials are for 1000 doses.
They would have had to have been done at intervals when they were chicks and growers for most vaccines.
Vaccines exist to stop big losses in commercial farms - but - generally speaking hobby breeders don't vaccinate and you shouldn't encounter any serious diseases outside of the commercial environment.
Yes,that's something I forgot to mention Snifter - free range chooks develop natural immunity with age over the generations so if you keep them healthy and immune system well 'fed' they shouldn't normally go ill.