After initial vaccines and first year to 14 month booster - I give no vaccines other than state mandated Rabies (and only because I am forced by law!) Lifetime immunity is probably conferred, but studies are ongoing. Just Google canine vaccine guidelines and tons of research from top Vet colleges and researchers comes up. I love my vet for respecting my opinion and "bucking" the tide. When I told him about the research at Cornell Veterinary School, he said "You are preaching to the choir!" He said he has had many a conversation with his colleagues who say that they need the income from annual vaccinations. His answer to them is - that should never override sound medical logic!
LOVE HIM!
Also, FYI -my breeder said no small breed, ie Yorkie should get more than one immunization at a time at a visit, ie Rabies and a combo vac. (one combination vaccine would be ok - just not multiple injections). Can be too much of a stress to the immune system. Oh, and NO LEPTO ever.
This site has a schedule of recommended immunizations and the science explanation behind it:
K9 guidelines