Chlamydia Vaccine May Be on the Horizon

A vaccine yielded an immune response against Chlamydia trachomatis in an early trial, raising hopes it could tackle the rising rates of the sexually transmitted infection (STI).

Chlamydia trachomatis is the most common bacterial STI in the United States, with nearly 1.7 million cases reported in 2022. The rates of chlamydia have been on the rise since the beginning of the COVID-19 pandemic, including among senior citizens.

The infection can be effectively treated with antibiotics; however, many cases are asymptomatic, allowing the infection to spread further. If left untreated, the infection can lead to serious complications such as infertility and irreversible vision loss.

A phase-1 clinical trial, the findings of which were published in the Lancet Infectious Diseases, included 65 participants aged 18 to 45 without chlamydia.

They were randomized into getting different doses of the vaccine supplemented with mucosal ocular pull — a vaccine antigen administered via eye drops — or a placebo on three separate days over a period of more than three months.

All vaccinated participants who received the vaccine and those who also received a mucosal ocular pull generated neutralizing antibodies in the blood and eyes.

The vaccine was also found to be safe and well-tolerated, as the majority of adverse events were mild to moderate.

“We envision a future chlamydia vaccine that is able to protect against both urogenital infections and possibly ocular infections and are in the process of developing such a vaccine, now that this trial has demonstrated how such a vaccine is to be administered in order to be both safe and immunogenic,” says the study’s author Jes Dietrich, senior scientist at the Statens Serum Institut in Denmark.

Currently, there is no vaccine against chlamydia available, and prevention includes the use of barrier birth control like condoms and regular screening. U.S. health officials now recommend taking an antibiotic doxycycline within 72 hours of condomless sex to reduce the risk of developing common STIs.

Further trials are necessary to determine the effectiveness of the investigational vaccine. If eventually approved for use, researchers say the vaccine could significantly change the landscape for chlamydia.