The purposes of this study were: 1) to investigate the distribution of IgA-protease genotypes in a collection of consecutive clinical respiratory tract H. influenzae isolates from patients with respiratory tract infections as well as in a more diverse collection of encapsulated and invasive isolates, and 2) to assess the association between IgA-protease subtype and type of clinical infection. This evidence concerns the gene CD79A and Respiratory tract infection.