Impacts of changing sexual behavior on chlamydia and gonorrhea burden among US high school students, 2007-2017.

BACKGROUND Rates of adolescent sexual activity have long been declining in the United States. We sought to estimate the number of cases of gonorrhea and chlamydia averted over one decade associated with these declines, and associated costs saved. METHODS We analyzed data from the CDC's Youth Risk Behavior Survey of US high-school students from 2007-2017 and combined it with epidemiological estimates drawn from the literature to parameterize a dynamic population transmission model. We compared transmissions from observed behavioral trends to a counterfactual scenario that assumed sexual behaviors from 2007 remained constant over 10 years. We calculated outcomes by age and for three racial/ethnic groups (Hispanic, non-Hispanic Black, and non-Hispanic White adolescents) who vary on underlying burden and amount of behavioral change. RESULTS We estimated 1,118,483 cases of chlamydia and 214,762 cases of gonorrhea were averted (19.5% of burden across all ages). This yielded $474 million (2017 dollars) savings in medical costs over the decade. The largest number of averted cases (767,543) was among Black adolescents, but the largest proportion (28.7%) was among Hispanic adolescents. CONCLUSIONS Whatever its origins, changing sexual behavior among adolescents results in large estimated reductions in STI burden and medical costs relative to previous cohorts. Although diagnoses among adolescents have not declined at this rate, multiple explanations could make these apparently divergent trends consistent. Efforts to continue supporting effective sex education in and out of school along with STI screening for adolescents should reinforce these gains.