How often should I vaccinate my pets?


Does Rufus need a yearly shot?


With all the conflicting opinions, it’s hard to be sure you are doing the right thing for your animal friend. You may have seen the Market line episode on CBC recently, which among other things featured the topic of annual vaccines for our pets. The episode starred a handsome bulldog that visited 10 different Veterinarians in Ontario and got varying different health recommendations, including differing opinions on the need for annual vaccines. Are yearly vaccines in adult dogs actually necessary?


Research by Ronald Schultz, professor and chair of pathological sciences in the School of Veterinary Medicine, questions whether current vaccination guidelines are causing our pets to be unnecessarily over-vaccinated.


In order to clarify this confusing topic two Associations, the American Veterinary Medical Association (AVMA) and the American Animal Hospital Association (AAHA), compiled a group of experts well versed in how the immune system works. This group is known as the “Canine Vaccination Task Force”. The task force’s main focus was to investigate the necessity of vaccinating our canine companions on a yearly basis. Their findings, known as the “Canine Vaccination guidelines” were published in 2006 and have been updated in 2011.


The task force tested how long a vaccine was protective against disease by “challenging” or exposing adult dogs vaccinated only as puppies to infectious diseases at various intervals through out their life. This length of vaccine protection is called the Duration of Immunity (DOI). Based on these challenge studies, it was discovered that the core vaccines for dogs which protect against the most common and dangerous canine diseases (parvo, distemper and adenovirus) are “expected to induce a sustained protective immune response lasting 5 years” for both parvo and distemper, and “lasting 7 years” for adenovirus. This means that annual vaccinations for parvo, distemper and adeno virus is not necessary in adult dogs that have been previously vaccinated and mounted an adequate immune response. (The exception to this would be dogs that are genetically unable to mount an immune response.) To allow for a window of safety, the AAHA recommends vaccinating adult dogs no more frequently than every 3 years for parvo, distemper and adeno viruses.


What about the non-core vaccines?


Non-core vaccines are made differently and as such they have been found to have a shorter duration of immunity. These include Corona, Canine influenza, Lyme, Leptospirosis, Bordetella. Because of this they may require more frequent vaccination, based on the individual dog. The AAHA recommends these non-core vaccines only for dogs which are exposed to environments containing those specific disease agents and only if appropriate for the individual dog. For example, Corona virus is a disease mainly of puppies and is not needed for adult dogs. Lyme disease, a tick borne disease, has been found in British Columbia although it is present in only certain geographic areas. The exception to this rule is Rabies, which while made in a similar fashion to non-core vaccines, has such as strong immune stimulating effect that the duration of immunity lasts longer than other non-core vaccines. (Vaccination for Rabies is mandated legally differently by each country and state).


For cats a similar studies have been done and the American Association of Feline Practitioners recommends that the core feline vaccines (Panleukopenia, Feline Herpesvirus-1 and Feline Calicivirus) be repeated no more frequently than every 3 years after the first annual vaccination.


Are there side effects to giving vaccines more often than needed?


Yes. Vaccines like all medical procedures do carry the risk of side effects. Vaccines are biologic products and, as such, provoke a series of complex immune reactions that may culminate in rapid-onset side effects lasting from a few hours to a few days. These can vary in intensity from mild to severe allergic or hypersensitivity reactions. Mild reactions such as reduced or loss of appetite (lasting for one or two feedings), pain at the injection site, lethargy (lack of activity), reluctance to walk and/or run, and mild fever are common. More severe reactions while rare, can occur and include: local swelling & pain, ischemic vasculitis, injection site granulomas, local inflammation abscesses, lameness, reactivation of immune-mediated diseases in predisposed dogs, lymphadenomegaly, soreness, abortion, encephalitis, polyneuritis, arthritis, seizures, behavioral changes, hair loss or color change at the injection site and respiratory disease. Other rare reactions include anaphylaxis & death. Immune diseases such as Immune mediated hemolytic anemia in dogs and injection site sarcoma in cats have been linked to vaccination.


Are there risks to not vaccinating at all?

Yes. If not enough animals in a population are vaccinated, then disease can spread like wild fire. A study at the University of Wisconsin-Madison School of Veterinary Medicine in 2008, found that less than 50% of all puppies and kittens are being vaccinated.

"This is an issue, because a population must reach a certain threshold of immunity — called 'herd immunity' — in order to protect the whole group," says Ronald Schultz, a vaccinologist at the School of Veterinary Medicine who has devoted his career to studying the effectiveness of vaccines. "If not enough individuals in a population are protected, disease can always find a new foothold." That fact is especially problematic at no-kill shelters, he says, where bringing in one diseased animal can quickly ignite illness throughout a facility. Dr. Schultz feels that we must make an effort to vaccinate a higher percentage of puppies and kittens and at the same time vaccinate the animal less often. He feels this is the program that will improve “herd immunity” in the safest and most effective way. I agree with this approach. As a Veterinarian I have witnessed unvaccinated puppies die of parvo infection, it is heartbreaking to watch these deaths that could have been prevented by a simple vaccination.

Vaccination is a potent medical procedure that should be undertaken with the same thoughtful consideration as any other medical procedure in veterinary practice. As with most aspects of medical practice, there are benefits and risks to vaccination. Accordingly, vaccination protocols should be individualized to each patient, with consideration given to the medical importance and individual requirements of each patient. I would recommend the basic core vaccines for all young pets, with repetition based on the individual patient’s needs and exposure to disease, in conjunction with the recommendations of the “Vaccine Guidelines for dogs and cats from the World Small Animal Veterinary Association 2010.” Talk to your Veterinarian about a tailored approach to vaccinating your pet.