FDA Grants Fast Track Designation to Sanofi’s mRNA Chlamydia Vaccine

The FDA has granted Fast Track designation to Sanofi’s mRNA vaccine candidate for chlamydia prevention. The vaccine was designed to protect against both primary infection and reinfection by Chlamydia trachomatis, a leading cause of infertility and pregnancy complications. A Phase I/II study will evaluate its immunogenicity and safety as part of the Translational Science Hub, a collaboration with several Australian research institutions.^1,2

“Millions of people currently live with undiagnosed chlamydia, including asymptomatic infection that can also cause severe long-term health effects if left untreated,” said Jean-François Toussaint, global head of vaccines R&D, Sanofi, in a press release. “Antibiotics to treat chlamydia have not been successful in controlling rising infection rates. With our program we aim to make chlamydia a preventable disease through vaccination.”

The randomized, placebo-controlled, multi-arm, dose-finding study will enroll approximately 1,560 patients aged 18 to 29 years. The trial will include three sentinel cohorts to evaluate the safety of different dosing levels, as well as a main cohort. After the final intervention, all patients will continue follow-up for one year, with the study expected to conclude by January 3, 2028.²

According to Sanofi, there were approximately 129 million global cases of chlamydia in patients between 15 and 49 years of age in 2020, with a higher number of cases in adolescents and young adults.1 According to the World Health Organization, the global prevalence for the aforementioned age group was 4% in women and 2.5% in men.³

The Centers for Disease Control and Prevention reported 1,648,568 cases of chlamydia in the United States in 2023. Between 2022 and 2023, the rate of infection in men increased by 1.3%, while the rate in women decreased by 1.7%. Adolescents and young adults aged 15 to 24 years accounted for 55.8% of all cases.⁴

Chlamydia, the most common bacterial STI in the United States, affects around 1.5 million individuals annually. In addition to adolescents and young adults, men who have sex with men and Black, non-Hispanic populations are also disproportionately affected.⁵

References

1. Press Release: Chlamydia vaccine candidate granted fast track designation by the US FDA. Sanofi. March 26, 2025. Accessed March 27, 2025. https://www.sanofi.com/en/media-room/press-releases/2025/2025-03-26-06-00-00-3049326

2. Phase 1/​2 Study of Chlamydia Trachomatis mRNA Vaccine in Adults Aged 18 to 29 Years. Clinicaltrials.gov. Accessed March 27, 2025. https://clinicaltrials.gov/study/NCT06891417?cond=Chlamydia&term=vaccine&rank=2

3. Chlamydia. WHO. November 21, 2024. Accessed March 27, 2025. https://www.who.int/news-room/fact-sheets/detail/chlamydia#:~:text=Scope%20of%20the%20problem,more%20common%20in%20young%20people.

4. National Overview of STIs in 2023. CDC. Accessed March 27, 2025. https://www.cdc.gov/sti-statistics/annual/summary.html#:~:text=In%202023%2C%20a%20total%20of%201%2C648%2C568%20cases%20of%20Chlamydia%20trachomatis,initial%20shelter%20in%20place%20orders.

5. Chlamydia. Cleveland Clinic. Accessed March 27, 2025. https://my.clevelandclinic.org/health/diseases/4023-chlamydia