STDs in Adolescents and Young Adults

Background

Incidence and prevalence estimates suggest that young people aged 15–24 years acquire half of all new STDs1 and that one in four sexually-active adolescent females has an STD, such as chlamydia or human papillomavirus (HPV).2 Compared with older adults, sexually-active adolescents aged 15–19 years and young adults aged 20–24 years are at higher risk of acquiring STDs for a combination of behavioral, biological, and cultural reasons. For some STDs, such as chlamydia, adolescent females may have increased susceptibility to infection because of increased cervical ectopy. Cervical ectopy refers to columnar cells, which are typically found within the cervical canal, located on the outer surface of the cervix. Although this is a normal finding in adolescent and young adult females, these cells are more susceptible to infection. The higher prevalence of STDs among adolescents may also reflect multiple barriers to accessing quality STD prevention and management services, including inability to pay, lack of transportation, long waiting times, conflict between clinic hours and work and school schedules, embarrassment attached to seeking STD services, method of specimen collection, and concerns about confidentiality (e.g., Explanation of Benefits for services received mailed to parents or guardians).3

Traditionally, intervention efforts have targeted individual level factors associated with STD risk which do not address higher-level factors (e.g., peer norms and media influences) that may also influence behaviors.4 Interventions for at-risk adolescents and young adults that address underlying aspects of the social and cultural conditions affecting sexual risk-taking behaviors are needed, as are strategies designed to improve the underlying social conditions themselves.5,6 In addition, in designing STD programs, consideration should be given to the needs of adolescent and young adult populations including extended clinic hours, optimizing privacy in waiting rooms, and urine based specimen collection.3

Chlamydia

In 2018, there were 1,087,277 reported cases of chlamydial infection among persons aged 15–24 years, representing 61.8% of all reported chlamydia cases. Among those aged 15–19 years, the rate of reported cases of chlamydia increased 1.8% during 2017–2018 (from 2,072.3 to 2,110.6 cases per 100,000 population) (Table 10). Among those aged 20–24 years, the rate increased 1.6% during 2017–2018 (from 2,853.7 to 2,899.2 cases per 100,000 population) (Table 10).

Among females aged 15–24 years, the population targeted for chlamydia screening, the overall rate of reported cases of chlamydia in 2018 was 3,693.6 cases per 100,000 females (Table 12A). While this was only a 1.0% rate increase from 2017 (3,655.5 cases per 100,000 females), it was an 11.8% increase from 2014 (3,305.2 cases per 100,000 females). Among males aged 15–24 years, the overall rate of reported cases of chlamydia (1,382.0 cases per 100,000 males) increased 3.5% from 2017 (1,335.6 cases per 100,000 males) and 30.9% from 2014 (1,055.4 cases per 100,000 males) (Table 12B). Rates varied by state for both males and females. The majority of states having the highest reported case rates were in the South (Figure K and Figure L).

15–19 Year Old Females — In 2018, the rate of reported chlamydia cases among females aged 15–19 years was 3,306.8 cases per 100,000 females, a 1.3% increase from the 2017 rate of 3,264.8 cases per 100,000 females (Figures 5 and 6, Table 10). Increases in rates of reported cases of chlamydia during 2017–2018 were largest among 18–year old women (2.9%) (Table 12A). During 2014–2018, the overall rate of reported cases for females aged 15–19 years increased 12.1% (Table 10).

20–24 Year Old Females — In 2018, women aged 20–24 years had the highest rate of reported chlamydia cases (4,064.6 cases per 100,000 females) compared with any other age group for either sex (Figures 5 and 6, Table 10). The rate of reported chlamydia cases among women aged 20–24 years remained relatively stable during 2017–2018 (0.8% increase); however, within this age group, females aged 20 years had an increase of 3.3% (Table 12A). During 2014–2018, the rate of reported chlamydia cases in 20–24 year old females increased 11.9% (Table 10).

15–19 Year Old Males — In 2018, the rate of reported chlamydia cases among males aged 15–19 years (959.0 cases per 100,000 males) increased 3.7% from 2017. During 2014–2018, the rate of reported chlamydia cases for males aged 15–19 years increased 32.8% (Figures 5 and 7, Table 10).

20–24 Year Old Males — In 2018, as in previous years, men aged 20–24 years had the highest rate of reported chlamydia cases among all males (1,784.5 cases per 100,000 males). The rate for men in this age group increased 3.3% during 2017–2018 and 31.1% during 2014–2018 (Figures 5 and 7, Table 10).

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Gonorrhea

During 2017–2018, the rate of reported gonorrhea cases decreased 1.3% for persons aged 15–19 years and increased 1.2% for persons aged 20–24 years (Table 21). In 2018, among females aged 15–24 years, the rate was 627.0 cases per 100,000 females (Table 23A). This was only a 0.1% increase from 2017 (626.3 cases per 100,000 females) but a 29.7% increase from 2014 (483.4 cases per 100,000 females). Among males aged 15–24 years, the rate was 525.6 cases per 100,000 males in 2018. This was only a 0.4% increase from 2017 (523.5 cases per 100,000 males) but a 46.7% increase from 2014 (358.3 cases per 100,000 males). For both females and males, rates varied by state. The majority of states with the highest reported case rates were in the South (Figures M and N).

15–19 Year Old Females — In 2018, females aged 15–19 years had the second highest rate of reported gonorrhea cases (548.1 cases per 100,000 females) compared with other age groups among females (Figures 19 and 20, Table 21). During 2017–2018, the rate of reported gonorrhea cases for females in this age group decreased 1.7% but increased 27.0% during 2014–2018 (Table 21).

20–24 Year Old Females — In 2018, women aged 20–24 years had the highest rate of reported gonorrhea cases (702.6 cases per 100,000 females) compared with other age groups among females (Figures 19 and 20, Table 21). During 2017–2018, the rate of reported gonorrhea for women in this age group only increased 1.5% but increased 32.3% during 2014–2018 (Table 21).

15–19 Year Old Males — In 2018, the rate of reported gonorrhea cases among males aged 15–19 years was 320.5 cases per 100,000 males (Figures 19 and 20, Table 21). During 2017–2018, the rate of reported gonorrhea cases for males in this age group decreased 0.9% but increased 44.1% during 2014–2018 (Table 21).

20–24 Year Old Males — In 2018, as in previous years, men aged 20–24 years had the highest rate of reported gonorrhea cases (720.9 cases per 100,000 males) compared with any other age group for either sex (Figures 19 and 20, Table 21). During 2017–2018, the rate of reported gonorrhea for men in this age group only increased 1.0% but increased 49.2% during 2014–2018 (Table 21).

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Primary and Secondary Syphilis

In 2018, the rate of reported primary and secondary (P&S) syphilis among females aged 15–24 years was 7.2 cases per 100,000 females, a 28.6% increase from 2017 (5.6 cases per 100,000 females) and a 100.0% increase from 2014 (3.6 cases per 100,000 females). Among males aged 15–24 years in 2018, the rate was 28.2 cases per 100,000 males, a 7.2% increase from 2017 (26.3 cases per 100,000 males) and a 44.6% increase from 2014 (19.5 cases per 100,000 males). During 2017–2018, the rate of reported P&S syphilis cases increased 14.9% among persons aged 15–19 years and 10.3% among persons aged 20–24 years (Table 34).

15–19 Year Old Females — In 2018, the rate of reported P&S syphilis cases among females aged 15–19 years increased 34.4% from 2017 (from 3.2 to 4.3 cases per 100,000 females) and 72.0% from 2014 (2.5 cases per 100,000 females) (Figures 42 and 43, Table 34).

20–24 Year Old Females — In 2018, women aged 20–24 years had the highest rate of P&S syphilis (10.0 cases per 100,000 females) compared with other age groups among females (Figures 42 and 43, Table 34). The P&S syphilis rate among women in this age group has increased each year since 2011 and has increased 122% (4.5 cases per 100,000 females) (Figure 43, Table 34). During 2017–2018, the rate increased 26.6%.

15–19 Year Old Males — In 2018, the rate of reported P&S syphilis cases among males aged 15–19 years was 10.9 cases per 100,000 males (Figures 42 and 44, Table 34). The P&S syphilis rate among males in this age group has increased each year since 2011, with an increase of 53.5% from 2014 (7.1 cases per 100,000 males) and 7.9% from 2017 (10.1 cases per 100,000 males) (Figure 44, Table 34).

20–24 Year Old Males — In 2018, the rate of reported P&S syphilis among males aged 20–24 years was 44.6 cases per 100,000 males (Figures 42 and 44, Table 34). The P&S syphilis rate among men in this age group has increased each year since 2006, with a 44.3% increase from 2014 (30.9 cases per 100,000 males) and 7.0% from 2017 (41.7 cases per 100,000 males) (Figure 44, Table 34).

Other STDs

Human papillomavirus

Human papillomavirus (HPV) is a common sexually transmitted infection in the United States.1 Starting in 2006, HPV vaccines have been recommended for routine use in United States females aged 11–12 years, with catch-up vaccination through age 26.7,8  Since late 2011, routine use of the HPV vaccine has been recommended for males aged 11–12 years, with catch-up vaccination through age 21;8-10 this age limit was recently extended to 26 years.11 Vaccination through age 26 has been recommended for gay, bisexual, and other men who have sex with men (MSM) and persons who are immunocompromised (including those infected with HIV).8 In October 2018, the Food and Drug Administration (FDA) extended licensing approval of the vaccine for women and men aged 27–45 years,12 and in June 2019, the CDC’s Advisory Committee on Immunization Practices (ACIP) recommended that unvaccinated adults aged 27–45 years discuss receiving the HPV vaccine with their health care providers.11 For more information on HPV vaccination, see Other STDs.

A recent meta-analysis that included data from over 60 million individuals from 14 high-income countries, including the United States, showed a substantial impact of HPV vaccination on: genital HPV infections among adolescent girls and young women; high-grade cervical lesions among young women; and anogenital warts among adolescent boys and girls, and among young men and women.13 Cervicovaginal prevalence of any quadrivalent HPV vaccine type has been estimated for civilian, non-institutionalized females aged 14–34 years using data from the National Health and Nutrition Examination Survey (NHANES; see Section A2.4 in the Appendix).14 Prevalence decreased significantly from 2003–2006 (the pre-vaccine era) to 2011–2014 in specimens from females aged 14–19 years and 20–24 years, the age groups most likely to benefit from HPV vaccination.

Health-care claims data from adolescents and adults with employer-provided private health insurance in the United States were used to examine the population effectiveness of HPV vaccination on two clinical sequelae of HPV infection: high-grade histologically-detected cervical intraepithelial neoplasia grades 2 and 3 (CIN2+),15 and anogenital warts.16 Prevalence of CIN2+ and of anogenital warts decreased significantly during 2007–2014 among females aged 15–19 and 20–24 years (Figures 51 and 52A); prevalence of anogenital warts also decreased significantly during 2009–2014 among women aged 25–29 years (Figure 52A). These declines provide ecologic evidence of population effectiveness of HPV vaccination in females. Anogenital wart prevalence also decreased significantly during 2009–2014 among men aged 20–24 years (Figure 52B); these declines among young men are consistent with herd protection from vaccination among females.

For more information on HPV infections, see Other STDs.

Herpes simplex virus

Herpes simplex virus (HSV) is among the most prevalent of sexually transmitted infections.1,17 Most genital HSV infections in the United States are caused by HSV type 2 (HSV-2), while HSV type 1 (HSV-1) infections are typically orolabial and acquired during childhood.18,19 NHANES data have shown that among adolescents aged 14–19 years, HSV-1 seroprevalence has significantly decreased by almost 23%, from 39.0% during 1999–2004 to 30.1% during 2005–2010, indicating declining orolabial infection in this age group.19 HSV-2 seroprevalence in this age group was much lower in both time periods.19

Other studies have found that genital HSV-1 infections are increasing among young adults.20-22 This has been attributed, in part, to the decline in orolabial HSV-1 infections, because those who lack HSV-1 antibodies at sexual debut are more susceptible to genital HSV-1 infection.19,23 Increasingly common oral sex behavior among adolescents and young adults also has been suggested as a contributing factor.19,24

NHANES data have shown that among pregnant women with three or fewer lifetime sex partners, seronegativity for both HSV-1 and HSV-2 increased from 1999–2006 to 2007–2014,25 raising the possibility that pregnant women with fewer sex partners may have increased risk of acquiring genital HSV during pregnancy and vertically transmitting HSV to their neonates.

For more information on genital HSV infections, see Other STDs. For information on neonatal HSV infections, see Special Focus Profiles, STDs in Women and Infants.

National Job Training Program

The National Job Training Program (NJTP) is an educational program for socioeconomically disadvantaged youth aged 16–24 years and is administered at more than 100 sites throughout the country. The NJTP screens participants for chlamydia and gonorrhea within two days of entry to the program. All of NJTP’s chlamydia screening tests and the majority of gonorrhea screening tests are conducted by a single national contract laboratory (Center for Disease Detection, LLC, San Antonio, Texas).

To increase the stability of the 2018 estimates, chlamydia or gonorrhea prevalence data are presented when valid test results for 100 or more students per year are available for the population subgroup and state. Additional information about NJTP can be found in Section A2.1 in the Appendix.

Among females aged 16–24 years entering the program in 2018 in 41 states and the District of Columbia, the median state-specific chlamydia prevalence was 12.5% (range: 5.7% to 19.3%) (Figure O). Among males aged 16–24 years entering the program in 2018 in all 50 states, the District of Columbia, and Puerto Rico, the median state-specific chlamydia prevalence was 6.6% (range: 1.0% to 13.3%) (Figure P).

Among females aged 16–24 years entering the program in 41 states and the District of Columbia, the median state-specific gonorrhea prevalence in 2018 was 2.2% (range: 0.4% to 7.6%) (Figure Q). Among males aged 16–24 years entering the program in 46 states, the District of Columbia, and Puerto Rico, the median state-specific gonorrhea prevalence in 2018 was 0.7% (range: 0.0% to 4.8%) (Figure R).

Figure O - Among females aged 16–24 years entering the National Job Training Program in 2018 in 41 states and the District of Columbia, the median state-specific chlamydia prevalence was 12.5% (range: 5.7% to 19.3%).

Figure O - Among males aged 16–24 years entering the National Job Training Program in 2018 in all 50 states, the District of Columbia, and Puerto Rico, the median state-specific chlamydia prevalence was 6.6% (range: 1.0% to 13.3%).

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See text for description.

Summary

The rate of reported cases of chlamydia, gonorrhea, and P&S syphilis increased for both sexes in 15–24 year olds during 2017–2018. For chlamydia, rates of reported cases are consistently highest among females aged 15–24 years, likely reflecting targeted screening of young women; however, rates of reported gonorrhea cases are consistently highest among males aged 15–24 years. These high rates among males aged 15–24 years likely reflect a combination of recent increased screening efforts in young men, including extra-genital screening, as well as increased incidence. Although rates of reported chlamydia and gonorrhea increased only marginally among both sexes during 2017–2018, the increases observed before 2017 were much more striking. The rate of reported chlamydia in females and males aged 15–24 years increased 1.0% and 3.5%, respectively, during 2017–2018; however, increases of 11.8% and 30.9% were noted during 2014–2018 for females and males aged 15–24 years, respectively. Similarly, the rate of reported gonorrhea in females and males aged 15–24 years increased 0.1% and 0.4%, respectively, during 2017–2018; however, increases of 29.7% and 46.7% were noted during 2014–2018 for females and males aged 15–24 years, respectively. Whether these smaller increases in the past year compared to the past five years indicate a slowing to the increasing trend of rates of chlamydia and gonorrhea cannot be assessed with current data, and will take further years of case surveillance to determine. Similar to gonorrhea, rates of reported cases of P&S syphilis have been consistently higher among adolescent and young adult males compared to females; however, the largest increase in P&S syphilis has been observed in females aged 15–24 years. Rates of reported P&S syphilis cases increased 28.6% and 7.2% during 2017–2018 and increased 100.0% and 44.6% during 2014–2018 for females and males aged 15–24 years, respectively.

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