You might also be interested in an important piece of information from the Colorado State University College of Veterinary Medicine Teaching Hospital to consider when deciding on an appropriate vaccination booster protocol for your dogs.
Small Animal Vaccination Protocols The USDA requires challenge data two weeks after last vaccination for licensure for all vaccines (except rabies). The USDA does not require titers or challenge data at one year for any vaccine except for rabies vaccines. Manufacturers yearly vaccine recommendations are arbitrary for all but rabies vaccines.