Vaccines – Adverse Events within Three Days JAVMA 10/1/05

  • The quotes in red below are from the attached scientific report covering adverse events within 3 days of vaccination in dogs over the course of 2 years. Reports of dogs having vaccinal adverse reactions within the same time frame were not included if heartworm medication had been administered along with the vaccines. This study did not include adverse reactions such as development of fibrosarcomas and/or other conditions which take longer than 3 days to develop.

    Moore, George E. et als., Adverse events diagnosed within three days of Vaccine Administration in Dogs, Journal of the American Veterinary Medical Association, Vol 227, No. 7, October 1, 2005

    Animals?1,226,159 dogs vaccinated at 360 veterinary hospitals.

    Results?4,678 adverse events (38.2/10,000 dogs vaccinated) were associated with administration of 3,439,576 doses of vaccine to 1,226,159 dogs. 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.

    Conclusions and Clinical Relevance?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.

    Records for dogs that received both an injectable heartworm preventive and a vaccine during the same office visit were not included in analyses.

    Population?In the 2-year study period, 4,531,837 vaccine doses were administered to 1,537,534 dogs at 360 veterinary hospitals.

    Among breeds with 5,000 or more dogs vaccinated, Dachshund, Pug, Boston Terrier, Miniature Pinscher, and Chihuahua breeds had the highest rates of VAAEs with 121.7, 93.0, 83.8, 76.4, and 76.1 adverse events/10,000 dogs vaccinated, respectively (Table 1). The VAAE rate for mixed-breed dogs was in the bottom quintile of all rates.

    The VAAE rates decreased significantly as body weight increased (P for trend < 0.001; Figure 1). For all vaccines or for rabies vaccine alone, the VAAE rate for 10.1- to 45.0-kg (22.2- to 99.0-lb) dogs was approximately half the rate for dogs that weighed 0 to 10.0 kg (0 to 22.0 lb; P < 0.001; Figure 2). For rabies vaccine administered alone, VAAE rates/10,000 dogs that weighed 0 to 10.0 kg, 10.1 to 45.0 kg, and > 45 kg were 32.1 (222/69,178), 15.3 (69/45,088), and 0.0 (0/1,966), respectively.

    The risk of a VAAE significantly increased as the number of vaccines administered per office visit increased (P for trend < 0.001).

    In all dogs, each additional vaccine administered per office visit increased the rate of a VAAE by 24.2%; the rate increase was significantly (P <0.001) greater in dogs that weighed 0 to 10.0 kg, compared with dogs that weighed 0.1 to 45.0 kg (27.3% vs 11.5%, respectively; Figure 4). The 3 dogs with recorded deaths each had received ≥ 4 vaccines at their last office visit.

    The lowest rate was observed with parenteral administration of Bordetella vaccine (15.4/10,000; 82 VAAEs/53,238 doses), and the highest rate was observed with Borrelia (Lyme disease) vaccine (43.7/10,000; 132 VAAEs/30,201 doses).

    The risk of a VAAE in this study population was inversely related to a dog?s weight.

    Factors known to cause vaccine reactions include the primary vaccine agent or antigen, adjuvants, preservatives, stabilizers, and residues from tissue cultures used in vaccine production.

    The overall formulation of various vaccine components (eg, antigen, adjuvants, and diluent) is proprietary information that was unavailable for analysis in our study; thus, the variation in VAAE rates among single-antigen vaccines
    may not be solely attributable to the primary vaccine antigen.

    … because of genetic heterogeneity, the relatively low VAAE rate observed in mixed-breed dogs suggests that laboratory safety trials that use such dogs may underestimate the VAAE rates that would occur in purebred dogs. This is important because purebred dogs comprise at least two thirds of the US dog population.

    The risk of allergic reaction has been reported to increase after the third or fourth injection of a vaccine (ie, a booster response).

    Neutering appeared to increase risk of a VAAE more than sex. Females mount stronger immune responses after vaccination or infection than males because of a dimorphic enhancing effect of estrogens and a protective effect of androgens.

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