Pertactin (PRN) is an outer membrane protein expressed by Bordetella pertussis, Bordetella parapertussis, and Bordetella bronchiseptica, which induces protective immunity to Bordetella infections. The immunodominant and immunoprotective epitopes of pertactin include two repeated regions, I and II. Comparison of these two repeated regions showed the pertactin of B. parapertussis is invariant, whereas the pertactin of B. pertussis varies mostly in region I and B. bronchiseptica varies in both the repeated regions I and II. Compositions containing pertactins and pertactin fragments containing variant sequences in these regions are useful as immunogenic compositions.