Vaccination is one of the most important things you will ever do for a kitten, and as a breeder it is one of your clearest duties to the cats you produce and the families who take them home. A well-timed vaccination course protects a kitten through the most vulnerable weeks of its life, stops outbreaks tearing through a cattery, and gives new owners a healthy, properly protected pet. This guide explains exactly what kittens are vaccinated against, when the injections are given in the UK, why the timing matters so much, and how vaccination fits into the wider job of raising a litter. It is written from a GCCF breeder and judge’s perspective, but the principles apply to any cat.
Why vaccinate kittens at all?
Kittens are born with some protection borrowed from their mother. While they are nursing, they take in antibodies through her milk — what vets call maternally derived antibodies, or MDA. This temporary immunity is a wonderful thing, but it fades over the first weeks of life, and the exact moment it disappears varies from kitten to kitten. There is a window, usually somewhere between six and twelve weeks, where the borrowed protection has worn thin but the kitten has not yet built its own. That gap is precisely when unvaccinated kittens fall seriously ill.
The diseases we vaccinate against are not minor. They are the infections that, before routine vaccination, regularly killed kittens or left survivors with lifelong problems. Vaccinating closes the gap, and because so many cats are vaccinated, it also keeps the overall level of disease in the population low — protection that benefits even those cats who, for medical reasons, cannot be fully vaccinated. For a breeder, there is a practical dimension too: a single unvaccinated kitten incubating cat flu can infect an entire litter, a queen, and the studs and kittens of anyone you have been in contact with.
What kittens are vaccinated against
In the UK, the standard “core” vaccines — the ones every cat should have — protect against three viruses, with a fourth very commonly added for kittens.
Feline panleukopenia (feline infectious enteritis)
Feline panleukopenia virus (FPV), also called feline infectious enteritis, is a parvovirus that attacks the gut and the immune system. It causes severe vomiting, bloody diarrhoea and collapse, and in young kittens it is frequently fatal. The virus is extremely hardy and can survive in the environment for months, which is why it can appear seemingly out of nowhere. It is the single most important reason no kitten should leave for a new home unprotected.
Feline herpesvirus and feline calicivirus (cat flu)
Feline herpesvirus (FHV-1) and feline calicivirus (FCV) are the two main causes of “cat flu” — the sneezing, runny eyes, mouth ulcers, fever and loss of appetite that can make a kitten miserable and, at worst, can be life-threatening. Herpesvirus, like cold sores in people, stays in the body for life and can flare up at times of stress, so a cat that recovers can still carry and spread it. Vaccination does not always prevent infection outright, but it dramatically reduces how severe the illness is.
Feline leukaemia virus (FeLV)
Feline leukaemia virus suppresses the immune system and is associated with anaemia and certain cancers. It spreads between cats in close, regular contact — mutual grooming, shared bowls, bites. In the UK, FeLV vaccine is often treated as core for kittens, because a young cat’s eventual lifestyle is rarely fixed at twelve weeks old and the consequences of infection are so serious. Cats who will genuinely live indoors with no contact with other cats may, on veterinary advice, drop FeLV at adulthood; but for kittens it is usually given as a sensible default.
There is one further vaccine — rabies — which is not needed for cats living in the UK but is required for international travel under an Animal Health Certificate or pet passport. It can be given from twelve weeks and is only relevant if a kitten is going abroad.
The UK kitten vaccination schedule
A kitten that has never been vaccinated needs a primary course of two injections, given three to four weeks apart. In the UK this is most commonly done at 9 weeks and 12 weeks of age, although your vet may start a little earlier or later depending on the practice’s protocol and the kitten’s circumstances.
- First injection (around 9 weeks): begins building the kitten’s own immunity to panleukopenia and cat flu, with FeLV usually included.
- Second injection (around 12 weeks): boosts and completes the primary course. A kitten is only considered properly protected after this second injection.
- Settling period (about a week): it takes roughly seven days after the final injection for full immunity to develop — which is exactly why kittens should not go to new homes immediately after the second jab.
- First booster: after the primary course, a booster keeps protection topped up. Modern guidance increasingly favours a six-month rather than a twelve-month first booster, then boosters at intervals appropriate to each disease.
Some kittens, particularly those from queens with very high antibody levels, may need a third injection at around 15–16 weeks to be sure the vaccine has “taken”. Your vet will advise whether this applies. After the first year, the core cat-flu and panleukopenia components generally need boosting no more often than every three years, while FeLV protection is shorter-lived and is boosted more frequently. Your vet will set a tailored booster plan rather than vaccinating everything every year by default.
Why the timing matters so much
The reason vaccinations are not simply given as early as possible comes back to those maternal antibodies. While a kitten still has high levels of borrowed antibody, that antibody can actually “block” a vaccine from working — the immune system mops up the vaccine virus before the kitten learns to respond to it. Give the injections too early and you may end up with a kitten that looks vaccinated on paper but has not actually built protection. This is why the second injection is timed for around twelve weeks, by which point maternal antibody has usually faded enough for the vaccine to do its job.
This single piece of biology explains one of the most important rules in pedigree breeding: the GCCF guidance that kittens should not leave for new homes before 13 weeks, with the full vaccination course completed at least seven days beforehand. It is not bureaucratic box-ticking — it is the difference between a kitten that is genuinely protected and one that only appears to be. You can map all of these dates from the mating date using our litter planner.
Do indoor-only cats need vaccinating?
Yes — this is one of the most common questions new owners ask, and the answer is firmly yes. Even a cat that never sets a paw outdoors needs protection against cat flu and panleukopenia. Panleukopenia virus is so tough and so infectious that it can be carried indoors on shoes, clothing and hands; cat flu viruses spread the same way. An indoor cat may, with veterinary agreement, not need the FeLV component once it is an adult, because FeLV requires close cat-to-cat contact. But the core vaccines are not optional just because a cat lives inside. Vaccination is also usually a condition of using a boarding cattery, entering a show, or travelling, so even a homebody benefits from being up to date.
Are vaccines safe? Side effects explained
Vaccines are very safe, and the risks of the diseases they prevent vastly outweigh the risks of the injections. Most kittens show nothing at all, or at most are a little quiet and sleepy for a day, perhaps with a slightly tender spot where the injection went in. This is the immune system doing its job and settles quickly. Occasionally a kitten runs a mild temperature or goes off its food briefly.
Serious reactions are rare. A genuine allergic reaction — facial swelling, vomiting, difficulty breathing shortly after the injection — needs immediate veterinary attention, but it is uncommon. There is also a very rare association between injections and a type of tumour at the injection site; it is rare enough that it does not change the overwhelming case for vaccinating, and modern vaccines and injection-site protocols are designed to minimise it. If you are ever worried after a vaccination, ring your vet — they would far rather hear from you.
What vaccination costs
Prices vary widely between practices and regions, so always check with your own vet, but as a rough guide a primary kitten course typically costs somewhere in the region of a single mid-range vet visit, with annual boosters costing less. Many practices offer health-care plans that spread the cost of vaccinations, flea and worm treatment and check-ups across the year. For a breeder, the cost of the first vaccination is simply part of the cost of producing a kitten properly — and a fully vaccinated kitten is far easier to home with confidence.
A breeder’s responsibilities
As the breeder, you are responsible for getting the kittens’ vaccinations under way and for being honest about what has been done. Good practice — and the standard expected of GCCF and responsible breeders — is that kittens have at least started, and ideally completed, their vaccination course before they leave, that the new owner receives the vaccination card or certificate from the vet, and that you explain when the next booster is due. Kittens should also be microchipped (a legal requirement in England by 20 weeks, and something responsible breeders do before the kitten leaves) and registered.
Vaccination sits alongside the other early-life jobs of raising a litter: weaning, worming, socialisation and health checks. For the wider picture, see our complete guide to breeding cats, and point new owners to the new kitten checklist so they know what to ask and what to expect. If you are managing lots of buyer questions about vaccination and collection dates, our guide to dealing with kitten enquiries will help.
Plan the whole litter timeline
Enter the mating date and our free Litter Planner maps the vaccination dates and the earliest day the kittens can leave.
Kitten vaccinations: FAQ
When do kittens get their vaccinations in the UK?
The primary course is two injections, usually at 9 and 12 weeks of age, given three to four weeks apart. A kitten is only fully protected about a week after the second injection.
How many vaccinations does a kitten need?
Two injections for the primary course, followed by a booster. Some kittens need a third injection at around 15–16 weeks, and all cats need ongoing boosters as advised by the vet.
Can a kitten go outside before it is fully vaccinated?
No. A kitten should not have unsupervised outdoor access or mix with unknown cats until about a week after the second injection, when immunity has developed.
Do house cats really need vaccinating?
Yes. Cat flu and panleukopenia can be carried indoors on clothing and shoes, so indoor cats still need the core vaccines. FeLV may be dropped for a truly indoor adult on veterinary advice.
My kitten is sleepy after its jab — is that normal?
A quiet day and a slightly sore injection site are normal and pass quickly. Contact your vet if you see facial swelling, repeated vomiting, breathing difficulty, or if the kitten seems genuinely unwell.
This guide is general information for breeders and owners, not veterinary advice. Vaccination protocols vary, so always follow your own vet’s recommendations for your kittens.
