Inhalation of Yersinia pestis bacilli causes pneumonic plague, a rapidly progressing and exceptionally virulent disease. Extensively antibiotic-resistant Y. pestis strains exist and we currently lack a safe and effective pneumonic plague vaccine. These facts raise concern that Y. pestis may be exploited as a bioweapon. Here, I review the history and status of plague vaccine research and advocate that pneumonic plague vaccines should strive to prime both humoral and cellular immunity.