Core vaccines go to every cat; noncore vaccines have to be earned by a particular cat's lifestyle. The whole decision reduces to 2 lists, 3 kitten dates, and a booster window of 1 to 3 years. The question worth asking is not whether vaccines work but which 4 facts about this cat you can state before the needle goes in.
The two lists and what sits on each
Core means the disease is common, serious, and hard to avoid. In cats that is 3 viruses shipped in 1 injection — feline herpesvirus-1 (FHV-1), feline calicivirus (FCV) and feline panleukopenia virus (FPV), sold as FVRCP — plus rabies wherever the law requires it. Noncore means risk depends on housing: feline leukemia virus (FeLV), Chlamydia felis, Bordetella bronchiseptica, and feline immunodeficiency virus (FIV). So 3 routine targets, 1 legal one, 4 optional ones.
FeLV is the product that changes category with age. Most feline panels call it core below 1 year and noncore for an adult that has lived indoors for 5 years with no positive housemates. That single age line explains most of the arguments owners have with their vet.
| Product | Category | Doses before 16 weeks | Months to first booster | Months thereafter, minimum | Months thereafter, maximum |
|---|---|---|---|---|---|
| FVRCP | Core | 3 | 12 | 12 | 36 |
| Rabies | Core where required | 1 | 12 | 12 | 36 |
| FeLV | Core under 12 months | 2 | 12 | 12 | 12 |
| Chlamydia felis | Noncore | 2 | 12 | 12 | 12 |
| Bordetella | Noncore | 2 | 12 | 12 | 12 |
| FIV | Not advised | 3 | 0 | 0 | 0 |
Three dates in the kitten series
Antibodies from colostrum protect a kitten and also block the vaccine, and they fade somewhere between 8 and 16 weeks. No test tells you the exact week, so the series is repeated instead of given once. The usual pattern is 3 doses: 1 at 6 to 8 weeks, 1 at 10 to 12 weeks, 1 at 14 to 16 weeks, with 2 to 4 weeks between doses.
A kitten that starts late at 12 weeks still gets 2 doses 3 to 4 weeks apart, and the final dose should land at 16 weeks or older. Stop at 12 weeks and you leave a 2 to 6 week window where the kitten is both unprotected and apparently vaccinated — the classic reason a 4 month old catches panleukopenia.
A 12 month booster follows 6 to 12 months after the last kitten dose. Skipping that one appointment is the most common reason a 2 year old cat shows no measurable response later.
Four checks before you agree
Most vets run the same 4 checks in the same order, and you can run them yourself before the appointment:
- Series status: how many doses, at what ages, and was the last one at 16 weeks or older.
- Exposure: indoor only with 0 escapes, or outdoor access, a home of 3 or more cats, boarding 2 or more times a year, a foster room.
- Law and travel: rabies intervals are local, often 1 year for the first certificate and 1 or 3 years after that; a 3 year product and a 1 year legal rule are 2 different things.
- Reaction history: swelling, vomiting or 1 day of lethargy within 48 hours of a past dose changes the plan — different site, splitting 2 products across 2 visits, or a pre-visit antihistamine.
When a noncore vaccine earns its place
FeLV: for cats under 1 year, for any cat with outdoor access, and for a cat moving in with a resident of unknown status. Test before vaccinating — a point-of-care antigen test reads in 10 to 15 minutes — then give 2 doses 3 to 4 weeks apart, boost at 12 months, then annually while the risk lasts.
Chlamydia felis pays off mainly in a cattery with repeated conjunctivitis: 2 doses 2 to 4 weeks apart, annual after. Bordetella suits cats that board 2 or more times a year. FIV vaccine exists in some countries and most vets skip it, because protection is partial and it muddies every antibody test for years afterward.
The 1 to 3 year window
After the 12 month booster, FVRCP and rabies are usually repeated every 3 years where a 3 year product is licensed, and every 1 year where it is not. FeLV stays annual while exposure continues. Antibody titers are a fair alternative for FVRCP in adult indoor cats: a positive FHV-1, FCV and FPV titer at a 1 to 3 year interval usually supports waiting, though no titer predicts rabies protection — the antibody titer guide walks through the cutoffs.
Records do as much work as intervals. Three items — last dose date, product name, lot number — settle most disputes at the next visit, and lot number is the only thing that helps if a batch causes a reaction.
Thirty minutes and three days after
Reactions cluster in 2 windows. Within 15 to 30 minutes: facial swelling, vomiting, collapse, so stay within 10 minutes of the clinic for that half hour. Between 2 and 48 hours: soreness, a 1 to 2 cm firm swelling, mild lethargy, eating 1 meal less than usual — that usually settles in 24 to 48 hours.
Call the vet if a swelling is still 2 cm or larger at 3 weeks, if any lump is present at 3 months, or if vomiting repeats more than 3 times in 24 hours. Ask the clinic to log the reaction against the lot number; a second reaction is treated more cautiously than a first, and this 3 day reaction checklist is the version to keep on the fridge.
What the schedule costs in visits
A kitten series is 3 visits plus 1 booster at 12 months: 4 appointments and roughly 90 to 150 minutes of clinic time across the first 14 months. A triennial adult needs 1 visit every 3 years, which is 3 visits per decade instead of 10. Whatever the price of a dose, the 16 week rule and the 12 month booster are the 2 items that decide whether the money bought protection.
Do this next
- Photograph the vaccination card today and note the 3 dates.
- Count the cats in the house and the escapes in the last 12 months; that is your FeLV risk score.
- Book the next dose at 16 weeks or later rather than 12.
- Set a reminder for 12 months after the final kitten dose.
- Keep 30 minutes of clinic waiting time after any injection.
Terms mentioned in this article
Frequently asked
Does an indoor-only cat need noncore vaccines at all?
Usually not for FeLV or Chlamydia, provided the cat has 0 escapes, lives with 1 to 2 stable negative cats, and never boards. Rabies still depends on local law, and a cat that travels 1 or more times a year or meets foster kittens should be reassessed at the 12 month booster rather than assumed low risk.
What if the kitten series was finished at 12 weeks instead of 16?
Add 1 dose now, at least 2 weeks after the last one, and count that as the series end. Maternal antibody interference is most likely between 8 and 16 weeks, so a series closed at 12 weeks leaves a real gap. Then keep the 12 month booster, and the cat is back on a normal 1 to 3 year schedule.
Can a titer replace the 1 to 3 year booster?
For FVRCP in a healthy adult indoor cat, yes in most practices: a positive FHV-1, FCV and FPV titer usually supports waiting another 1 to 3 years. Titers do not substitute for rabies vaccination where the law requires a certificate, and they are not validated for FeLV.