Response

In reviewing the letter from the ACVM Committee, we appreciate their comments and their general support of the AAHA Canine Vaccine Guidelines. Three ACVM Diplomates participated in the AAHA Task Force, and their contributions were invaluable.

We note that the ACVM review committee supports the concept of individualized vaccine recommendations based on risk and exposure factors, as well as the opinion of the veterinarian charged with making a recommendation to the pet owner. The committee also supports the classification of various antigens into 1) core or recommended, 2) non-core or optional, and 3) not generally recommended. These classifications should be interpreted and applied to each animal based on risk of exposure and probable benefit of vaccination for the animal.

We are not in disagreement regarding the administration of products designed to protect against diseases with limited or regional distribution. Leptospirosis and Borrellia burgdorferii may well warrant vaccination, but only with consideration of the likelihood of exposure, the benefit to the patient, and with involvement of an informed client. Some diseases may be of regional significance, and in those cases vaccines should be given. In other words, the optional vaccines may, in a given situation (with the understanding of the owner and at the discretion of the clinician), become core vaccines in that practice. The point is that no vaccine other than those deemed as core vaccines should be given as a matter of routine.

The ACVM Committee also endorses the fact that adverse events must be monitored and reported appropriately to the manufacturers or directly to the USDA Center for Veterinary Biologics. Only with improved documentation and reporting can the true safety and efficacy of vaccines be determined in large populations.

The ACVM’s areas of disagreement center on the terms “sterile immunity” and “duration of immunity,” and the paucity of published supportive documentation already acknowledged by the Task Force. The guidelines state clearly that the recommendations are based on a combination of expert opinion and clinical experience. The guidelines were not published as a scientific study but as a report from an assembled task force. The guidelines were produced not as a definitive study, but as a tool to assist veterinarians in making decisions for their patients.

As stated by the AVCM Committee, the outbreak in Finland was attributed to a decrease in the vaccinated population, as well as a failure in efficacy of a widely used vaccine. In other words, the outbreak occurred because not enough dogs had been initially protected, and many vaccinates received a less than effective vaccine. Such widespread failures could be avoided if manufacturers were required to test individual lots of vaccines once licensed.

The report from Japan involved a group of puppies that had been vaccinated one or more times. There is no assurance that repeated vaccination produces immunity in all patients, and some animals respond poorly, if at all. There is little, if any, evidence that street viruses and vaccine viruses present significantly different antigenic patterns. It would seem likely that if this were the case, vaccine breaks would be much more common.

Since the release of the AAHA Vaccine Guidelines, at least one study was published that supported the likelihood of protective immunity persisting 3 years after vaccination. Additionally, as of this time, one major manufacturer has released a product tested and licensed for revaccination of adult dogs that provided protective immunity for 3 years.

Notwithstanding references to far greater duration of immunity, the AAHA guidelines stipulate that triennial revaccination of adult dogs is probably protective. We note that the ACVM committee points out that the 1-year and the 3-year vaccination intervals are not based on controlled, peer-reviewed studies and that increasing vaccination intervals from 1 year to 3 years is a reasonable recommendation. The recommendation of the Task Force is that more dogs be vaccinated, but revaccination should be done less frequently.

The recommendations of the AAHA Canine Vaccine Guidelines Task Force are essentially that the profession should vaccinate as many animals as possible against appropriate agents, but no more frequently than indicated. At the discretion of the veterinarian, we encourage the revaccination of adult animals on a triennial basis. The guidelines stress vigilance and reporting of adverse events, including failure to protect. The guidelines also stress the individualization of vaccination recommendations and the involvement of an informed client in developing patient-specific recommendations.

We again thank the ACVM for their recognition of our efforts, for the participation of their members, and for their general support of the guidelines as published.