Cat - Vaccinations

Vaccination is a common and important part of a preventative healthcare regime for cats.  The introduction of vaccination has significantly decreased the number of cats that suffer from and die of many infectious diseases.

Currently cats are commonly vaccinated against the following diseases:-

• Feline panleukopenia (sometimes called feline infectious enteritis, feline parvovirus). This is an uncommon disease that causes a severe and often fatal gastroenteritis (vomiting and diarrhoea) and destruction of the cells in the blood.  Vaccination provides a high level of long lasting protection.
• Feline herpes virus type 1 and Feline calicivirus (sometimes called cat flu or FHV-1/ FCV).  'Cat flu' is not usually very serious and it is a common disease in unvaccinated cats. However in some cats (often very young kittens) it can cause a life threatening infection and in older cats it can cause long-term eye and nose problems.  Vaccination against these two viruses is less effective than vaccines against panleukopenia as immunity is not long lived.  See handout on Upper respiratory tract infections.
• Feline leukaemia virus (often abbreviated to FeLV).  This virus can cause many different types of problems including suppression of the immune system, various types of tumours (cancer) and destruction of the cells in the blood.  Whilst the majority of cats that meet this virus are able to combat this infection a significant proportion (about 30%) will become persistently infected by the virus.  Persistently infected cats will die from the infection but because the virus tends to take many months before it causes disease infected cats can appear completely normal.  For this reason your veterinary surgeon may suggest that your cat has a blood test to make sure that it is not infected before vaccination.  Current vaccines provide a good level of protection and do not interfere with routine testing for the virus in breeding colonies.  See handout on Feline leukaemia virus.
• Chlamydophila felis.  This tends to be a particular problem in households with multiple cats or in rescue shelters.  This bacteria most commonly causes conjunctivitis (sore eyes), though sometimes it is associated with respiratory (breathing) disease and infertility in queens.  Infection in colonies of cats can last for long periods as cats re-infect each other so vaccination can help prevent infection becoming established.  See handout on Feline chlamydiosis.

• Rabies.  This vaccination is only required for cats that are travelling abroad or have entered the UK from abroad.  See handout on PETS.

How do vaccines work?

If a cat meets an infection the body's immune system will respond and fight that infection, but in the process the cat may succumb to disease.  When a cat is given a vaccination against a particular disease the body's immune system responds in the same way but the cat will not get sick.  This means a cat will be protected without having to get symptoms of the disease.  The vaccination leads to the production of antibodies that can directly neutralise infection and activate other cells to kill the infection.  The immune system then 'remembers' the disease it is vaccinated against so if it meets it in the future will be protected.

It is important to realise that a vaccine cannot stop a cat being infected.  This is impossible as just like us, cats meet lots of different pathogens (e.g. viruses and bacteria) all of the time. However, if a cat meets a pathogen it is vaccinated against then if it gets infected it will either not get signs of disease or they will be much less severe than if they had not been vaccinated.

What is the difference between the various types of vaccine?

The major types of vaccine that are produced for use in cats include:

1. Modified live vaccines - these vaccines contain live organisms that are weakened (attenuated) so that they do not produce disease but will multiply in the cat's body and stimulate the immune system. It is not advisable to use modified live vaccines in pregnant queens or cats whose immune system is not working properly e.g. cats infected by feline immunodeficiency virus (FIV).  See handout on Feline immunodeficiency virus.
2. Killed (inactivated) vaccines - these vaccines are prepared using fully virulent organisms that have been killed by chemicals, UV light or radiation.  Most killed vaccines contain a chemical (adjuvant) that helps stimulate a better immune response.
3. Subunit vaccines - these are dead vaccines in which the pathogen (virus/bacteria) has been broken apart and only certain parts are included in the vaccine.  In some cases this is achieved by using genetic engineering techniques.

4. Vectored vaccines - these are the newest types of vaccines.  Small amounts of the genetic material from the pathogen are inserted into a different harmless virus (so the harmless virus 'looks like' the pathogen)and made into a vaccine. These vaccines do not contain an adjuvant.

When should my kitten be vaccinated?

In most situations kittens are vaccinated for the first time around 9 weeks of age with a second dose 3-5 weeks later. It is important that a kitten receives both vaccinations to stimulate the immune system adequately. A kitten will not be fully protected until 7-10 days after the second vaccination.  Under specific circumstances your veterinary surgeon may advise an alternative regime.

How often should booster vaccinations be given?

After the initial course of vaccination cats will need regular boosters in their life to maintain protection, the frequency of boosters depends on the type of vaccine given, the lifestyle of your cat and the disease we are trying to protect against. In most situations booster vaccination is generally carried out yearly, although some panleukopenia vaccines can now be given once every three years. Your vet will advise on the best regime for your cat.

Will vaccination always protect my cat?

Vaccination will protect the vast majority of cats from clinical signs of disease but under some circumstances vaccine breakdowns will occur.  There are many reasons for this including:-

1. Variations between different strains of viruses - some viruses (e.g. FCV, one of the cat flu viruses) have lots of different strains or types. Each vaccine only contains one or sometimes two types or strains and the cat will produce antibodies against that particular strain. The protection provided by the strains in the vaccine do not necessarily protect against all of the different strains that exist.  Occasionally your cat may therefore get signs of cat flu if they meet one of the strains not covered by the antibodies produced by the vaccination.
2. Maternally derived antibodies - when a kitten is born it is protected in its early life by antibodies passed from the queen in the first milk (colostrum).  These antibodies may interfere with the vaccination and stop the immune response.  The amount of colostral antibodies that each kitten receives and the length of time they last in the body is variable hence the age at which a kitten can be successfully vaccinated will also vary.  This is part of the reason that two injections are given in the primary course.
3. The cat was not healthy at the time of vaccination - illness due to another disease or 'stress' at the time of vaccination can prevent a cat responding properly to a vaccine. This is why your vet will examine your cat thoroughly prior to vaccinating it to make sure it is well, and why it is often advised that a kitten is allowed to settle into its new home for 5-7 days before the first vaccinations are given.

It is important that if you think your cat has contracted an infection for which it is vaccinated against that you speak to your veterinary surgeon. If appropriate your vet will then perform the necessary tests to try and establish why vaccination has failed to be protective in your cat.

What are the risks of vaccination?

Your veterinary surgeon will be able to advise you about the potential risks following vaccination. It can be quite common for a cat/kitten to be quiet and sleepy after vaccination but if you are concerned about your cat it is important to seek advice from your veterinary practice.

REGULAR VACCINATION IS AN IMPORTANT PART OF ROUTINE HEALTH CARE FOR YOUR CAT AND HELPS TO ENSURE YOUR CAT REMAINS FIT AND WELL.