A Purdue University vet school study (by Moore et al), published in 2005 in the AVMA Journal and widely-cited elsewhere (see AAHA Guidelines p. 22), tracked vaccine reactions occurring within 72 hours of vaccination for 1.2 million dogs vaccinated at 360 veterinary hospitals. It showed that small breed dogs receiving multiple vaccines per office visit were at greatest risk of a vaccine reaction. The report recommends: these factors should be considered in risk assessment and risk communication with clients regarding vaccination.
“The VAAE [reaction] 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.” (Find the article: JAVMA, Vol 227, No. 7, October 1, 2005).
Note too: In the WSASA Guidelines Q & A: Are certain vaccines or combinations of vaccines more likely to cause adverse reactions than others? Yes. Although the development of an adverse reaction is often dependent on the genetics of the animal (e.g. small breed dogs or families of dogs), certain vaccines have a higher likelihood of producing adverse reactions, especially reactions caused by Type I hypersensitivity. For example, bacterins (killed bacterial vaccines), such as Leptospira, Bordetella, Borrelia (Lyme) and Chlamydophila (Chlamydia) are more likely to cause these adverse reactions than MLV viral vaccines.
Breeds Most at Risk Listed in Order (for breeds with more than 5000 dogs studied)
Jack Russell Terrier
American Eskimo Dog
American Cocker Spaniel
American Pit Bull Terrier
Australian Cattle Dog
German Shepherd Dog