Background:The most recent estimates of the number of prevalent and incident sexually transmitted infections (STIs) in the United States were for 2008. We provide updated estimates for 2018 using new methods. Methods:We estimated the total number of prevalent and incident infections in the United States for 8 STIs: chlamydia, gonorrhea, trichomoniasis, syphilis, genital herpes, human papillomavirus, sexually transmitted hepatitis B, and sexually transmitted HIV. Updated per-capita prevalence and incidence estimates for each STI were multiplied by the 2018 full resident population estimates to calculate the number of prevalent and incident infections. STI-specific estimates were combined to generate estimates of the total number of prevalent and incident STIs overall, and by sex and age group. Primary estimates are represented by medians, and uncertainty intervals are represented by the 25th (Q1) and 75th (Q3) percentiles of the empirical frequency distributions of prevalence and incidence for each STI.Results: In 2018, there were an estimated 67.6 (Q1, 66.6; Q3, 68.7) million prevalent and 26.2 (Q1, 24.0; Q3, 28.7) million incident STIs in the United States. Chlamydia, trichomoniasis, genital herpes, and human papillomavirus comprised 97.6% of all prevalent and 93.1% of all incident STIs. Persons aged 15 to 24 years comprised 18.6% (12.6 million) of all prevalent infections; however, they comprised 45.5% (11.9 million) of all incident infections. Conclusions:The burden of STIs in the United States is high. Almost half of incident STIs occurred in persons aged 15 to 24 years in 2018. Focusing on this population should be considered essential for national STI prevention efforts.

Background Human papillomavirus (HPV) vaccine was recommended in 2006 for routine vaccination of US females aged 11–12 years. Most vaccine used through 2014 was quadrivalent vaccine (4vHPV), which prevents HPV-6, -11, -16, and -18 infection. To evaluate vaccine impact, we measured HPV prevalence in the National Health and Nutrition Examination Survey (NHANES). Methods We analyzed HPV DNA types detected in self-collected cervicovaginal specimens and demographic, sexual behavior, and self-reported vaccination data from females 14–34 years old. We estimated HPV prevalence in the prevaccine (2003–2006) and vaccine eras (2007–2010 and 2011–2014). Results Among 14- to 19-year-olds, 4vHPV-type prevalence decreased from 11.5% (95% confidence interval [CI], 9.1%–14.4%) in 2003–2006 to 3.3% (95% CI, 1.9%–5.8%) in 2011–2014, when ≥1-dose coverage was 55%. Among 20- to 24-year-olds, prevalence decreased from 18.5% (95% CI, 14.9%–22.8%) in 2003–2006 to 7.2% (95% CI, 4.7%–11.1%) in 2011–2014, when ≥1-dose coverage was 43%. Compared to 2003–2006, 4vHPV prevalence in sexually active 14- to 24-year-olds in 2011–2014 decreased 89% among those vaccinated and 34% among those unvaccinated. Vaccine effectiveness was 83%. Conclusions Within 8 years of vaccine introduction, 4vHPV-type prevalence decreased 71% among 14- to 19-year-olds and 61% among 20- to 24-year-olds. Estimated vaccine effectiveness was high. The decrease in 4vHPV-type prevalence among unvaccinated females suggests herd protection.

Background Highly effective human papillomavirus (HPV) vaccines are used in many national programs in 3- or 2-dose schedules. We examined HPV vaccine effectiveness against HPV prevalence by number of doses. Methods We collected residual liquid-based cytology samples from US women aged 20–29 years who were screened for cervical cancer. Women continuously enrolled from 2006 through the specimen collection date were analyzed. Specimens were tested using the Linear Array assay. We analyzed prevalence of quadrivalent HPV vaccine (4vHPV) types (HPV 6,11,16,18) and other HPV-type categories and determined prevalence ratios (PRs) and 95% confidence intervals (CIs) for 1, 2, and 3 compared with no vaccine doses. Results Among 4269 women, 1052 (24.6%) were unvaccinated, 2610 (61.1%) received 3 doses, 304 (7.1%) received 2 doses, and 303 (7.1%) received 1 dose. The 4vHPV-type prevalence was 7.4% among unvaccinated women compared with 1.7%, 1.0%, and 1.0% among 1-, 2-, and 3-dose recipients. Among women vaccinated at ≤18 years, adjusted PRs for 1, 2, and 3 doses were 0.06 (95% CI, 0.01–0.42), 0.05 (95% CI, 0.01–0.39), and 0.06 (95% CI, 0.04–0.12). Conclusions Among women who received their first dose at age ≤18, estimated HPV vaccine effectiveness was high regardless of number of doses.