| Puppy/kitten series start | 6 to 8 weeks of age (American Animal Hospital Association guidelines) |
| Series completion age | 16 weeks (American Animal Hospital Association guidelines) |
| Rabies: legally required | Most US states (Varies by state and local ordinance) |
| Core adult booster interval | Every 3 years (most core vaccines) (AAHA Canine Vaccination Guidelines) |
| FeLV vaccine | Core for kittens; risk-based for adult cats (American Association of Feline Practitioners) |
Why vaccination timing matters
Puppies and kittens are born with some passive immunity passed through their mother's milk, but that protection fades within the first weeks of life. Vaccines step in to train the immune system before that window closes. Starting too late leaves young animals exposed; spacing doses too close together can blunt the immune response. The schedule your vet recommends is built around those biological realities, not arbitrary habit.
Vaccination also has a community dimension. When enough animals in a population are immune, diseases spread less easily, which protects those who cannot be vaccinated for medical reasons. This is the basis for the general guidance that keeps shelter populations and dog parks safer.
For a broader look at preventive care, see what vets check during a routine visit and how vaccines fit into the annual wellness picture.
Core vaccine
A vaccine recommended for all animals of a species regardless of lifestyle, because the targeted disease is severe, widespread, or a public health concern.
Non-core vaccine
A vaccine given only when an animal's specific circumstances, such as outdoor access or regional disease risk, make it appropriate.
Titer test
A blood test that measures the concentration of antibodies against a specific disease to assess whether existing immunity is still adequate.
Passive immunity
Temporary protection against disease that a newborn animal receives from its mother through colostrum (first milk). It fades within the first weeks of life.
Booster
A follow-up dose of a vaccine given after the initial series to maintain protective immunity over time.
Core vaccines for dogs
Core vaccines are recommended for all dogs regardless of lifestyle, because the diseases they target are either widespread, severe, or transmissible to humans.
- Distemper, parvovirus, and adenovirus (DA2P or DHPP): Usually combined in one injection, this series begins at 6 to 8 weeks, with boosters every 3 to 4 weeks until the puppy reaches 16 weeks. A booster follows at one year, then every 3 years for most adult dogs.
- Rabies: Required by law in most US states. Given as a single dose at 12 to 16 weeks, then again at 1 year. After that, frequency depends on the vaccine formulation and local law, typically every 1 to 3 years.
Your vet will record each dose and issue a certificate, which shelters, groomers, and boarding facilities commonly require.
Core vaccines for cats
Cats share a similar structure of core and non-core vaccines, with a few disease-specific differences.
- Feline panleukopenia, herpesvirus, and calicivirus (FVRCP): The feline equivalent of the canine combination shot. Series begins at 6 to 8 weeks, with boosters every 3 to 4 weeks until 16 weeks, then at 1 year, then every 3 years.
- Rabies: Recommended for all cats by the American Association of Feline Practitioners, even for cats kept indoors, because exposure through open windows, escapes, or bat contact is possible. Schedule mirrors the dog protocol.
Cats have a documented association between certain injection sites and a rare tumor called finjection-site sarcoma. Vets now follow site-specific guidelines to lower that risk. If your cat develops a persistent lump at an injection site, contact your vet promptly.
Non-core vaccines: when they apply
Non-core vaccines are given based on a dog or cat's individual risk profile. The vet considers where the animal lives, how it spends time, and whether it contacts other animals.
| Puppy/kitten series start | 6 to 8 weeks of age (American Animal Hospital Association guidelines) |
| Series completion age | 16 weeks (American Animal Hospital Association guidelines) |
| Rabies: legally required | Most US states (Varies by state and local ordinance) |
| Core adult booster interval | Every 3 years (most core vaccines) (AAHA Canine Vaccination Guidelines) |
| FeLV vaccine | Core for kittens; risk-based for adult cats (American Association of Feline Practitioners) |
For dogs: Bordetella (kennel cough) is standard before boarding or group training. Leptospirosis is worth discussing if your dog swims in natural water or lives in a region where wildlife exposure is common. Lyme disease vaccine is relevant in tick-heavy areas of the US.
For cats: Feline leukemia virus (FeLV) vaccination is core for kittens and recommended for cats with outdoor access. Indoor-only adult cats are assessed individually.
See how parasite prevention works year-round for context on related risks like tick-borne disease, which can overlap with vaccine decisions.
Adult boosters and titer testing
After the initial puppy or kitten series, vaccine schedules shift to less frequent boosters. The 3-year interval for core vaccines in adult dogs and cats reflects evidence that immunity from modern vaccines persists well beyond one year for most animals.
Some owners and vets consider titer testing as an alternative to automatic re-vaccination. A titer test measures the level of antibodies in the blood for a specific disease. If the result shows adequate protection, the vet may defer that booster. Titer testing is most practical for core vaccines; it is not a replacement for rabies vaccination, which follows legal requirements regardless of titer results.
For new pet owners building their first health plan, First-Time Pet Owner Health Essentials covers vaccination alongside other foundational steps.
This article is for general educational purposes and does not replace the personalized guidance of a licensed veterinarian. Always consult your vet before making decisions about your pet's vaccination schedule.