| Puppy series start age | 6–8 weeks (AAHA Canine Vaccination Guidelines) |
| Kitten series start age | 6–8 weeks (AAFP Feline Vaccination Guidelines) |
| Core dog vaccines | Rabies, Distemper, Parvovirus, Adenovirus (DHPP) (AAHA Canine Vaccination Guidelines) |
| Core cat vaccines | Rabies, Herpesvirus, Calicivirus, Panleukopenia (FVRCP) (AAFP Feline Vaccination Guidelines) |
| Typical adult booster interval | Every 1–3 years depending on vaccine (Varies by product label and state law) |
| Rabies — legal requirement | Required in most U.S. states for dogs; many states include cats (State regulations vary; confirm with your local authority) |
Core vs. Non-Core Vaccines: What the Terms Mean
Veterinary organizations classify pet vaccines into two broad categories: core and non-core. Understanding the difference helps families prioritize spending and have more informed conversations with their vet.
Core vaccine
A vaccine recommended for all pets of a given species regardless of lifestyle or geography. Core vaccines protect against diseases that are widespread, severe, or pose a public health risk.
Non-core vaccine
A vaccine recommended selectively based on a pet's individual risk factors such as geographic location, activities, or exposure to other animals. Non-core vaccines can be medically important for certain pets.
Booster
A follow-up dose of a vaccine given after the initial series to maintain or renew immunity over time. Boosters may be scheduled annually or every three years depending on the vaccine.
Titer test
A blood test that measures the concentration of antibodies in a pet's bloodstream. Titer results can indicate whether a previous vaccine generated sufficient immunity, though they do not replace legally required vaccines like rabies.
DHPP
A combination vaccine for dogs that covers Distemper, Hepatitis (Adenovirus), Parvovirus, and Parainfluenza in a single injection. It is a standard core vaccine administered during the puppy series and in adult boosters.
FVRCP
A combination vaccine for cats covering Feline Viral Rhinotracheitis (Herpesvirus), Calicivirus, and Panleukopenia. It is the primary core vaccine series for cats.
Core vaccines are recommended for virtually every dog or cat regardless of lifestyle. They protect against diseases that are widespread, severe, or transmissible to humans. Non-core vaccines are situational — your vet may recommend them based on where you live, your pet's activities, and exposure risk.
This distinction is not about which vaccines are "optional" in a casual sense. Non-core vaccines can be medically important for some pets. The label simply means they aren't universally necessary for all animals.
Core Vaccines by Species
The American Animal Hospital Association (AAHA) and the American Association of Feline Practitioners (AAFP) publish regularly updated guidelines that form the basis of most U.S. veterinary practice.
| Puppy series start age | 6–8 weeks (AAHA Canine Vaccination Guidelines) |
| Kitten series start age | 6–8 weeks (AAFP Feline Vaccination Guidelines) |
| Core dog vaccines | Rabies, Distemper, Parvovirus, Adenovirus (DHPP) (AAHA Canine Vaccination Guidelines) |
| Core cat vaccines | Rabies, Herpesvirus, Calicivirus, Panleukopenia (FVRCP) (AAFP Feline Vaccination Guidelines) |
| Typical adult booster interval | Every 1–3 years depending on vaccine (Varies by product label and state law) |
| Rabies — legal requirement | Required in most U.S. states for dogs; many states include cats (State regulations vary; confirm with your local authority) |
Dogs
- Rabies — required by law in most U.S. states; protects humans and animals alike
- Distemper — highly contagious viral disease affecting the nervous system
- Parvovirus — potentially fatal intestinal illness, especially in puppies
- Adenovirus (Hepatitis) — causes liver disease; often combined in a single DHPP shot
Cats
- Rabies — legally required in many states even for indoor cats
- Feline Herpesvirus and Calicivirus — major causes of upper respiratory infections
- Panleukopenia (Feline Distemper) — severe, often fatal disease; covered by the FVRCP combination vaccine
These combinations are typically given as a series starting at 6–8 weeks of age, then repeated at intervals through 16 weeks, followed by boosters in adulthood.
Non-Core Vaccines and When They Apply
Non-core vaccines address real risks — they're simply not universal. Your vet will assess your pet's individual exposure profile before recommending them.
Common non-core vaccines for dogs
- Bordetella (Kennel Cough) — often required by boarding facilities and groomers
- Leptospirosis — a bacterial disease spread through water and wildlife; relevant in rural or flood-prone areas
- Lyme disease — recommended in tick-heavy regions; pairs well with year-round parasite prevention (see our parasite prevention guide)
- Canine Influenza — relevant for dogs in high-contact environments like dog parks or daycare
Common non-core vaccines for cats
- Feline Leukemia Virus (FeLV) — strongly recommended for cats with outdoor access or multi-cat households
- Feline Immunodeficiency Virus (FIV) — limited availability; discuss with your vet based on lifestyle
- Chlamydiosis and Bordetella — considered for cats in shelters or dense multi-cat settings
FeLV Is Often Considered Core for Kittens
While Feline Leukemia Virus vaccine is technically classified as non-core by AAFP guidelines, it is strongly recommended for all kittens during their initial series before their lifestyle risk can be accurately assessed. Your vet may continue it based on your cat's ongoing outdoor access or contact with other cats. Discuss your cat's specific situation at each wellness visit.
How Vaccination Schedules Typically Work
Vaccination is not a one-time event. Schedules are designed around how long immunity lasts and how a pet's immune system matures.
3–4 weeks
Interval between puppy/kitten vaccine doses in initial series
Spacing allows the immune system to respond fully before the next dose is administered, per AAHA and AAFP guidance.
16 weeks
Age by which core puppy/kitten series is typically completed
Completing the series by this age helps ensure maternal antibody interference no longer limits immune response.
3 years
Maximum booster interval for some core adult vaccines
Certain DHPP and FVRCP formulations are labeled for 3-year re-administration in adult pets with documented prior vaccination.
Puppies and kittens
Young animals receive a series of vaccines spaced 3–4 weeks apart, typically from 6–8 weeks through 16 weeks of age. This series is necessary because maternal antibodies — passed through the mother's milk — can temporarily block vaccine effectiveness. Multiple doses ensure immunity develops as maternal protection wanes.
Adult boosters
After the initial series, most core vaccines shift to a 1-year or 3-year booster schedule depending on the vaccine type and product label. Rabies booster timing is governed by state law and the specific product administered. Non-core vaccines often require annual boosters.
Titer testing
Some owners ask about titer tests — blood tests that measure existing antibody levels — as an alternative to automatic re-vaccination. While titers can provide useful information, they don't replace all vaccines (particularly rabies, which is legally mandated). Discuss the pros, limitations, and cost trade-offs with your veterinarian.
Keeping consistent wellness appointments also supports overall health planning, including nutrition. Consider pairing vaccination visits with a diet review — resources like our feeding primer for new owners can help you prepare questions for your vet. Seasonal disease risks can also shift which non-core vaccines are timely — see seasonal health considerations for pets for a broader picture.
This article is for general informational purposes only and is not a substitute for veterinary advice. Always consult a licensed veterinarian to determine the appropriate vaccination plan for your specific pet.