Morbilliviruses affect many mammalian taxa and vaccination is a routine prevention strategy for domestic animals and has been used successfully in wildlife. Canine distemper virus (CDV) and phocine distemper virus (PDV) are morbilliviruses that have caused dieoffs of tens of thousands of phocids. Exposure to CDV or PDV has not yet been detected in Hawaiian monk seals (HMS). Risk factors for HMS include out-of-habitat pinnipeds that carry morbillivirus into Hawaiian waters and interactions between HMS and infected feral or domestic dogs, which are increasingly common as human and seal populations in the main Hawaiian Islands increase. The 1,100 remaining HMS are distributed widely across the Hawaiian archipelago, complicating detection and outbreak response. Hence, introduction of morbillivirus into this immunologically naïve population would threaten the survival of this critically endangered species. Immunization trials of captive seals with a commercial canine distemper recombinant vaccine have documented production of CDV antibody without adverse effects. An implementation strategy has been developed for emergency vaccination of wild HMS in the event that exposure or disease is detected. Efforts to model the timeline and trajectory of an outbreak and the effect of vaccination schemes on disease spread are underway and will inform the strategic approach to an emergency vaccination response. Prophylactic vaccination of free-ranging HMS during directed efforts, during routine handling (e.g., tagging), combined with emergency outbreak response preparedness, is the most effective approach to protecting this critically endangered species. While designed with morbillivirus outbreak prevention in mind, this overall strategy can be easily adapted to prevention of other disease threats, including West Nile Virus.