Vaccine-based prophylaxis has greatly helped to keep distemper disease under control. Notwithstanding, the incidence of canine distemper virus (CDV)–related disease in canine populations throughout the world seems to have increased in the past decades, and several episodes of CDV disease in vaccinated animals have been reported, with nation-wide proportions in some cases. Increasing surveillance should be pivotal to identify new CDV variants and to understand the dynamics of CDV epidemiology. In addition, it is important to evaluate whether the efficacy of the vaccine against these new strains may somehow be affected.