The Health of a Shelter Dog

Vaccinations and exams don't guaruntee health. The dog could pick up skin infections, parasites, and other problems at the shelter and the symptoms might not appear until you have the dog home.

The dog could also have a genetic health problem thats not looked for during a standard exam. ( hip dysplasia, epilepsy, eye disease)

In addition the stress of being in a shelter, being spayed/neutered while in a stressed state of mind, and being vaccinated on top of all this can be very hard on a dogs immune system and may set the dog up for some illnesses within the months following removal from the shelter.

But you can't guaruntee health on any dog regardless of where it comes from. You can only make sure the dog is healthy on the day you bring it home, and that's the only guaruntee anyone should expect. Just as people can be healthy one minute and sick the next, so can dogs.