Methods for stimulating immune responses in a bovine animal susceptible to infection by Leptospira hardjo-bovis are disclosed. In the methods, a composition of inactivated L. hardjo-bovis and an adjuvant is administered to the animal within about 4 weeks of birth. The immune responses stimulated in the animal prevent or shorten the duration of a subsequent L. hard jo-bovis infection. The immune response is effective for at least a year.
