The Pet Vaccination Glossary: Terms Owners and Clinics Should Know
Reviewed for 2026, updated September 8, 2026.
Plain definitions for the words on your pet's vaccine record, plus answers to the questions we hear most often from owners, clinics, and groomers.
- Adjuvant
- An ingredient added to some killed or inactivated vaccines to strengthen the immune response. Adjuvanted vaccines have been discussed in feline medicine in relation to injection-site reactions, which is one reason some cat vaccines are formulated without them.
- Antibody titer
- A blood test that measures the level of antibodies against a specific disease. Titers are commonly used for canine distemper, parvovirus, and adenovirus, and for feline panleukopenia, to judge whether a booster is needed. Rabies titers are generally not accepted as a legal substitute for vaccination in the United States.
- Booster
- A repeat dose of a vaccine given after the initial series to maintain protection. Boosters are typically given about one year after the puppy or kitten series and then at intervals set by the product label, often one or three years.
- Bordetella
- A bacterium that is one of the main causes of kennel cough in dogs. The vaccine is non-core but is required by most boarding, daycare, and grooming facilities, some of which ask for a dose within the previous six months.
- Calicivirus
- A common feline respiratory virus covered by the FVRCP combination vaccine. It causes upper respiratory signs and mouth ulcers and spreads easily in shelters and multi-cat homes.
- Canine influenza
- A contagious respiratory virus in dogs. The vaccine is non-core and is usually recommended for dogs that board, attend daycare, or live in areas with recent outbreaks.
- Core vaccine
- A vaccine recommended for every dog or cat regardless of lifestyle, because the disease is severe, widespread, or a threat to people. For dogs the core set is rabies and DHPP; for cats it is rabies and FVRCP, with feline leukemia often treated as core for kittens.
- DHPP (DAPP)
- The combination vaccine for dogs covering distemper, hepatitis (adenovirus), parvovirus, and parainfluenza. Clinics may write it as DHPP, DAPP, DA2PP, or DHLPP when leptospirosis is included in the same shot.
- Distemper
- A serious, often fatal viral disease of dogs that affects the respiratory, digestive, and nervous systems. It is prevented by the core combination vaccine and remains a risk for unvaccinated puppies.
- Due date
- The date by which the next dose of a vaccine should be given, calculated from the date of the last dose and the interval on the product label. The due date is the anchor for every reminder, which is why it must be recorded at the time of vaccination.
- Duration of immunity
- How long a vaccine is expected to protect an animal. It is established by the manufacturer for the product label, and legal requirements for rabies follow the label interval, typically one or three years.
- Feline leukemia (FeLV)
- A retrovirus spread between cats through close contact such as grooming and shared bowls. Current guidelines commonly recommend the vaccine for all kittens and for adult cats with outdoor access or exposure to cats of unknown status.
- FVRCP
- The feline combination vaccine covering feline viral rhinotracheitis (herpesvirus), calicivirus, and panleukopenia. It is the core combination shot for cats and is given as a series to kittens.
- Health certificate
- A document signed by a veterinarian stating that an animal is healthy and, usually, currently vaccinated. It is often required for interstate travel, air travel, and some boarding facilities, and it is not the same document as a rabies certificate.
- Intranasal vaccine
- A vaccine given as drops in the nose rather than by injection, commonly used for Bordetella and some other respiratory vaccines. It stimulates a local immune response in the airways, and its booster interval may differ from the injectable form.
- Lapse
- A vaccine whose due date has passed without a new dose being given. A short lapse on a well-vaccinated adult is usually low risk, while a lapsed rabies vaccine can carry legal consequences if the pet bites or is exposed to wildlife.
- Lead time
- How far before the due date a reminder is sent. Typical lead times run from two to six weeks so the owner can secure an appointment before the vaccine expires.
- Leptospirosis
- A bacterial disease spread through water and soil contaminated by wildlife urine that can affect dogs and people. The vaccine has traditionally been classed as non-core, though some current guidelines recommend it for most dogs, and it is boosted annually.
- Lot number
- The manufacturer's batch identifier for a vial of vaccine. Clinics record it with each dose so a product can be traced if there is a manufacturer recall or an adverse reaction.
- Lyme disease
- A tick-borne bacterial infection. The canine vaccine is non-core and is recommended in regions where the disease is common and for dogs with regular tick exposure.
- Maternal antibodies
- Protective antibodies a puppy or kitten receives from its mother through colostrum. They fade unpredictably and can block early vaccines, which is why the initial series involves several doses until at least sixteen weeks of age.
- Non-core vaccine
- A vaccine recommended only for animals whose lifestyle, region, or exposure puts them at risk. Examples include Bordetella, leptospirosis, Lyme, and canine influenza for dogs, and feline leukemia for adult cats.
- Panleukopenia
- A highly contagious and often fatal feline viral disease, sometimes called feline distemper, that attacks rapidly dividing cells in the gut and bone marrow. It is covered by the FVRCP vaccine.
- Parvovirus
- A severe, highly contagious viral disease of dogs, most dangerous to puppies, that causes vomiting, diarrhea, and dehydration. Prevention through the core combination vaccine is far more reliable than treatment after infection.
- Practice management system
- The software a veterinary clinic uses for patient records, scheduling, invoicing, and, in most cases, automated reminders. Reminder accuracy depends on due dates being entered correctly in this system.
- Rabies certificate
- The signed document a veterinarian issues after a rabies vaccination, listing the animal, the product, the date given, and the date the vaccine expires. It is the proof most facilities and animal control officers will accept, and it is separate from the metal tag.
- Recall
- A veterinary term for the process of bringing patients back for services that are due, including vaccines. A recall program is the clinic-side name for a reminder system.
- Reminder cadence
- The sequence and spacing of reminder messages, such as an early notice, a due-date message, and an overdue follow-up. Multi-step cadences generally outperform a single message because they catch owners at different moments.
- Three-year vaccine
- A vaccine labeled to provide protection for three years after the booster, such as many adult rabies and core combination products. The three-year interval applies only after the initial series and the first booster, not to the first dose.
- Wellness exam
- An annual or semiannual veterinary visit for a healthy pet, during which vaccines are reviewed and boosted as needed. Pairing vaccines with the wellness exam is the simplest way to keep them on schedule.
Questions people ask
What vaccines does my dog legally need in the United States?
Rabies is the only vaccine required by law in most states and counties, and the required interval follows the product label and local rules, which may recognize one-year or three-year products. Other core vaccines such as DHPP are strongly recommended by veterinary guidelines but are generally not legal requirements. Boarding and grooming facilities may add their own requirements as a condition of service.
Do indoor cats need vaccines at all?
Yes. Rabies is legally required for cats in many jurisdictions regardless of whether they go outside, and indoor cats can still be exposed through a bat in the house or an escape. The FVRCP combination is recommended for all cats because the viruses it covers can be carried in on clothing and shoes. Non-core vaccines such as feline leukemia depend on actual exposure risk.
How long after a puppy's last shot is it safe to socialize in public?
Most veterinarians advise waiting until about one to two weeks after the final dose of the puppy series, which typically lands at sixteen weeks or later, before dog parks and other high-traffic places. Controlled socialization with known, vaccinated dogs is usually encouraged earlier. Your veterinarian's advice should reflect the local parvovirus situation.
What happens if my pet's rabies vaccine lapses?
Your pet is no longer considered currently vaccinated, which matters if it bites someone or is exposed to a wild animal, because quarantine and reporting rules for unvaccinated animals are stricter. Most facilities will refuse service until a booster is given. Contact your clinic promptly; a booster typically restores current status, though rules on how long that booster is valid vary by state.
How early should I schedule a booster before a boarding stay?
At least two weeks before check-in for most vaccines, and earlier if your dog needs a Bordetella dose that the facility wants given a set number of days in advance. Some facilities also require canine influenza, which may involve two doses several weeks apart the first time. Ask for the facility's written policy before you book.
Can I get vaccine records from a previous veterinarian or a shelter?
Usually yes. Veterinary clinics keep records for years and will typically release a vaccination history to the owner on request, and shelters and rescues generally provide whatever they administered at adoption. Ask specifically for dates given, product names, and due dates, and for a copy of the signed rabies certificate rather than a summary.
Why are some vaccines given yearly and others every three years?
The interval comes from the manufacturer's duration-of-immunity studies for each product and is printed on the label. Many adult core vaccines are labeled for three years, while most non-core vaccines and some rabies products are labeled for one year. Your veterinarian may also recommend a shorter interval for a pet with unusually high exposure.
Are clinic vaccine reminders reliable enough on their own?
For one pet at one clinic with a current phone number on file, they are usually adequate. They fail when the clinic's record has a missing due date, when your contact details are old, or when vaccines were given elsewhere. Keeping your own copy of the due dates, even just in a calendar, is a cheap safeguard.
What should I bring to prove my pet is vaccinated?
A signed rabies certificate and a printed vaccination history from the clinic showing each vaccine, the date given, and the date due. A metal rabies tag alone identifies the vaccination but does not show the expiration in a way most facilities accept. Many clinics can email the history so you can keep a copy on your phone.
Is it harmful to revaccinate a pet whose history is unknown?
For a healthy adult dog or cat, repeating core vaccines is generally considered safe and is the standard approach when history cannot be verified. Where a titer is available, such as for distemper and parvovirus in dogs, a veterinarian may use it instead. Rabies is usually repeated because titers do not satisfy legal requirements.
How do reminder apps calculate the next due date?
They start from the date a vaccine was given and add the interval for that product and life stage, such as two to four weeks between puppy doses, one year for the first booster, and one or three years after that. Good apps let you override the interval to match the exact date your veterinarian wrote down, since that record is the authority.
What is the difference between a rabies certificate and a rabies tag?
The certificate is the signed legal document listing the animal, the product, the date given, and the expiration date. The tag is a metal disc for the collar that shows the vaccination number and clinic, useful if a lost pet is found. Facilities and animal control rely on the certificate, not the tag, to confirm current status.
Should groomers refuse dogs with expired vaccines?
Most groomers set a written policy and stick to it, because inconsistent enforcement creates liability. A common approach is to require current rabies without exception, allow a short grace period for non-core vaccines with a signed acknowledgment, and reschedule the appointment once the owner confirms a booster is booked. Local rules on rabies may leave no room for a grace period.