HM02 - Temporal Associations Between Vaccination and Onset of Immune-mediated Hemolytic Anemia or Thrombocytopenia in Dogs.

Abstract:

Background: Vaccination has been implicated in development of human immune-mediated diseases, but previous studies investigating similar associations in dogs yielded conflicting results for immune-mediated hemolytic anemia (IMHA) and thrombocytopenia (ITP). Hypothesis/

Objectives: To investigate temporal relationships between onset of IMHA or ITP and vaccination in client-owned dogs. We hypothesized that the proportion of dogs vaccinated within 1 month would be higher in the IMHA/ITP groups compared to controls. Animals: Client-owned dogs with non-associative IMHA (n=270) and ITP (130) presented to 3 referral hospitals from 2010 through 2022, alongside age-matched dogs with non-immune mediated disease (n=1080 for IMHA, 520 for ITP) presented contemporaneously to the same institutions.

Methods: A multicenter retrospective case control study was conducted. Fisher’s exact test was used to compare the proportion of dogs with IMHA or ITP that were vaccinated in the month before disease onset compared to control dogs.

Results: The proportion of dogs vaccinated within 1 month of diagnosis was significantly higher in the IMHA group (33/270, 12.2%) compared with matched controls (68/1080, 6.3%, p=0.002). There was no difference in the proportion of dogs with ITP that were vaccinated in the month before diagnosis compared to controls (16/130, 12.3% versus 43/520, 8.3%, p=0.17). Dogs with IMHA vaccinated in the month before diagnosis were significantly older than those vaccinated at other times, but there were no differences in clinicopathological variables. Conclusions and Clinical importance: Our findings support a possible temporal association between vaccination and onset of IMHA in dogs, but confirm lack of association for ITP.