Vaccination
The most effective way to prevent infectious disease, scheduled by core/non-core classification; cats have a unique injection-site sarcoma risk to watch for.
Core vs. Non-Core Vaccines
Core vaccines are recommended for all pets regardless of lifestyle; non-core vaccines are added based on environmental risk (going outdoors, frequent boarding, humid regions). Core vaccines for cats: feline panleukopenia (FPV), feline herpesvirus (FHV-1), feline calicivirus (FCV), and rabies — FeLV (feline leukemia) is also considered core for kittens under 1 year old; non-core: FeLV for cats over 1 year old, Chlamydia, and Bordetella, while the feline infectious peritonitis (FIP) vaccine isn't recommended due to insufficient evidence. Core vaccines for dogs: distemper, canine adenovirus, canine parvovirus, and rabies; non-core: leptospirosis, Bordetella (kennel cough), parainfluenza, Lyme disease, and canine influenza, while the canine coronavirus vaccine isn't recommended due to insufficient evidence.
How Well Vaccines Protect
Large-scale vaccination significantly reduces severe disease rates and is one of the most well-validated public health measures available. Dogs fully vaccinated with core vaccines (distemper, parvovirus, adenovirus) have around 98%+ protection; the feline FPV vaccine similarly offers about 98%+ protection, but FHV-1/FCV vaccines only offer about 60–70% protection against "developing disease" — vaccinated cats can still get infected, but symptoms are usually much milder. The rabies vaccine also protects human safety and is one of the few legally mandated vaccines.
Possible Side Effects
Common, mild side effects include low energy, reduced appetite, mild fever, and swelling at the injection site, which usually resolve on their own within a few days. Rare but more serious is anaphylactic shock (vomiting, difficulty breathing, facial swelling, collapse) — AAHA/AAFP guidelines estimate about 1–5 cases per 10,000 doses in cats, though estimates vary widely across studies (one UK database study found rates as low as 1 in 550,000), but all agree this is a very rare reaction. Cats also have a unique risk: feline injection-site sarcoma (FISS), a rare but malignant tumor reaction, occurring in roughly 1 in every 5,000–12,500 cats. If you feel a lump at your cat's injection site that meets any of these criteria — "still present after 3 months," "larger than 2 cm across," or "still growing after 1 month" — see a vet for evaluation as soon as possible.
Feline Injection-Site Sarcoma: Latency Period and Prevention
The "3 months / 2 cm / 1 month" rule mentioned above is a post-vaccination monitoring guideline, reminding owners to watch closely for new lumps during that window — but that doesn't mean most sarcomas actually grow within that short a time. Multiple studies show the actual latency period varies widely, from as short as 4 weeks to as long as 13–15 years; one large review found that most cases actually become a palpable lump 1–3 years after vaccination, and there's no single agreed-upon average figure. Another key point is that risk accumulates: studies have found that most confirmed cases had received repeated injections at the same site within the 3 years before onset. That's why vets generally recommend rotating injection sites each year and preferring the distal limbs (rather than the traditional spot between the shoulder blades) — this way, if a tumor does develop, it's easier to remove completely during surgery and there's a better chance of preserving the limb. This risk currently has clear research data mainly in cats; cases in dogs are extremely rare and mostly individual case reports, without statistics like those for cats, but rotating injection sites doesn't hurt for dogs either. If your cat or dog needs annual vaccinations, you can use Chronlo's "Vaccination Record" feature on the home screen to note the site each time (text or photo), so you know at a glance which side to switch to next time.
Recommended Vaccination Schedule
Kittens and puppies should start at 6–8 weeks old, with a booster every 2–4 weeks, and the final dose given at 16 weeks or older (maternal antibodies can interfere with vaccine effectiveness up to that age); a follow-up booster is given at 6 months old. After adulthood, core vaccines can be given as infrequently as once every 3 years, with protection lasting many years; non-core vaccines usually still need annual boosters. Some core vaccines can also be confirmed sufficient through "titer testing" — if levels are adequate, you can skip the scheduled booster, though rabies vaccination doesn't have this alternative due to legal requirements.
Want to track this over time? Try Chronlo
A chronic-care app for cats and dogs: daily logs, trend charts, blood test OCR, and medication reminders — all your pet's health data in one place.
Sources:
- AAHA/AAFP 2020 Feline Vaccination Guidelines
- WSAVA（World Small Animal Veterinary Association）Vaccination Guidelines
- UC Davis School of Veterinary Medicine
- ABCD（European Advisory Board on Cat Diseases）Guideline for Feline Injection-Site Sarcoma
- Wilcock et al. (2012), Canadian Veterinary Journal
- Srivastav et al. (2012), JAVMA
This site is for general reference only and is not a substitute for veterinary diagnosis. If your cat shows unusual signs, please see a vet promptly.