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. A 1st generation vaccine candidate has completed clinical phase I trial.

Research projects



Title: Developing a Chlamydia Trachomatis Vaccine

Objective: The TracVac consortium works towards eliminating the global problem of blinding trachoma through the development of a vaccine. TracVac has two main objectives. The first main objective is to generate a vaccine that protects against the bacterial strains causing ocular Chlamydia trachomatis infections. The second objective is to develop an immunization protocol for optimal mucosal immunity. Read more at

Partners: TracVac is an European consortium consisting of 4 partners, Statens Serum Institut (DK), Imperial College (UK), London School og Hygiene & Tropical Medicine (UK) and The French Alternative Engergies and Atomic Energy, CEA (France)

Funded by: The European Union, Horizon 2020

EU logo  TracVac logo

Contact: Frank Follmann,


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 

EU logo

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

Contact:Frank Follmann,

Frank Follmann


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