Chlamydia vaccine shows promising results in early-stage trial

A Chlamydia vaccine showed promising results in an early-stage clinical trial conducted by researchers in the U.K. and Denmark.

The early phase of the research found the experimental vaccine to be safe. The study was conducted from 2020-22 with individuals split between women and men, none of whom had chlamydia. The researchers examined and tested various dosages of the vaccine, they reported Thursday in The Lancet Infectious Diseases.

Participants got the vaccine or a placebo during the four-month period of testing. 

Researchers noted that of 154 participants screened, 65 were randomly assigned and 60 finished the trial.

Chlamydia is a common sexually transmitted infection that can affect both men and women. The disease can permanently damage women’s reproductive system and make pregnancies difficult or sometimes impossible, according to the Centers for Disease Control and Prevention (CDC). 

No vaccine is currently available to protect against the disease. More than 1.6 million cases were reported in the U.S. in 2022, according to the CDC. 

During the trial, participants also received the vaccine through eye drops, apart from getting the shot in the arm. A Phase 2 trial will look at the effectiveness of the shot.

The next phase still has to answer questions, especially with the research being in its infancy. 

“Does it confer the ability to hold off infection with chlamydia?” Dr. Hilary Reno, a professor of medicine at Washington University in St. Louis, told NBC News. 

“If you do have an infection, does it mean you’re more likely to have an asymptomatic infection?” said Reno, who is also a medical director of the St. Louis County Sexual Health Clinic.

“We don’t know that, and that’s what the next phase of studies would be,” she added.