Objective: To determine incidence rates (IRs) and potential risk factors for owner-reported adverse events (AEs) following vaccination of dogs that did or did not receive a Leptospira vaccine.
Design: Observational, retrospective cohort study.
Animals: 130,557 dogs.
Procedures: Electronic records of mobile veterinary clinics from June 2012 to March 2013 were searched to identify dogs that received ≥ 1 vaccine in a given visit. Signalment data, vaccinations received, medications administered, and owner-reported clinical signs consistent with AEs that developed ≤ 5 days after vaccination were recorded. Associations between potential risk factors and owner-reported AEs were evaluated by logistic regression analysis.
Results: The IR/10,000 dogs for owner-reported postvaccination AEs was 26.3 (95% CI, 23.6 to 29.2), whereas that for dogs that received a Leptospira vaccine alone or with other vaccines was 53.0 (95% CI, 42.8 to 64.9). Significant factors for increasing or decreasing risk of AEs were as follows: receiving a Leptospira vaccine (adjusted OR, 2.13), age at vaccination 1 to < 7 or ≥ 7 years (vs a referent of < 6 months; adjusted OR, 0.54 and 0.44, respectively), and weight 13.6 to < 22.7 kg (30 to < 50 lb) and 22.7 to < 45.5 kg (50 to 100 lb [vs a referent of < 4.5 kg {10 lb}]; adjusted OR, 0.48 and 0.55, respectively). Hypersensitivity reactions were rare (IR, 6.5/10,000 dogs), and IRs for these events did not differ significantly between dogs vaccinated with or without a Leptospira component.
Conclusions and clinical relevance: The overall IR for owner-reported postvaccination AEs was low. Results suggested vaccination against Leptospira (an organism that can cause fatal disease) is safe in the majority of cases, slightly increasing the risk of owner-reported AEs but not associated with a significant increase in hypersensitivity reactions, compared with other vaccinations administered.