Chlamydia trachomatis infection in urogenital tract, if untreated, can cause severe complications. Due to lack of obvious symptoms, many C. trachomatis-infected individuals are undiagnosed and untreated. Thus, there is an urgent need for an effective anti-C. trachomatis vaccine. Currently, no licensed C. trachomatis vaccine is available, mainly due to lack of knowledge on protective antigens in C. trachomatis. The failure of human trachoma vaccine trials using formalin-fixed whole C.