Canine distemper virus (CDV) is a highly contagious and often fatal disease that presents a major challenge for animal shelters, even those implementing recommended intake vaccination protocols. Despite widespread vaccination on intake, CDV outbreaks persist in Arizona shelters, raising concerns about vaccine efficacy, herd immunity, and unidentified risk factors for infection. This study aimed to identify factors associated with PCR-confirmed CDV infection and poor serologic response to CDV vaccination in a shelter population.