1. A method comprising: administering a first composition to a subject by an intranasal route, wherein the first composition comprises a vector comprising a polynucleotide encoding a fusion protein, wherein the fusion protein comprises a YscF protein domain, a mature F1 protein domain, and a LcrV protein domain; and administering a second composition to the subject by an intramuscular route, wherein the second composition comprises the fusion protein, wherein the fusion protein is isolated, and wherein the intramuscular administration is after the intranasal administration.

11. A method comprising: administering a composition to a subject by an intranasal route, wherein the composition comprises a vector comprising a polynucleotide encoding a fusion protein, wherein the fusion protein comprises a YscF protein domain, a mature F1 protein domain, and a LcrV protein domain; and administering a second administration of the composition to the subject by an intranasal route.

12. The method of claim 11 wherein the fusion protein comprises at least one linker, wherein the linker is present between two of the domains.

13. The method of claim 11 wherein the fusion protein comprises a His-tag.

14. The method of claim 11 wherein the vector is a replication defective adenovirus vector.

15. The method of claim 14 wherein the defective adenovirus vector is type-5 (Ad5).

16. The method of claim 11 wherein the fusion protein comprises the YscF protein, the mature F1 protein, and the LcrV protein.

17. The method of claim 11 wherein the subject is a human.

18. The method of claim 11 wherein the administering confers immunity to plague caused by Yersinia pestis.

19. The method of claim 18 wherein the plague is pneumonic plague or bubonic plague.