Cat Vaccinations: Core vs Non-Core, the Kitten Course and Adult Boosters

Cat vaccinations fall into two groups: core vaccines, recommended for every cat, and non-core vaccines, given to individual cats based on their age, lifestyle, and risk. The core group protects against diseases that are widespread, severe, or dangerous to people; the non-core group is matched to whether your cat goes outside, mixes with other cats, or faces a specific local threat. Your vet builds the schedule around your cat from there.

This guide covers what the two groups contain, the kitten course, adult boosters, what indoor cats actually need, and the AAHA and AAFP guidance that most vets follow.

Core vaccines: what every cat needs

Core vaccines are the ones the American Association of Feline Practitioners recommends for every cat, regardless of lifestyle. For cats these protect against feline panleukopenia (a parvovirus that is often fatal), feline herpesvirus and feline calicivirus (the two main causes of cat flu), and rabies where it is present or legally required. The first three are usually given together as the combined FVRCP vaccine, so a single injection covers them. These count as core because the diseases are either very common, very serious, or, in the case of rabies, a risk to human life too.

Non-core vaccines: matched to your cat’s risk

Non-core vaccines are given only to cats whose circumstances justify them, not to every cat. The most important for many cats is the feline leukaemia virus (FeLV) vaccine: the AAFP recommends FeLV vaccination as core for all kittens, because their lifestyle is not yet fixed, then non-core for adults based on whether they go outside or live with FeLV-positive cats. Other non-core options, such as Chlamydia felis or Bordetella, are reserved for specific situations like multi-cat households or shelters. Your vet weighs each one against your cat’s real exposure rather than giving everything as standard.

The kitten vaccination course

Kittens need a course of injections, not a single shot, because the immunity they inherit from their mother fades over their first weeks and would block a single early vaccine. The course usually starts at about 6 to 8 weeks of age, with a second injection 3 to 4 weeks later and often a third, so it typically finishes at around 16 weeks. Until the course is complete, kittens should stay indoors and away from unvaccinated cats. We map the full timeline, including parasite and neutering milestones, in our kitten vaccination and vet schedule.

I still remember sitting in the waiting room with my first kitten, Pixel, in a carrier on my lap for that second appointment. The vet explained that the reason we were back so soon was exactly this fading maternal immunity, and that skipping the follow-up would leave a gap where she looked protected but was not. That stuck with me: the course only works if you finish it, even when the kitten seems perfectly healthy after the first jab.

Adult boosters: keeping protection topped up

After the kitten course, a cat needs a booster at around 1 year old, and then boosters at intervals set by the vaccine and the cat’s risk. Once that first-year booster is done, many core components are then boosted every 1 to 3 years rather than annually, while some non-core vaccines such as FeLV are given yearly for at-risk cats. This is why your cat still needs a yearly health check even in a year when no vaccine is due: the visit lets your vet review protection, weigh your cat, and catch quiet problems early. Healthy adult cats should see a vet at least annually, and senior cats every 6 months.

Indoor cats: what they still need

Indoor-only cats still need their core vaccines, even though their risk is lower. Feline panleukopenia virus is extremely hardy and can survive in the environment for months, so it can be carried indoors on shoes or clothing without any cat ever coming inside. Cats also escape, go into boarding, or visit the vet, where they may meet others. Your vet may decide a strictly indoor adult does not need the FeLV vaccine after kittenhood, but the FVRCP core course and its boosters still apply. The decision belongs with your vet, not with a blanket indoor-versus-outdoor rule.

How vaccines fit the wider prevention plan

Vaccination is one part of preventive care, not the whole of it. Vaccines guard against infectious viral and bacterial diseases; they do nothing against parasites, which is a common point of confusion. Fleas, ticks, and worms are handled separately with regular treatments, covered in our guide to fleas, ticks, and worms in cats. Together with a complete diet, dental care, and regular check-ups, vaccination sits inside the broader routine we describe in the cat health guide. Serious vaccine reactions are uncommon; most cats show nothing more than brief tiredness or mild soreness for a day or so.

This guide is general information, not a diagnosis or a substitute for veterinary advice. The right vaccines and timing for your own cat depend on its age, health, and lifestyle, so always confirm the schedule with your own vet, who can examine your cat and knows its history.