Image by CDC

Chlamydia is one of the most common sexually transmitted infections in the world, with doctors reporting 131 million new cases every year — but that number could drop dramatically thanks to a promising new chlamydia vaccine called CTH522.

CTH522 is the first chlamydia vaccine to ever reach a phase 1 clinical trial, the stage at which researchers test a medication or treatment in humans to ensure that it's safe.

On Monday, the international team of researchers behind the vaccine published the results of that trial in The Lancet Infectious Diseases journal — and not only does the vaccine appear safe, but it also provoked an immune response in all 30 study participants who received it, with each person's body producing antibodies that could defend against the infection.

"Of course, the research is still in its early days, but we're very happy," researcher Frank Follmann told NBC News. "We found a robust response."

Although chlamydia is already curable with antibiotics, nearly 75 percent of people who contract the STI never see any symptoms.

That means they can go years without treating the infection, perhaps unknowingly spreading it to other people — and that can be particularly dangerous for women, who can experience serious complications from a chlamydia infection, ranging from pelvic inflammatory disease to infertility.

A vaccine would be an ideal way to address the stealthy infection, as it could prevent contraction in the first place. However, the researchers will need to conduct additional trials to find out whether CTH522's immune response is effective at warding off chlamydia.

If it is, Toni Darville, chief of pediatric infectious disease at the University of North Carolina Children's Research Institute, who was not involved with the study, is hopeful that CTH522 could become a regular part of preventative healthcare.

"My hope would be to combine it with the HPV vaccine and deliver it in the same manner, at the same time," she told NBC. "The HPV vaccine prevents cancer. This vaccine would prevent infertility."