Most pet owners accept vaccination as a routine and necessary part of cat care. It is recommended for all cats to be vaccinated against cat flu, as well as feline parvovirus, and the aim of these injections is fairly simple: to prevent disease. However, nothing is infallible and being vaccinated doesn’t always mean full protection. So how good are the cat flu vaccinations at their job? Read on to find out more!

Table of contents

What is a vaccination?

Vaccines are a safe, simple and effective way to protect cats against certain diseases without them even needing to come into contact with them. Vaccines mimic diseases, and therefore train the body’s immune system with how to defend against certain disease-causing organisms, such as viruses. Immune systems are good at remembering how to respond to certain threats. So a vaccination annually or every few years is enough to keep the system primed and ready for attack. 

Vaccines not only protect the individual cat; they also protect other cats by the concept of herd immunity. The more cats that are vaccinated, the less these diseases will circulate amongst the population, reducing levels of disease. 

What vaccines do cats need?

The ‘core’ set of cat vaccines cover feline calicivirus and herpesvirus (the cat flu viruses) and feline parvovirus. Usually, feline leukaemia is included as an additional vaccine. Kittens will have two vaccinations, a few weeks apart, and then adult cats will require a yearly booster. 

The World Small Animal Veterinary Association (WSAVA) has a Vaccination Guidelines Group (VGG) who advise on current research around vaccinations: what to give and when. The VGG’s current recommendations1 is for all kittens to receive an initial course of the three core vaccines, with most adult cats receiving a booster vaccination every year for cat flu and every three years for feline parvovirus. The feline leukaemia virus is given as a primary course to kittens, and then again every 2-3 years, dependent on risk.

Why do we vaccinate against cat flu?

Cat flu is an extremely common respiratory disorder caused by two viruses: feline calicivirus (FCV) and feline herpesvirus (FHV) – or both! It presents with a range of symptoms including sneezing, coughing, mouth and eye ulcers, discharge from the nose, drooling, fever and lethargy. It is highly infectious through contact with nasal/eye discharge or sneeze droplets, but also through the environment such as through sharing bedding or food bowls, or carried on the clothing and hands of human carers. Cats can also continue to shed and spread the virus even after they have recovered. Many cats will recover, but it can cause severe disease especially in kittens. There are no specific treatments and cats can be left with lasting health problems. 

Vaccination is recommended as the viruses are both very common and highly infectious. Vaccination reduces disease in individual cats, but can also help to prevent outbreaks in areas with high populations of cats, such as rescue centres, catteries and even homes with multiple pets. 

Do vaccines really work?

As with all medications, vaccines vary as to how effective they are, with some being extremely good at preventing disease, and others having lower levels of success. 

Studies have shown that cats vaccinated against the cat flu viruses will still be able to be infected by the viruses, but that the disease symptoms will be much less severe2. A small study in 20093 found that the efficacy of the vaccines, based on reduction of symptoms, was around 53% for FHV and 63% for FCV. These figures don’t sound very promising, but it is worth remembering that the main aim of vaccination is to reduce disease, and prevent spread. 

Cats who are vaccinated generally show much less severe symptoms, and the vaccines should also help prevent these highly infectious diseases from spreading through a population. Cats infected with feline herpesvirus can become carriers and shed the virus after recovery, but vaccination may reduce this shedding, as well as protecting against disease.4 

Multiple strains

There are multiple strains of both FHV and FCV. The vaccines are designed to protect against a variety of strains, but some very nasty types of cat flu can still occur in vaccinated adults.5 Recovery from both FHV and FCV doesn’t induce enough protection from being re-infected, so cats are recommended to be vaccinated even if they have already had cat flu.6,7 

The VGG group recommend vaccination every 1-3 years for FHV and FCV. There is some evidence that protection starts to wane after a year, but partial protection remains for up to three years.2 The VGG therefore recommend three-yearly boosters for low-risk cats, such as a cat living alone, indoors, and with no visits to catteries or similar environments. Higher risk cats, such as those living in multi-cat households with outdoor access, or who visit catteries, should be vaccinated annually.1 

Summing up

We all wish that there was a magical injection that prevented our beloved pets from ever catching an infectious disease. Sadly, there isn’t – yet! – but as pet owners, we can still do what we can to protect our cats. The cat flu injections are not perfect, and fully vaccinated cats can still become infected with both feline calicivirus and feline herpesvirus. However, it is likely that if they are infected, their symptoms will be much milder, reducing the likelihood of severe disease and chronic health problems. Vaccination also reduces the spread of infection, potentially protecting other cats. If you’d like to know more about vaccinations for your cat, speak to your veterinary surgeon for more information. 

References:

  1. M. J. Day, M. C. Horzinek, R. D. Schultz, & R. A. Squires (2016) ‘WSAVA VGG Guidelines for the Vaccinations of Dogs and Cats’ Journal of Small Animal Practice 57
  2. Jas, D., Frances-Duvert, V., Vernes, D. (2015) Three-year duration of immunity for feline herpesvirus and calicivirus evaluated in a controlled vaccination-challenge laboratory trial. Veterinary Microbiology 177, 123-131
  3. Scott, F. W. & Geissinger, C. M. (1999) Long-term immunity in cats vaccinated with an inactivated trivalent vaccine. American Journal of Veterinary Research 60, 652-658
  4. Gaskell, R., Dawson, S., Radford, A. & Thiry, E. (2007) Feline herpesvirus. Veterinary Research 38, 337-354
  5. Pedersen, N. C., Elliott, J. B., Glasgow, A. (2000) An isolated epizootic of hemorrhagic-like fever in cats caused by a novel and highly virulent strain of feline calicivirus. Veterinary Microbiology 73, 281-300
  6. Thiry, E., Addie, D., Belak, S., Frymus, T., Radford, A. (2009) Feline Herpesvirus infection. ABCD guidelines on prevention and management J Fel Med Surg 11(7)
  7. Radford, A., Addies, D., Belak, S., Thiry. E. (2009) Feline calicivirus infection. ABCD guidelines on prevention and managementJ Fel Med Surg 11(7)