Understanding canine vaccines: What is ‘core’ and ‘non-core’?

Hopefully, the updated AAHA guidelines will help with re-thinking conversations about what defines “core” for each of our patients

Cost-conscious or vaccine-hesitant clients may decline vaccines the veterinary team does not specifically classify as core or ‘required’ for their pet. However, this is where a change in both perspective and narrative with clients might be needed.The American Animal Hospital Association (AAHA) recently released its 2022 AAHA Canine Vaccination Guidelines.1 This resource is incredibly comprehensive (almost any question you might have related to vaccination is addressed!), contains resources for veterinary team members and pet owners, and assists with preventive care. Perhaps the most important question raised in the updated guidelines is: “Should we be re-thinking what we consider ‘core vaccines’ for individual patients?” Spoiler alert: the answer is yes.

‘Core’ and ‘non-core’ vaccines

Traditional core vaccines are those recommended for all pets, regardless of lifestyle. These vaccines protect against diseases that are easily transmissible, serious, and/or fatal. The following are core vaccines AAHA recommends for every dog (unless there is a medical reason for exemption):

  • Canine distemper virus (CDV)
  • Canine adenovirus type 2 (CAV-2)
  • Canine parvovirus type 2 (CPV-2)
  • Rabies virus

Other vaccines (i.e. “non-core”) are sometimes considered “optional.” Here, cost-conscious or vaccine-hesitant clients may decline vaccines the veterinary team does not specifically classify as core or “required” for their pet. However, this is where a change in both perspective and narrative with clients might be needed.

These “non-core” vaccines may be considered “core” for certain dogs, and the AAHA similarly states the vaccines below may be essential based on dog lifestyle and risk:

  • Leptospira
  • Lyme
  • Bordetella (+/- parainfluenza)
  • Canine influenza
  • Western diamondback rattlesnake toxoid

For each of the vaccines listed, it is imperative veterinarians assess the individual dog’s risk factors and perhaps re-evaluate how they communicate specific dog vaccine needs to pet owners. For example, if Leptospirosis vaccines are presented as optional (“non-core”), clients may decline them despite it being a risk for a given region. Education of our clients and team in assessing individual dog risk factors, might be followed by phrasing such as, “This is an essential vaccine for your pet due to risk,” and thus achieve our (and our client’s) goals of protecting the pet.

Risk assessment

An easy way to implement this vaccine risk assessment practice would be to have veterinary technicians/nurses ask specific lifestyle questions at the start of the appointment by using a pre-printed checklist (e.g. Does your dog go to doggie daycare/ hiking/swimming?)

Additionally, AAHA has a Vaccine Lifestyle Calculator2 into which you enter the age of the pet and click checkboxes about the pet’s lifestyle to help generate vaccine recommendations. This calculator is super-efficient (takes less than a minute) and can be done in the exam room. An added benefit of this resource might be clients seeing the recommendations from a third-party source, which can help assuage concerns that vaccine recommendations are revenue- versus pet-health driven.

Resources that determine infectious disease risk in your area can also aid in client communication. An example is the Pet Disease Alerts website, established by the Companion Animal Parasite Council (CAPC),3 that provides prevalence maps (e.g. leptospirosis, canine influenza) as well as “Pet Parasite Forecasts” for tick-borne diseases (e.g. Lyme, anaplasmosis), which are freely available online and updated every 30 days.

‘Non-core’ vaccine considerations

Despite being referred to as “non-core,” many of these vaccines may be indicated for dogs, based on lifestyle and risk. Let’s briefly dive deeper into these vaccine considerations.

  • Leptospirosis. The AAHA strongly suggests we consider Lepto vaccination for most dogs in North America. This echoes the 2010 American College of Veterinary Internal Medicine (ACVIM) Consensus Guidelines on Leptospirosis which state the vaccine may be considered core in geographic locations where infections occur.4

Leptospirosis is endemic in much of the continent, represents a zoonotic risk, and, while infections are often associated with exposure to water, have been documented in arid regions like Arizona. Risk factors include dogs spending any time outdoors (including urban, suburban, and rural environments); exposure to rodents, and boarding in kennels or attending doggy daycares.

Vaccine-hesitant pet owners may have concerns about increased risk of adverse events (AEs) with Leptospira vaccines. Reviewing data from studies on post-Lepto vaccination AEs can help educate our clients and ease concerns. In these studies, AEs that occurred were mild, there was no difference in severe hypersensitivity-type events in dogs receiving Lepto vaccines versus others,5 and no increased allergenicity of combination Leptospira vaccines.6

In general, AEs are more likely in smaller dogs5,6 and have been shown to increase with the number of vaccines administered per office visit.This does not mean we should avoid vaccinating small breed dogs at risk of Lepto. Rather, it means we might have a discussion of risk with the client, consider modification of the dog’s vaccination protocol to limit the number of vaccinations per visit, and work together to mitigate risk of AEs.

  • Lyme disease – Borrelia burgdorferi or Lyme disease is transmitted via Ixodes ticks – I. scapularis for much of the U.S. and Canada, and I. pacificus along the Pacific coast. Per the AAHA, dogs that live in or travel to regions where these tick vectors are present should be vaccinated against Lyme disease. An important note here is querying pet-owners on upcoming travel, as both initial vaccines should be completed two to four weeks prior to travel to Lyme- endemic areas.

Here again, vaccine hesitancy may arise from a perceived increased risk of Lyme vaccine associated AEs. However, in a 2020 study of 620 dogs, mild AEs were rare, the most common being injection site edema (3.8 percent) and no serious AEs were noted.7

What should be the discussion in the exam room regarding Lyme vaccines? Assess risk in your geographical area, and discuss this and other factors (i.e. Is the patient at increased risk for AEs due to size or number of vaccines being given that day?), to determine the ideal protocol for that patient.

Wherever you (and the client) may land on the “to vax or not to vax” question, consider stringent monthly tick control “core” for dogs in these regions. • Bordetella bronchiseptica (Bb) (+/- CPIV, CAV-2). AAHA guidelines state dogs at risk for Bordetella (namely dogs that commingle with other dogs at dog shows/parks, daycare, grooming facilities, kennels, etc.) are also at risk for CPIV and CAV-2. These dogs should be vaccinated for all three pathogens, and the intranasal (IN) route is preferred for Bb to take advantage of enhanced respiratory immune response with IN versus oral delivery. Annual boosters are recommended. However, it may be advantageous for patients at high risk of Bb and CPIV to receive IN combination vaccines more frequently, for example, before boarding.

  • Canine influenza virus (CIV). Canine influenza serotypes H3N8 and H3N2 have been documented in North America. Infections tend to occur as multi-centric outbreaks; therefore, routine use of influenza vaccines is not currently recommended by the AAHA. Rather a patient’s individual risk should be determined based on disease status in your region.

Staying alert to upticks in canine infectious respiratory disease (CIRD) in your area, attempting to obtain an etiologic diagnosis of CIRD outbreaks using molecular diagnostics (such as PCR-based respiratory panels), and consulting online resources tracking flu outbreaks can assist with defining dog vaccine needs.

Resources to understand specific regional (or travel-related) risks and address concerns of vaccine availability include the “Worms & Germs Blog”8 mapping of the H3N2 outbreak that has been occurring in the U.S. since fall 2022. When vaccinating dogs for CIV, AAHA recommends use of bivalent vaccines.

  • Western diamondback rattlesnake (Crotalus atrox) venom toxoid. This region-specific vaccine may be a consideration for dogs within the southwestern U.S. where this rattlesnake resides. However, the AAHA notes there are no published data documenting efficacy of this toxoid in dogs, and it is unknown if this product provides cross-protection against other snake envenomation.

Hopefully the updated AAHA guidelines, and this review, will help with re-thinking concepts and conversations about what defines “core” for each one of our patients. Ultimately, it is provision of evidence- and expert-based education of (and shared decision-making with) pet owners regarding vaccines, and other aspects of preventive care (e.g. GI parasite surveillance, nutrition), that will achieve optimal (and individualized) pet care.

Danielle Davignon MS, DVM, DACVIM (SAIM), has worked in mixed-animal general practice and specialty clinical practice. Dr. Davignon has taught in veterinary technology programs and currently provides lectures on internal medicine topics to new DVM graduates in clinical practice mentorship programs. Davignon works as an Internal Medicine Consultant for Antech Diagnostics.

Michelle Evason, BSc, DVM, DACVIM (SAIM), MRCVS, serves as global director, Veterinary Clinical Education for Antech (MARS). Dr. Evason has worked in general practice, academia, specialty clinical practice, and in the animal health industry. She has published on numerous infectious diseases, antimicrobial stewardship, nutrition, spectrum of care, veterinary- and pet-owner education related topics.


  1. 2022 AAHA Canine Vaccination Guidelines, American Animal Hospital Association (AAHA), Accessed March 2023: https://www.aaha.org/aaha-guidelines/2022-aaha-canine-vaccination-guidelines/home
  2. Vaccine Lifestyle Calculator, American Animal Hospital Association (AAHA), Accessed March 2023: https://www.aaha.org/aaha-guidelines/2022-aaha-canine-vaccination-guidelines/vaccine-lifestyle-calculator
  3. Pet Disease Alerts, Companion Animal Parasite Council (CAPC), Accessed March 2023: https://petdiseasealerts.org
  4. Sykes JE, Hartmann K, Lunn KF, et al. 2010 ACVIM small animal consensus statement on leptospirosis: diagnosis, epidemiology, treatment, and prevention. J Vet Intern Med. 2011 Jan-Feb;25(1):1-13. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3040842/
  5. Yao PJ, Stephenson N, Foley JE, et al. Incidence rates and risk factors for owner-reported adverse events following vaccination of dogs that did or did not receive a Leptospira vaccine. J Am Vet Med Assoc 2015; 247:1139–45. https://pubmed.ncbi.nlm.nih.gov/26517617
  6. Moore GE, Guptill LF, Ward MP, et al. Adverse events diagnosed within three days of vaccine administration in dogs. J Am Vet Med Assoc 2005 Oct 1;227(7):1102-8. https://pubmed.ncbi.nlm.nih.gov/16220670
  7. Marconi RT, Honsberger N, Teresa Winkler M, et al. Field safety study of VANGUARD crLyme: A vaccine for the prevention of Lyme disease in dogs. Vaccine X. 2020 Oct 22;6:100080. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7733143
  8. “Canine Influenza Mapping” Worms & Germs Blog, University of Guelph Centre for Public Health & Zoonoses, Accessed March 2023: https://www.wormsandgermsblog.com/2022/12/articles/animals/dogs/canine-influenza-mapping

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