Chlamydia Vaccine Research

Development of a vaccine against Chlamydia is an international priority, but the complex lifestyle of the pathogen makes vaccine development challenging. SSI has developed a unique vaccine strategy to combat this challenging infection.

Why do we need a vaccine?

Chlamydia is the most common sexually transmitted bacterial disease in the world. Chlamydia is primarily a disease in young adults after their sexual debut with more than 131 million people infected each year. Infections often go undiagnosed, as they remain asymptomatic in 75% of women and 50% of men. Many countries focus on case management through screening and targeted treatment in risk populations, a strategy that, until now, has not reduced incidence rates. Untreated infections in women increase the risk of developing severe complications, leading to pelvic inflammatory disease (PID) and long-term sequelae such as infertility and ectopic pregnancy. Thus, there is a great need to develop a vaccine against Chlamydia.

Chlamydia trachomatis - a pathogen with a complex lifestyle

Chlamydia is caused by an infection with the bacteria C. trachomatis. The bacteria is very much like a virus, meaning it relies totally on its host to survive and replicate. C. trachomatis has two developmental forms: a small (0.3 microns) non-replicating infectious form which, after attachment, is internalized into the host cell and instantly reorganized into a metabolically active and replicating form of almost triple the size. After completion of a replicative cycle, it reorganizes into the infectious form again and is released from the host cell. If the bacteria is not controlled by the immune system, it may ascend to infect the fallopian tubes and can cause major damage leading to pelvic inflammatory disease, scarring and occlusion.

Chlamydia vaccine research at the SSI

At SSI, our strategy is to develop a vaccine that targets the bacterium very early, i.e. immediately after it enters the genital tract. We envision a vaccine that elicits both cell-mediated and humoral immunity; a primary role of neutralizing antibodies to reduce initial infectious load and once the bacteria are intracellular, they will be targeted by a bactericidal cell-mediated immune response. We have completed an extensive discovery program in the search for vaccine candidates and are continuously studying the immunological mechanism underlying protection from both infection and disease. SSI's vaccine candidate (CTH522) has completed clinical phase Ia and Ib clinical testing Lancet Infect Disand Research Square.

Research projects


Title: Novel vaccine vectors to resist pathogen challenge

Objective: The objective of VacPath is to establish a much needed technological infrastructure in Europe along with educating and training young scientist by promoting the development of innovative, protective and safe vaccines for future clinical use. 

Funded by: European Union, Marie Sklodowska-Curie Innovative Training Networks, Horizon 2020 

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Partners: Statens Serum Institut (Denmark), University of Utrecht (NL), Heinrich-Heine University (Germany), University of Basel (Switzerland), University of Siena (Italy), Microbiotec SRL (Italy) and Abera Bioscience AB (Sweden)

Contact: Jes Dietrich,

 Pioneer Th17 T cells

Title: Pioneer The17 T cells facilitate recruitment of Th1 T cells into infected genital tract tissue

Objective: Understanding how to induce an early detection of the Chlamydia bacteria is a key issue in the Chlamydia research field (and for other genital infections), in the context of vaccine development. Although it is believed that early recruitment to the genital tract (GT) of T helper 1 (Th1) T cells is crucial, we will in this project test our hypothesis that it is in fact Th17 T cells that are first recruited to the GT, where they actively participate in combating the bacteria and also aid Th1 T cells in participating in a protective immune response. In addition, we will also develop and test new vaccine strategies and if resident immunity is required to combat the infection. 

Funded by: Independent Research Fund Denmark


Contact: Jes Dietrich,

Specific Th17/exTh17 T cell subsets

Title: Specific Th17/exTh17 T cell subsets mediate protective immunity in the genital tract against infection with Chlamydia trachomatis

Objective: The goal is to investigate Th17 T cells and their role in combatting an infection with Chlamydia trachomatis (C.t.). The optimal immune response against this infection is not fully resolved and, in particular, the role of th17 T cells is not known. However, we have recently obtained preliminary data that suggested Th17 T cells as key players in protecting the genital tract (GT) against infection and that they exist as several subsets. In this project, we will investigate this further, and we hope to deliver 1) the first conclusive evidence that Th17 T cells are protective against a C.t. bacterial infection, 2) the first characterization of all Th17/exTh17 T cell subsets and their interplay with a C.t. infection and 3) a vaccine strategy to favor protective Th17 T cell subsets.

Funded by: Independent Research Fund Denmark  


Contact: Jes Dietrich,

Frank Follmann


Frank Follmann, Director, MSc, PhD, Infektionsimmunologi
T. +45 32688296 @. View profile