Many pets may be getting vaccinated too often and unnecessarily, with potentially grave ramifications. Despite international advice and updated professional guidelines from the Australian Veterinary Association (AVA) introduced in 2009, many adult cats and dogs still receive injections annually, instead of the now recommended cycle of every three years.

Some non-core vaccines, such as the kennel cough vaccine, still need to be done annually, but researchers now believe there are good reasons why core vaccines should be triennial.

The risks in over-vaccination

Routine annual revaccination of adult animals became the accepted norm from the 1950s through to the 1990s, when US vets noticed an alarming increase in the number of tumours occurring in cats. These "new" tumours were located in parts of the body where the vaccine was typically injected – for example, between the shoulder blades. An association between injection of adjuvanted vaccines against both the leukaemia virus and rabies and the development of injection-site sarcomas (malignant tumours) in cats was soon confirmed.

By 1997, experts began to question whether adult cats and dogs were being over-vaccinated. Several American veterinary schools switched to a triennial schedule of booster vaccinations against core viruses. Massey University in New Zealand followed suit three years later.

In 2007, the World Small Animal Veterinary Association (WSAVA) began advising vets to continue vaccinating pets with core vaccines, but to reduce their frequency to minimise the potential for adverse reactions.

In Australia, the AVA issued a revised policy in June 2009 stating that in most cases core vaccines need not be administered any more frequently than triennially, or even less so under certain circumstances, such as if your pet is kept inside and less likely to come into contact with these viruses.

WSAVA released revised guidelines in 2010 stating that "core vaccines should not be given any more frequently than every three years after the 12-month booster injection following the puppy/kitten series, because the duration of immunity (DOI) is many years and may be up to the lifetime of the pet".

Why are vets not on board?

It's been several years since the AVA recommend triennial vaccinations, but many vets continue to recommend annual vaccinations and pet owners are simply not being told about the new guidelines.

There are a couple of obstacles in the way of ensuring all Australian vets operate by the new guidelines.

  • Vaccine labelling – the Australian regulator, the Australian Pesticides and Veterinary Medicines Authority, can't change vaccine labels to the new three-year recommendation without data being provided by the manufacturer to prove a longer duration of immunity (DOI). Manufacturers are only required to provide a minimum DOI. There is more on this issue below.
  • Self-regulation – the veterinary profession is self-regulated, and vets are not required to join the Australian Veterinary Association (AVA) or follow its guidelines.

There is also data to suggest some vets may be reluctant to make the change as it would impact their income. A vet industry survey in 2005 found "89% of veterinarians indicated that dog and cat vaccinations were the number one contributor to practice turnover, and 91% of vets felt that a change from annual vaccination would have an adverse effect on their practice turnover".

Labels as a sticking point

In 2010, Dr Richard Squires, an associate professor and Head of Veterinary Clinical Sciences at James Cook University, told CHOICE that vets may be reluctant to switch to triennial vaccinations because they're closely following the manufacturer's recommendations on the label. "To use vaccines in an off-label manner may lay the vet open to serious legal consequences if a vaccine used off-label failed to protect an animal."

But vets aren't obliged to follow recommendations on vaccine labels – state and territory legislation allows vets to use vaccines at whatever interval they determine is best, provided they obtain informed consent from the pet owner. In addition, the APVMA told CHOICE that most core vaccines have now changed their "annual revaccination required" to "This product has been assessed as providing at least 12 months protection", or something similar. The new wording gives vets even greater latitude to determine longer re-vaccination intervals.

Guidelines for vaccinating your dog or cat

Maternal antibodies in a kitten or puppy are soon lost after birth. WSAVA recommends puppies and kittens are first vaccinated at 8–9 weeks of age, followed by a second vaccination 3-4 weeks later and a third given between 14 and 16 weeks, followed by a booster at one year.

WSAVA says 98% of core vaccinations given between 14 and 16 weeks will actually provide immunity for many years, and probably even for the life of the animal. So if the dog is already immune to the three core diseases, re-vaccinating will not provide any extra immunity.

After one year of age

  • Bring your pet to the vet every year for an annual health check. Discuss with your vet the most suitable vaccination regime for your pet.
  • If you're concerned that your pet may be vaccinated unnecessarily, ask to have antibody titre testing done. This will tell you if your pet is already immune. It can be done for all the core viruses for dogs and cats so ask your vet if they offer it.
  • To reduce the risk of tumours, feline adjuvanted vaccines should not be injected into your cat's back.
  • Don't be shy to ask questions, and get a second opinion if in doubt.
  • Report any unsatisfactory experiences to your state's veterinary practitioners' board.
  • If your pet has a negative reaction to any vaccination, such as a loss of appetite or a swollen face, contact your vet immediately and report the case to the APVMA on 1800 700 583.

Which vaccines and how often?

Core vaccines

Core vaccines are those that should be administered to every puppy or kitten, and should be used in adult animals in a manner that maintains robust protection for life. International and AVA guidelines recommend these core vaccines be administered triennially.

The core vaccines protect against:

  • Dogs – canine distemper virus, canine adenovirus (which causes infectious hepatitis), canine parvovirus
  • Cats – feline parvovirus (also known as feline enteritis and feline panleucopaenia), feline calicivirus, feline herpesvirus.

Non-core vaccines

Non-core vaccines are those that don't need to be administered to every animal. This could be because the disease(s) they protect against are relatively mild, the animal has little chance of exposure to the disease, the vaccine causes adverse effects, making the risk-benefit ratio unattractive, or there is insufficient scientific information to allow an informed decision about the need, efficacy and/or safety of the vaccine. Speak with your vet to find out if these are required. If non-core vaccines are required, they may need to be administered annually.

Non-core vaccines protect against:

  • Dogs – canine parainfluenza virus, Bordetella bronchiseptica, Leptospira interrogans
  • Cats – feline leukaemia virus, Chlamydophila psittaci, feline immunodeficiency virus

Common "combined" vaccines for dogs

  • C3 (core): Parvovirus, distemper and infectious hepatitis
  • C4: C3 + parainfluenza virus
  • C5: C4 + Bordetella bronchiseptica

Common "combined" vaccines for cats

  • F3 (core): Feline parvovirus and the two viruses that cause feline respiratory disease (feline calicivirus and feline herpesvirus)
  • F4: F3 + leukaemia virus
  • F5: F4 + immunodeficiency virus