Using Multiple Outcomes of Sexual Behavior to Provide Insights Into Chlamydia Transmission and the Effectiveness of Prevention Interventions in Adolescents

• Published in: Sexually transmitted diseases Vol. 44; no. 10; p. 619
• Main Authors: Enns, Eva Andrea, Kao, Szu-Yu, Kozhimannil, Katy Backes, Kahn, Judith, Farris, Jill, Kulasingam, Shalini L
• Format: Journal Article
• Language: English
• Published: United States 01.10.2017
• Subjects: Adolescent; Adolescent Behavior; Chlamydia - physiology; Chlamydia Infections - microbiology; Chlamydia Infections - prevention & control; Chlamydia Infections - transmission; Computer Simulation; Condoms - statistics & numerical data; Female; Humans; Incidence; Male; Minnesota - epidemiology; Models, Theoretical; Pregnancy; Prevalence; Sexual Behavior; Sexually Transmitted Diseases - microbiology; Sexually Transmitted Diseases - prevention & control; Sexually Transmitted Diseases - transmission; Unsafe Sex; Young Adult
• ISSN: 1537-4521
• DOI: 10.1097/OLQ.0000000000000653

Mathematical models are important tools for assessing prevention and management strategies for sexually transmitted infections. These models are usually developed for a single infection and require calibration to observed epidemiological trends in the infection of interest. Incorporating other outcomes of sexual behavior into the model, such as pregnancy, may better inform the calibration process. We developed a mathematical model of chlamydia transmission and pregnancy in Minnesota adolescents aged 15 to 19 years. We calibrated the model to statewide rates of reported chlamydia cases alone (chlamydia calibration) and in combination with pregnancy rates (dual calibration). We evaluated the impact of calibrating to different outcomes of sexual behavior on estimated input parameter values, predicted epidemiological outcomes, and predicted impact of chlamydia prevention interventions. The two calibration scenarios produced different estimates of the probability of condom use, the probability of chlamydia transmission per sex act, the proportion of asymptomatic infections, and the screening rate among men. These differences resulted in the dual calibration scenario predicting lower prevalence and incidence of chlamydia compared with calibrating to chlamydia cases alone. When evaluating the impact of a 10% increase in condom use, the dual calibration scenario predicted fewer infections averted over 5 years compared with chlamydia calibration alone [111 (6.8%) vs 158 (8.5%)]. While pregnancy and chlamydia in adolescents are often considered separately, both are outcomes of unprotected sexual activity. Incorporating both as calibration targets in a model of chlamydia transmission resulted in different parameter estimates, potentially impacting the intervention effectiveness predicted by the model.