Provided herein are methods for using compositions that include a fusion protein having a YscF protein domain, a mature F1 protein domain, and a LcrV protein domain. In one embodiment the composition is used to confer immunity to plague, such as pneumonic plague, caused by Yersinia pestis. In one embodiment, the composition is administered to a mucosal surface, such as by an intranasal route. In one embodiment, the administration to a mucosal surface includes a vector that has a polynucleotide encoding a fusion protein, where the fusion protein includes a YscF protein domain, a mature F1 protein domain, and a LcrV protein domain. The administration is followed by a second administration by a different route, such as an intramuscular route. The second administration includes a fusion protein having the same three domains, and in one embodiment the fusion protein is the same one administered to a mucosal surface.