An Argument For Splitting Up Vaccines In Small Dogs

Risk Factors for Vaccine-associated Adverse Events (VAAEs) in Small Dogs


A study, namely ‘Adverse events diagnosed within three days of vaccine administration in dogs’ by GE Moore et al [2005]*, has indicated that a greater percentage of small dogs experience vaccine-associated adverse events (VAAEs). The conclusions and clinical relevance of the study stated the following: 

‘Young adult small-breed neutered dogs that received multiple vaccines per office visit were at greatest risk of a VAAE within 72 hours after vaccination. These factors should be considered in risk assessment and risk communication with clients regarding vaccination.’

Evidently then, injection of multiple vaccines at one time is likelier to produce vaccine-associated adverse events in small dogs.


The study indicated that the risk of a vaccine-associated adverse event (VAAE) was inversely related to a dog’s weight. Genetics of the animal, for example small breed dogs or families of dogs, can also play a role and components other than the primary antigen may contribute to adverse events as well. Still, low weight as a risk factor carries more weight, so to speak:

‘The VAAE rate decreased significantly as body weight increased. Risk was 27% to 38% greater for neutered versus sexually intact dogs and 35% to 64% greater for dogs approximately 1 to 3 years old versus 2 to 9 months old. The risk of a VAAE significantly increased as the number of vaccine doses administered per office visit increased; each additional vaccine significantly increased risk of an adverse event by 27% in dogs ≤ 10 kg (22 lb) and 12% in dogs > 10 kg.’


Splitting up vaccines, so a dog does not get more than one vaccine per visit, can be done. A veterinarian can split up and give vaccines on different days, for example, two weeks apart. It may not be convenient for the owner or fun for the dog, but if it reduces the risk of a vaccine-associated adverse event, it is worth it.


Even though vaccines are tested for efficacy and safety, no vaccine is completely effective or absolutely reaction free. However, it is also important to realize that evidence of vaccine-associated adverse events (VAAEs) does not mean vaccines are not safe; instead it shows a small risk of adverse events associated with certain dog factors or vaccines.

These findings are important as they should be considered in risk assessment and risk communication with veterinarians and dog owners prior to vaccination.

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