As early as 1997 a limit in the frequency and amount of vaccines given was noted in the veterinary community:
FIRST INTERNATIONAL VETERINARY VACCINES AND DIAGNOSTICS CONFERENCE, Madison, WI, July, 1997 http://www.thepetcenter.com/exa/vac.html
*Avoid vaccinations before six weeks of age. Give two to four doses of vaccine spaced three to four weeks apart.
*Give annual booster vaccine at one year of age. Thereafter give boosters every three years, unless required more often by law.
*Vaccinate puppies and kittens against the clinically important infectious agents such as distemper virus, parvovirus, panleukopenia and rabies.
*Monitor serum antibody levels annually between boosters. ( This means that your dog or cat should have a blood test done to measure the level of “immune memory” to a disease.)
*Geriatric animals generally do not need booster vaccinations. Monitor serum antibody titers instead.