Reseach is showing that a dog regularly boostered with the DLLPwhatever and Rabies every three years, has a lifelong immunity and that over vaccination contributes to an aging dog's deterioration of the immune system. You know and I know that I am going to have to give the Rabies to satisfy the state, but I can stop the others.
Lepto may be what you're thinking of with the squirrels. After much internal debate, I do vaccinate my dogs for that because our walking area includes woods shared with bear, coyotes, etc and a lake area shared with the squirrels and bears. Standing water after a rain can become contaminated.
I killed a wonderful dog with over vaccination. I will never do it a second time.