The present invention relates to means and methods to protect against disease caused by bacteria belonging to the genus Chlamydia. In particular, the present invention relates to isolated B- and T-cell epitopes derived from the major outer membrane protein of Chlamydia psittaci which can be used against an infection with a species of the genus Chlamydia. More in particular, the invention provides a vaccine which can be used against chlamydiosis caused by Chlamydia psittaci in birds and man. In addition, the invention relates to a diagnostic method to diagnose the latter infections.
