Your cat has never left the apartment. It has never met another cat. So the vaccination question feels like it answers itself.
It does not. A cat that stays indoors still lives in a building where other animals move through ceiling voids and drains. Thai law still applies to it. And the virus that kills the most unvaccinated kittens in this country does not need two cats in a room to spread. It travels on shoes.
What a vaccine actually does
A vaccine is not medicine. It treats nothing.
It is a rehearsal. The injection carries a version of a virus that has been weakened or killed: enough of the shape to be recognised, not enough to cause the disease. The immune system meets it, builds antibodies against it, and keeps the blueprint. When the real virus arrives eight months or four years later, the response is already written. The cat clears it before it becomes an illness.
That is the entire mechanism. The rest of this article is about which viruses are worth rehearsing for, and when.
Rabies is not a preference in Thailand
Thai law requires cat owners to vaccinate against rabies. It is a legal obligation, not a veterinary recommendation, and there is no indoor exemption written into it.
The reason is the carrier list. Rabies in Thailand circulates mainly through dogs, but bats and rodents carry it too, and both of those get into buildings. A bat in a stairwell. A rat in a ceiling void. A cat that hunts whatever moves. The exposure route does not require your cat to go out. It requires something else to come in.
Rabies is also the only disease on this list with no treatment once symptoms appear. Not in cats, not in people. Every case ends the same way. That is why it sits in legislation while the others sit in guidelines.
The three viruses in the core vaccine
The core vaccine usually appears on the record card as FVRCP. One injection, three viruses, and every cat needs it regardless of lifestyle.
Feline panleukopenia
Panleukopenia is a parvovirus, and it is the reason kitten vaccination schedules exist at all.
It attacks fast dividing cells. The bone marrow first, then the lining of the gut. White cell counts collapse. The gut wall stops holding. A kitten can go from bright to dead in under three days.
What makes it worse is the virus itself. Panleukopenia survives in the environment for months and shrugs off most household disinfectants. It does not need a sick cat to be present. It needs a surface, a shoe, and a person who walked past a market where a sick cat was lying. That is how it reaches a cat that has never left the fourteenth floor.
In unvaccinated kittens the death rate is severe. In vaccinated cats the disease is close to absent. Very few interventions in feline medicine produce a gap that wide. The Cornell Feline Health Center lists it among the most serious infectious diseases a cat can face.
Herpesvirus and calicivirus, the two halves of cat flu
Cat flu is not one disease. It is two viruses producing a similar picture: sneezing, streaming eyes, ulcers in the mouth, a cat that stops eating because it can no longer smell its food.
The vaccine here works differently from the panleukopenia component. It does not reliably stop infection. It reduces severity, shortens the episode, and keeps a mild illness from becoming a hospital admission. That is a lower bar than sterilising immunity, and it is still worth having.
Herpesvirus has one extra property owners should know about. Once a cat is infected, the virus does not leave. It goes latent in nerve tissue and reactivates under stress: a house move, a new cat, a boarding stay. A vaccinated cat that carries herpes will still flare. It will flare less, and less severely.
Feline leukaemia, the one that depends on your household
Feline leukaemia virus does not travel through air or across surfaces. It moves through prolonged, intimate contact between cats: mutual grooming, shared bowls, bite wounds. It suppresses the immune system, and cats that stay persistently infected tend to have shortened lives.
Current feline vaccination guidance treats FeLV as core for kittens and optional for adults. That split is deliberate. Kittens are far more susceptible to persistent infection than adult cats, and no owner can promise where a kitten will be living in three years. So the kitten gets it.
The adult decision is a household question. A single indoor cat with no contact with other cats, no outdoor access and no plans to add a second cat is a reasonable place to stop. A multi cat home, a cat that uses the balcony, or a home that fosters is not.
Test before vaccinating. The vaccine does nothing for a cat that is already infected, and knowing the status changes how the whole household should be managed. The WSAVA vaccination guidelines set out the same core and non core split used by vets worldwide.
The kitten schedule, and why the last dose matters most
A kitten is born with borrowed immunity. Antibodies arrive through the mother's first milk and protect it through the first weeks of life. Those antibodies fade on their own schedule, and nobody can see the moment they go.
Here is the problem that creates. While maternal antibodies are still circulating, they neutralise the vaccine exactly as efficiently as they neutralise the virus. A vaccine given too early does nothing at all. It only looks like it did something.
That is why the kitten series is a series and not a single shot. Vaccination starts at six to eight weeks and repeats every three to four weeks until the kitten is at least sixteen weeks old. The doses in the middle are insurance. The final dose, given after maternal antibodies have certainly gone, is the one that actually immunises.
Owners who stop at twelve weeks because the kitten already had two are the ones who lose kittens to panleukopenia. The count is not what protects. The age at the last dose is.
After the series, a booster at around one year, then core vaccines every one to three years depending on the product and the cat. Rabies follows whatever interval Thai law and the vaccine label require.
The risks, stated honestly
Vaccines are not free of consequence, and pretending otherwise is how owners end up distrusting the whole subject.
Most reactions are mild and brief. A day of low energy, a slightly sore leg, a cat that sleeps more than usual and eats less. It resolves without treatment.
Allergic reactions happen and are rare. Facial swelling, vomiting or collapse within minutes to hours of the injection is an emergency, and it is the reason vets ask owners to wait a short while at the clinic rather than leaving straight away.
The rarest one is a tumour at the injection site, called a feline injection site sarcoma. Published estimates put it somewhere in the region of one case per ten thousand to one per thirty thousand doses given. It is the reason vets now inject low on a limb or in the tail rather than between the shoulder blades. A tumour in a limb can be removed with clean margins. A tumour over the spine often cannot.
Put those numbers beside the alternative. Panleukopenia in an unvaccinated kitten is not a one in ten thousand event. It is a common one, and it is usually fatal. The comparison is not vaccine risk against zero risk. It is vaccine risk against disease risk, and the gap is not close.
What this looks like at a working cattery
Pau and Sun run Bangkok Cats, a world championship cattery, which means kittens leave for new homes across Thailand and overseas every year. There is no version of that operation where vaccination is optional. Kittens complete the full series to sixteen weeks before they go anywhere, and the record card travels with them.
The pattern they see repeatedly in Thailand is not owners who refuse vaccines. It is owners who start the series and never finish it, because the kitten seems fine and the clinic is far away. The kitten is fine. It is also unprotected, and it stays unprotected until the last dose lands.
Common questions
Does an indoor cat really need vaccinating?
Yes. Rabies is required by Thai law with no indoor exemption, and panleukopenia is carried into homes on shoes and clothing rather than by cat to cat contact. The only vaccine that genuinely depends on lifestyle is feline leukaemia.
Which vaccines are legally required in Thailand?
Rabies. Thai law places the duty on the owner, not the vet, and it applies to cats as well as dogs. The core FVRCP vaccine is strongly recommended by every veterinary body but is not written into law.
When should a kitten have its first shot?
Between six and eight weeks, then a repeat every three to four weeks until the kitten is at least sixteen weeks old. Rabies is usually given from around twelve weeks. A vet will set the exact dates around the kitten's weight and health.
How often do adult cats need boosters?
A booster at about one year old, then core vaccines every one to three years depending on the product used and the cat's exposure. Rabies follows its own legal and label interval. Ask for the recheck date to be written on the record card.
Can a pregnant cat be vaccinated?
Most vets avoid vaccinating during pregnancy, particularly with modified live products. The better plan is to vaccinate before mating so the queen passes strong maternal antibodies to the kittens. Talk to your vet before breeding, not after.
Is it too late to vaccinate an adult cat that never had shots?
No. An adult with no vaccination history usually needs two doses three to four weeks apart, then normal boosters. There are no maternal antibodies left to interfere, so protection builds quickly.
