Vaccinations and Titre Testing For Cats

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  • What is a titre test?

    A titre (pronounced tighter) test is a measurement of how much antibodies a cat has against certain pathogens (disease-causing organisms). Antibodies are Y shaped proteins produced by B cells in response of an antigen (a toxin, foreign substance or pathogen which induces an immune response in the body, especially the production of antibodies). They bind to the pathogen to stop it from replicating, and also tag pathogens so that other blood cells know to destroy them.

    When a cat is vaccinated, it receives a weakened or killed version of the pathogen which stimulates the immune system to produce antibodies. These remain in the body long after the pathogen has been eliminated and the titre test measures levels of antibodies. However, over time, antibody levels can drop, which is why re-vaccination is necessary to ensure the cat continues to be protected against specific organisms.

    All kittens should receive a series of two or three CORE vaccines at 6-8, 10-12 and 14-16 weeks and previous guidelines stated an annual booster was necessary 12 months after the 16-week vaccination.

    Core (F3) vaccination:

    Core vaccines consist of three pathogens that affect cats globally and every cat should receive the core vaccine.

    Non-core vaccinations:

    Non-core vaccines are for at-risk cats due to location, lifestyle and council or government regulations (outside cats or cats in endemic areas)

    • Rabies – In many parts of the world this vaccine is compulsory for all pets.
    • Feline immunodeficiency virus (FIV)
    • Feline leukemia virus (FeLV)
    • Chlamydia
    • Bordetella
    • Feline infectious peritonitis (FIP)

    Guidelines have changed in recent years to every two/three years for low-risk (indoor only) cats. However, despite the Australian Veterinary Association (AVA), the World Small Animal Veterinary Association and the American Association of Feline Practitioners (AAFP) stating their stance or guidelines, many veterinarians still recommend annual vaccinations which are confusing to pet owners who want to do the best for their cat.


    Cats that have responded to vaccination with MLV core vaccines maintain a solid immunity (immunological memory) against FPV for many years in the absence of any repeat vaccination. Immunity against FCV and FHV-1 is only partial (Scott and Geissinger 1999, Jas et al. 2015). The VGG recommendation for adult ‘low-risk’ cats is for revaccination with MLV core vaccines at intervals of 3 years or longer.

    Note: The recommendation above states MLV (modified live vaccine), most core vaccines in Australia are killed; however, the third quote below relates to killed vaccines and the guidelines are the same.


    The AVA supports administration of core vaccines to all companion animals to protect them against severe, life-threatening diseases that have a global distribution. Vaccines with extended duration of immunity (e.g. triennial) may be used for core vaccination in adult cats and dogs where risk of disease does not necessitate more frequent revaccination; however, local animal and environmental factors, including but not limited to increased risk of infection (e.g. increased incidence in the population, upcoming boarding) and acknowledged lack of sterile immunity with some core vaccines (e.g. feline herpesvirus 1 and feline calicivirus) may dictate a more traditional annual core vaccination schedule in some situations.


    A single dose is given one year following the last dose of the initial series, then no more frequently than every three years.

    The three quotes above are just a few lines taken from an entire guideline, paper; there is no one size fits all when it comes to vaccinating cats. Each veterinarian must assess the cat’s individual risk.

    Just to confuse things, some veterinarians state that while immunity from panleukopenia may last longer than three years, that is not the case for feline herpesvirus or calicivirus (my own veterinarian included). However, one paper states that while protection against panleukopenia lasts longer than that of feline herpesvirus or calicivirus, during trials, test cats remained seropositive against FHV and calicivirus for 3-4 years after vaccination. The killed (inactivated) vaccine was used in this case.

    Control cats remained free of antibodies against FPV, FHV, and FCV and did not have infection before viral challenge. Vaccinated cats had high FPV titers throughout the study and solid protection against virulent FPV 7.5 years after vaccination. Vaccinated cats were seropositive against FHV and FCV for 3 to 4 years after vaccination, with gradually declining titers. Vaccinated cats were protected partially against viral challenge with virulent FHV. Relative efficacy of the vaccine, on the basis of reduction of clinical signs of disease, was 52%. Results were similar after FCV challenge, with relative efficacy of 63%. Vaccination did not prevent local mild infection or shedding of FHV or FCV.

    What are the risks of vaccinating cats?

    • Feline injection-site sarcoma – A rare but aggressive type of cancer with links to vaccinations, especially rabies, and feline leukemia vaccines.1 cat per 10,000 doses of vaccine administered.
    • Allergic reaction – Between 11-10 of every 10,000 cats vaccinated will experience an allergic reaction that may be mild and self-limiting or cause a life-threatening anaphylactic reaction. This is why I will only ever have a veterinarian vaccinate my pets, in case of immediate anaphylaxis.

    Is a cat titre test effective?

    The American Association of Feline Practitioners states the following:

    According to the report, most cats that have a positive result on a titer test for feline panleukopenia are immune to the disease. Titers for feline herpesvirus-1 and feline calicivirus “may not necessarily correlate well with protective immunity and should not be used to predict protection in the future.” Titers for feline leukemia virus and feline immunodeficiency virus “do not correlate with immunity and should not be used to determine the need for vaccination.”

    What pet owners do with that information comes down to recommendations from the cat’s veterinarian, who is the one who has the full history and background, as well as risk factors such as cats who are indoor only vs outdoors, the prevalence of a disease in a particular area, show cats and cats who go to boarding catteries.

    There is no argument that vaccinations save lives, and every cat should be vaccinated, how often is a discussion between client and veterinarian. Even if you and your veterinarian decide to switch from annual to triannual, it is still important that the cat visits once a year for a thorough health check.


    • Julia Wilson, 'Cat World' Founder

      Julia Wilson is the founder of Cat-World, and has researched and written over 1,000 articles about cats. She is a cat expert with over 20 years of experience writing about a wide range of cat topics, with a special interest in cat health, welfare and preventative care. Julia lives in Sydney with her family, four cats and two dogs. Full author bio