(TIME) — There could be a chlamydia vaccine in the coming years, a promising new study suggests.
The first human trial of a chlamydia vaccine shows that it is safe and triggers an immune response, a promising step toward an STI vaccine.
U.S. sexually transmitted illness diagnoses have reached new highs for the past four years in a row, and chlamydia is responsible for the bulk of those infections: 1.7 million cases were diagnosed in 2017 alone, according to the U.S. Centers for Disease Control and Prevention, compared to about 550,000 cases of gonorrhea, 40,000 cases of HIV and 30,000 cases of syphilis. Globally, the problem is even more widespread: about 127 million cases were diagnosed in 2016, according to the World Health Organization. But despite its prevalence, chlamydia can be difficult to diagnose because many people do not show symptoms. That means people may unknowingly pass it on to partners or delay treatment for themselves. But just because it doesn’t always cause obvious symptoms doesn’t mean chlamydia isn’t harmful; over time, the infection raises the risk of infertility and chronic pelvic pain, especially for women, and can make people more susceptible to other infections, including HIV.