Abstract: An isolated and purified analog of Haemophilus influenzae Hin47 protein has a decreased protease activity which is less than about 10 % of that of natural Hin47 protein and preferably substantially the same immunogenic properties as natural Hin47 protein. An isolated an purified nucleic acid molecule encoding the Hin47 analog may be provided in a recombinant plasmid which may be introduced into a cell which is grown to produce the Hin47 analog. Immunogenic compositions comprising the Hin47 analog and the encoding nucleic acid may be formulated as vaccines for in vivo administration to a host, including a human, to confer protection against diseases caused by a bacterial pathogen, including Haemophilus species, such as Haemophilus influenzae, that produces Hin47 protein or a protein capable of inducing antibodies in the host specifically reactive with Hin47 protein. The Hin47 analog and the encoding nucleic acid also may be employed in diagnostic applications.