All you can do with a pet with a "history" is be extra nice to them to try to make it up . . .
We haven't had him fully vetted. My horse vet looked him over briefly soon after Homer showed up here. We wormed him because I could see tapeworm segments coming out of him, but we haven't had him in for shots yet. I don't panic about shots in older dogs as much as we would a puppy. We don't have any rabies or distemper around here to speak of, and if he hadn't already had shots in his life he wouldn't have made it to 3 months old without Parvovirus vaccine. Adult dogs don't get it.
Our vet budget needed a break after the winter teeth and sheath appointment for the horses. We'll take him in when Gidget is due for shots this spring.