Getting a new kitten is an exciting time. Finding a breeder, setting up the Insta account, hours spent “kitten-proofing” before then slowly resigning yourself to tiny claw marks on your furniture (and your legs!)… it’s a magical experience! A vet visit is usually on the cards, too, for a checkup and those mysterious “jabs”. Most kittens in the UK will receive a set of vaccines when they are young, but the latest PDSA PAW report suggests that around three in ten are still missing out on this vital protection. 

So what are these injections that vets recommend for kittens? What do they protect against? And – most importantly – do they work?

What Do We Vaccinate Kittens Against?

There are several different diseases that we recommend vaccinating kittens against. Your kitten will usually only need a single injection at each vet visit, but it will contain several different parts which help your kitten fight off these diseases. Each of these parts works a little differently, so we’ll look at each one in turn. 


The first disease on our list is a nasty one. Panleukopenia virus, also known as Feline Infectious Enteritis, is a serious illness, especially in young kittens. It causes a fever, severe vomiting, and sometimes watery diarrhoea. It also attacks the cat’s white blood cells (which are the infection-fighting cells), making it even harder for the body to fight off the virus. Without intensive treatment in a veterinary hospital, this will often lead to sepsis (blood poisoning) and death. Sadly, even with treatment, up to 3 out of every 4 cats infected with Panleukopenia will still die.  

Even more worryingly, Panleukopenia is a stubborn virus, and can survive out in the world for a year or more. This means your kitten could be infected by the virus that was left behind by another sick cat months before they were even born. Even if your kitten never leaves the house, they can still develop the illness from virus particles brought into the house by humans on objects such as coats, bags or shoes. 

The good news is that vaccination against Panleukopenia virus is highly effective. Studies reported by the immunologists at the WSAVA suggest that more than 98% of cats will be completely protected from becoming sick once they have finished their vaccination course.  

Calicivirus and Herpesvirus

These two viruses are often grouped together, and are often called “cat flu”. They cause symptoms such as sneezing, discharge from the nose, fever, sore eyes and a sore mouth and gums. In adult cats the symptoms may be relatively mild, but in young kittens these infections can be life-threatening.

These viruses are more fragile than Panleukopenia – Herpesvirus will only survive outside a cat for a day or so, and Calicivirus only up to a week – but kittens can still be infected by virus particles that are accidentally brought home on clothing. They can also be passed on by adult cats who may be infected without showing any symptoms, even if they have been vaccinated. 

The cat flu viruses infect cats in a different way to Panleukopenia. This makes it harder for your cat’s immune system to get rid of them completely, and means that scientists have not yet found a way to make a vaccine that offers protection that’s as good as the one against Panleukopenia.  

However, this does not mean that the current vaccines are useless. The protection that they offer means that once a kitten is vaccinated, if they catch one of these viruses they should only have very mild symptoms, or no symptoms at all. Since cat flu can be a serious, life-threatening illness in young cats, it is still important to give your kittens this protection. 

Leukaemia Virus

The final vaccination recommended for kittens in the UK is for Feline Leukaemia Virus, or FeLV. This is another nasty virus, which can cause a whole range of different symptoms. Around a third of cats who are infected with the Leukaemia virus will suffer with long-term effects from this. Most commonly, it will suppress the immune system (which means your cat can’t fight off other infections), and cause anaemia (low numbers of red blood cells) and certain types of cancer such as lymphoma or leukaemia. Sadly, the average lifespan of cats with long-term infections is only two to three years. 

Vaccines for Leukaemia virus are effective at preventing these long-term infections. Since they were introduced the number of infected cats in countries that use the vaccine has dropped, as has the number of cases of the cancers caused by these infections. However, the vaccines do not completely protect against milder, short term infections. These infections generally do not cause any symptoms, but it is possible for a blood test for Leukaemia virus to come back positive. 

Vaccination against the Leukaemia virus is not effective in cats who already have ongoing infections. The most common way for young kittens to become infected is via their parents, so if there is a risk that your kitten’s mother or father might have been infected, then your kitten should be tested for Leukaemia virus before being vaccinated. For more information and to find out if testing might be right for your kitten, speak to your vet.


If you like in a country where rabies is present, you should make sure your cat is vaccinated against it. Infection with rabies is fatal for humans as well as cats, so vaccination is critical to protect you and your family. Rabies vaccines are very effective at preventing infection. 

Why Don’t Vaccines Always Work?

All these vaccines are generally very effective, but sadly none of them work one hundred per cent of the time. We know some of the reasons that vaccines may fail, and so we can try to avoid them, but sometimes there is no clear cause. 

These are a few of the common reasons we can see vaccines fail:

Interfering Antibodies

The most common reason for a vaccine not to work is that the kitten still has some antibodies (infection-fighting proteins) from their mother, which can block the vaccine from working. These antibodies will naturally go away over time, so you should speak to your vet and make sure your kitten is the right age to be vaccinated. 

Jumping The Gun

A vaccine may also not work if the kitten is exposed to the illness too quickly after the vaccine is given. It takes some time for the kitten’s immune system to respond to the vaccine and build up their defences – cat flu vaccines, in particular, need a course of at least two injections, and it is a little while after the last injection before they are fully protected. Your vet should be able to tell you how long you must wait after the final vaccine until they are protected. 

Under The Weather

If your kitten is sick when they are given the vaccine, then their immune system may be “distracted” with fighting this other illness, and not respond properly to the vaccine. It is important to let your vet know if your kitten has had any signs of illness when you take them for their vaccinations. 

Is It Worth Vaccinating My Kitten?

Absolutely. No vaccine can offer perfect protection, but by getting your kitten vaccinated, you will reduce their risk of serious illness or even death. If you want to give your kitten the best start in life, then that should include getting them covered as soon as they are old enough.

For the practical details of when and how your kitten should be vaccinated, call your local vet practice.

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