Within two years of becoming sexually active, about 50 percent of teenage girls in U.S. cities acquire one of three common sexually transmitted infections (STIs)—chlamydia, gonorrhea or trichomoniasis, according to a report published in the Archives of Pediatrics & Adolescent Medicine and reported by HealthDay News.

The study of 381 girls, ages 14 to 17, found that 75 percent had repeat infections in two years and 92 percent within four years. Researchers also found that often young girls did not get screened for STIs until several years after becoming sexually active.

“Four to six months after the treatment of the previous infection, a quarter of the women were re-infected with the same organism,” said Wanzhu Tu, PhD, associate professor of medicine at the Indiana University School of Medicine and a researcher at the Regenstrief Institute.

Researchers recommended sexually active teen girls start STI screenings within a year after they first have intercourse. They also suggested those who already had an STI get retested every three to four months.  

“This is important because many clinicians are reluctant to address sexual activity with younger teens and may miss important prevention opportunities,” said the study’s lead author J. Dennis Fortenberry, MD, a professor of pediatrics at the Indiana University School of Medicine.

Learn more about STIs among African Americans here.