Understanding Risk for Vaccine Adverse Effects in Dogs

Jarod M. Hanson, DVM, PhD, DACVPM, DABT, University of Maryland

ArticleLast Updated November 20233 min read
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In the Literature

Moore GE, Morrison J, Saito EK, Spofford N, Yang M. Breed, smaller weight, and multiple injections are associated with increased adverse event reports within three days following canine vaccine administration. J Am Vet Med Assoc. 2023:1-7. doi:10.2460/javma.23.03.0181

The Research …

Adverse effects (AEs) of vaccines are a significant concern with emerging trends in vaccine hesitancy and avoidance. Fear of AEs is often anecdotally noted as a reason clients seek new clinicians and limit visits to the clinic. Vaccine hesitancy can impact mental and physical health of veterinary staff.1

Although AEs are assumed to have declined over time, this study provides a data-driven assessment of AEs in dogs. The study included 31,197 AEs in >4.6 million dogs during >16 million clinic visits and identified an AE rate of 19.4/10,000 visits (0.19%). This is lower than the rate found in a previous study2; however, these studies are not directly comparable due to differences in vaccine suppliers, vaccine composition, and other factors. Both studies found AE rates increased with inverse body weight, female sex, history of neuter, younger age, and increasing number of vaccines administered per visit. French bulldogs and dachshunds had the highest AE rates by breed in the current study. A separate literature review found 5 studies that showed consistent, although often weak, evidence that reduced body size correlates with enhanced risk for vaccine-associated AEs.3

AE risk was higher (adjusted odds ratio, >1.3) for rabies and canine distemper virus/canine adenovirus-2/canine parainfluenza virus/canine parvovirus vaccines and lower (adjusted odds ratio, ≤1.01) for Bordetella and canine influenza vaccines. Historically, rabies vaccines have higher levels of protein components, possibly contributing to higher overall AE rates.

… The Takeaways

Key pearls to put into practice:

  • Vaccines prevent and/or reduce the severity of infectious diseases and minimize potential for zoonotic diseases (eg, rabies). Risk for AEs should be balanced against risk for and impact of disease on patients and humans, including veterinary staff members. 

  • Although most AEs are mild to moderate, limiting the number of vaccinations per visit and time period in high-risk dogs may help decrease risk for AEs. Reducing the dose of vaccines has minimal to no supporting efficacy data, is not approved by the US Department of Agriculture for canine vaccines, and creates an assumption of liability by the clinician. 

  • Patient-specific risks, possible presentation (eg, clinical signs, timing) of AEs, and a treatment plan should be discussed with the client before vaccines are administered. To help reduce AE risk in high-risk patients, the number of individual vaccines given per visit can be limited, with additional visits to complete the course at least 2 weeks apart, increasing concern for pet owner compliance. In addition, mucosal/intranasal vaccines can be substituted for parenterally administered vaccines when possible, and high-risk patients can be premedicated with diphenhydramine or glucocorticoids. 

  • Reporting AEs to the manufacturer and US Department of Agriculture is critical to improve products and identify problems (see Suggested Reading).