Vaccine types

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Technologies employed in the manufacturing of vaccines for animals have expanded significantly over the past decade. Today in veterinary medicine the number of licensed vaccines continues to grow, driven largely by the need to protect dogs and cats against emerging pathogens, enhance vaccine safety, and improve immunogenicity of existing vaccines. However, the recent introduction of Therapeutic Biologics into veterinary medicine highlights the role of novel vaccine types licensed for the treatment, rather than prevention, of disease (especially cancer) in dogs and cats.

The list of Vaccine Types (below) corresponds with categories of vaccines recognized by the U.S. Department of Health & Human Services, but it has been modified to correspond with the terminology used throughout this version of the AAHA Canine Vaccination Guidelines. Examples include vaccines licensed for both dogs and cats.


Attenuated vaccines

Vaccine Type

Attenuated Vaccine

Alternative & Common Names

Modified-Live (virus);
Avirulent-live (bacteria)


Developed to induce an immune-response (humoral and cell-mediated) that mimics natural infection but without the disease-producing ability.

Attenuated vaccines are highly immunogenic and are capable of inducing a sustained, protective immune response with one dose (in the absence of maternally derived antibody), and today are regarded as very safe.

With current manufacturing technology, reversion of attenuated vaccine to a virulent, disease-producing state is exceptionally low to non-existent.

All vaccines licensed for oral or intranasal administration are attenuated. Inactivated (killed) vaccines will not immunize if administered onto a mucosal surface.

LIMITATIONS: Must be stored and handled properly, with strict attention to temperature, even in the lyophilized (free-dried) state. Following re-constitution, the vaccine dose should be administered promptly (within 1 hr) or discarded.


Most canine distemper virus vaccines.

All canine parvovirus and adenovirus-2 vaccines.

Inactivated vaccines

Vaccine Type

Inactivated Vaccine

Alternative & Common Names



These are highly stable preparations of whole-cell virus or bacteria incapable of replicating following administration. For this reason, inactivated vaccines are generally considered very safe.

With little exception (e.g., rabies vaccine) 2 initial doses of an inactivated vaccine, administered 2 to 4 wk apart, are required to immunize. Annual revaccination is usually recommended.

Although debated, inactivated vaccines may be more likely to be associated with acute adverse reactions following vaccination than other vaccine types. Small breed dogs receiving multiple doses of an inactivated vaccine at the same appointment may be at increased risk for an acute reaction. Sensitization to excipient proteins, adjuvant, as well as the immunizing antigen, may contribute to hypersensitivity reactions.

LIMITATIONS: Inactivated vaccines are generally less immunogenic and tend not to have an extended duration of immunity (memory) compared to attenuated vaccines utilizing the same organism. Inactivated vaccines often contain an adjuvant intended to incite local inflammation and enhance the immune response to the antigen. Post-vaccinal reactions associated with inactivated vaccines include injection-site pain and granuloma formation, as well as angioedema.


All canine rabies vaccines.

All whole-cell bacterins:

  • Leptospirosis (2- and 4-serovar) vaccines.
  • Some Borrelia burgdorferi (canine Lyme disease) vaccines.

Parenteral Bordetella bronchiseptica vaccine.

All canine influenza vaccines.

Some Feline Leukemia Vaccines.

Recombinant vaccines

Vaccine Type

Recombinant Vaccine

  • Virus-Vectored
  • Subunit
  • Chimeric

Alternative & Common Names

Genetically-engineered vaccine

DNA vaccine


Recombinant. Rather than inoculate a whole, attenuated, or inactivated virus or bacteria to induce immunity, selected portions of pathogen DNA (or RNA) may be isolated and removed from the disease-producing microbe. The isolated genetic material is subsequently inserted (recombined) with the DNA (or RNA) of a non-pathogenic organism (vector). Following inoculation, the immunizing antigen is expressed by the recombined DNA (or RNA), then is subsequently processed by antigen presenting cells and lymphocytes to induce an immune response.

Subunit. DNA may also be recombined with plasmid DNA and inserted into bacteria where a pure form of antigen (only) is expressed, subsequently isolated, and prepared as vaccine. Subunit recombinant vaccines do not contain constituent proteins from the pathogenic microbe.

Chimera. Unique, immunizing antigens may be constructed by combining multiple nucleic acids to produce a polyvalent antigen (e.g., OspC).



Recombinant Canine Distemper Virus vaccine (canarypox virus-vectored).

Recombinant Feline Rabies vaccine canarypox virus-vectored vaccine expressing glycoprotein G.

Recombinant (subunit) plasmid-expressed OspA for canine Lyme disease.

Recombinant-chimeric (subunit) canine Lyme disease expressing OspA and polyvalent OspC.

Toxoid vaccines

Vaccine Type

Toxoid Vaccines

Alternative & Common Names

“Detoxified” toxin


Toxoid vaccines are made from selected toxins (proteins) that have been sufficiently attenuated (rendered harmless) yet are able to induce a humoral (antibody) immune response.

Toxoid vaccines tend not to have a duration of immunity comparable to attenuated viral vaccines; therefore, multiple sequential initial doses may be required to protect (especially among very large and small breed dogs). Revaccination (booster) may be required multiple times in a single year depending on individual patient risk factors.



Crotalus atrox toxoid (Western Diamond rattlesnake) vaccine.

Therapeutic biologics

Vaccine Type

Therapeutic Biologics

Alternative & Common Names

Immunotherapeutic biologics (sometimes referred to as “therapeutic vaccines”)


“Therapeutic Biologics” are not conventional vaccines, although they do work through a variety of immunological mechanisms intended to support the treatment, not prevention, of specific non-infectious medical conditions, particularly cancer. Currently, therapeutic biologics fall into one of 4 sub-categories:

  • non-replicating recombinant antigens
  • monoclonal antibodies
  • synthetic peptides
  • nucleic acid-mediated

Autologous vaccines, on the other hand, are listed as therapeutic biologics but entail producing a novel, patient-unique vaccine developed from the patient’s own (tumor) tissue.


Canine oral melanoma vaccine (non-replicating recombinant antigen).

Canine atopic dermatitis immunotherapeutic (monoclonal antibody).

These guidelines are supported by a generous educational grant from
Boehringer Ingelheim USA Inc., Merck Animal Health, and Zoetis.