In response to the changing viewpoint about the need for annual booster vaccinations, veterinary vaccinologists have recommended new protocols for dogs and cats. These include:

1. giving the puppy or kitten vaccine series followed by a booster at one year of age;
2. administering further boosters in a combination vaccine every three years or as split components alternating every other year until;
3. the pet reaches geriatric age, at which time booster vaccination is likely to be unnecessary and may be inadvisable for those with aging or immunologic disorders.

In the intervening years between booster vaccinations, and in the case of geriatric pets, circulating humoral immunity against the clinically important infectious agents can be evaluated by measuring serum vaccine antibody titers as an indication of the presence of “immune memory.” Titers do not distinguish between immunity generated by vaccination and/or exposure to disease agents, although the magnitude of immunity produced just by vaccination is usually lower.

Except where vaccination is required by law, all animals, but especially those that previously experienced an adverse reaction to vaccination, can have serum antibody titers measured annually instead of revaccination. If adequate titers are found, the animal should not need revaccination until some future date. Rechecking antibody titers can be performed annually thereafter, or can be offered as an alternative to pet owners who prefer not to follow the conventional practice of annual boosters. Reliable serologic vaccine titering is available through Antech at a reasonable cost.

Relatively little has been published about the duration of immunity following vaccination, although new data are beginning to appear for both dogs and cats. The recently published Antech study (JAVMA, October 1, 2000), evaluated 1441 dogs for CPV antibody titer and 1379 dogs for CDV antibody titer. Of these, 95.1% were judged to have adequate CPV titers, and nearly all (97.6%) had adequate CDV titers. Vaccine histories were available for 444 dogs (CPV) and 433 dogs (CDV). Only 43 dogs had been vaccinated within the previous year, with the majority of dogs (268 or 60%) having received a booster vaccination 1-2 years beforehand. On the basis of our data, we concluded that annual revaccination is unnecessary.