The invention is in the field of outer membrane vesicles (OMV) and their uses. More particularly the present invention provides OMV obtained from a bacterium being an ompA mutant and/or a mutant in one or more components of the TolPal complex and presenting a heterologous antigen on its surface. The heterologous antigen is selected from the group consisting of Chlamydia trachomatis CT823, CT681, CT372, CT443, CT043, CT733, CT279, CT601 and CT153 for the treatment, prevention or diagnosis of Chlamydia infection.
