STI Synopsis


The world’s most commonly reported bacterial STI, chlamydia is a major cause of infertility.

Chlamydia can be cured with antibiotics, but because most people experience no symptoms and tests are often unavailable or unaffordable, it often goes undiagnosed and untreated, leading to onward transmission as well as high rates of reinfection.


Despite decades of research and hundreds of studies, a successful chlamydia vaccine has not yet been identified. However, promising new tools have emerged in recent years, including technology to genetically manipulate chlamydia. Modeling studies also suggest that a chlamydia vaccine could be cost-effective.

Statens Serum Institut and Imperial College London published results of a small phase I safety and immunogenicity study in 2019 and recently completed a larger phase I trial.

Next steps for vaccine development includes:

Assess Public Health Value

  • Obtain better data on the burden of chlamydia-associated infertility, and other adverse consequences, in different settings globally
  • Continue to model the theoretical impact of chlamydia vaccines

Facilitate Research and Development

  • Continue to advance basic science, translational research and clinical development of chlamydia vaccines

Optimize Global Benefits and Access

  • Identify preferred product characteristics to drive development of suitable vaccines for populations who would benefit the most
  • Lay the groundwork for fast, targeted rollout of vaccines so they have the greatest impact


Chlamydia testing includes both culture and nonculture methods. Historically, culture tests were considered the gold standard to detect chlamydia, but NAAT tests, a nonculture method, are now considered the gold standard after demonstrating high sensitivity and specificity.

Additionally, NAATs can often conduct tens to hundreds of tests at a time. Many newer diagnostics have combined chlamydia and gonorrhea tests to detect both at once.

131 million new cases each year

Even when asymptomatic, chlamydia can damage the reproductive system, potentially causing infertility in women

Chlamydia is curable but frequently undiagnosed due to lack of symptoms and limited testing, causing ongoing transmission and reinfection.

Learn More

Luis M. de la Maza, Toni L Darville & Sukumar Pal (2021): Chlamydia trachomatis vaccines for genital infections: where are we and how far is there to go?, Expert Review of Vaccines, DOI: 10.1080/14760584.2021.1899817

Phillips S, Quigley BL, Timms P. Seventy Years of Chlamydia Vaccine Research – Limitations of the Past and Directions for the Future. Front Microbiol. 2019;10:70. doi: 10.3389/fmicb.2019.00070.