A bacterin including effective immunizing amounts of two non-crossprotective isolates of inactivated Borrelia burgdorferi, an adjuvant in an amount effective to enhance the immunogenicity of the inactivated Borrelia burgdorferi isolates and a suitable carrier is provided herein. The bacterin may also contain a third non-crossprotective isolate. A bacterin including effective immunizing amounts of an antigenic subunit derived from a first Borrelia burgdorferi isolate and a second, non-crossprotective Borrelia burgdorferi isolate, an adjuvant in an amount effective to enhance the immunogenicity of the antigenic subunits and a suitable carrier is also provided. The bacterin may also contain an effective immunizing amount of an antigenic subunit of a third Borrelia burgdorferi. Further provided is a bacterin which includes effective immunizing amounts of two non-crossprotective isolates of inactivated Borrelia burgdorferi and one or more antigenic subunits from the non-crossprotective isolates, an adjuvant in an amount effective to enhance the immunogenicity of the inactivated Borrelia burgdorferi and antigenic subunits and a suitable carrier. Methods of immunizing an animal against Borrelia burgdorferi infection which comprise administering to the animal a dose of a bacterin provided herein are also provided.
