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.