Vaccine-type Human Papillomavirus Prevalence Research Articles

Prevalence of Genital Human Papillomavirus by Age and Race/Ethnicity Among Males.

Genital and oral cancers are often caused by human papillomavirus (HPV) types that can be prevented through HPV vaccination. Since HPV is sexually transmitted, knowledge of penile prevalence of vaccine-type HPV among US males can help predict potential disparities in these cancers. This study examines penile HPV prevalence by age and race/ethnicity among males. This study was a secondary analysis of publicly available data from the National Health and Nutrition Examination Survey (NHANES). Using data from penile swab samples collected from males between 2013 and 2016, the prevalence of 4vHPV and 9vHPV vaccine types was examined across age groups and by race/ethnicity. Logistic regression models adjusting for demographics, sexual behavior, and circumcision were examined to determine whether associations remained after accounting for confounders. Among 2548 males evaluated, HPV infection prevalence differed by race/ethnicity, with Black males exhibiting a higher prevalence of HPV. Examination of 4vHPV type prevalence by age group showed that 18-26-year-old males had a lower prevalence than older age groups. After controlling for confounders, 4vHPV prevalence was only significantly elevated among 27-34-year-old males, those who were single, and males with ≥3 lifetime sex partners. In adjusted models, 9vHPV type prevalence remained elevated among Black males compared with White males. Variations in 9vHPV type prevalence between Black and White individuals indicate future disparities in HPV-related genital cancers may continue in the United States during the next decade. Revaccinating certain populations with the 9vHPV vaccine may be appropriate to help mitigate this.

Vaccine Effectiveness Against Prevalent Anal and Oral Human Papillomavirus Infection Among Men Who Have Sex With Men-United States, 2016-2018.

In the United States, human papillomavirus (HPV) vaccination has been recommended for young adult men who have sex with men (MSM) since 2011. The Vaccine Impact in Men study surveyed MSM and transgender women aged 18-26 years in 3 US cities during 2016-2018. Self-collected anal swab and oral rinse specimens were assessed for 37 types of HPV. We compared HPV prevalence among vaccinated and unvaccinated participants and determined adjusted prevalence ratios (aPR) and 95% confidence intervals (CI). Among 1767 participants, 704 (39.8%) self-reported receiving HPV vaccine. Median age at vaccination (18.7 years) was older than age at first sex (15.7 years). Quadrivalent vaccine-type HPV was detected in anal or oral specimens from 475 (26.9%) participants. Vaccine-type HPV prevalence was lower among vaccinated (22.9%) compared with unvaccinated (31.6%) participants; aPR for those who initiated vaccination at age ≤18 years was 0.41 (CI, 0.24-0.57) and at age >18 years was 0.82 (CI, 0.67-0.98). Vaccine effectiveness of at least 1 HPV vaccine dose at age ≤18 years or >18 years was 59% and 18%, respectively. Findings suggest real-world effectiveness of HPV vaccination among young adult MSM. This effect was stronger with younger age at vaccination.

Geographical disparities in human papillomavirus herd protection.

BackgroundHuman papillomavirus (HPV) vaccination has occurred unequally across the United States, potentially contributing to uneven vaccine‐type HPV prevalence between regions. We examined whether emerging vaccine‐related herd protection exhibits regional differences among unvaccinated girls and women.MethodsWe evaluated the prevalence of vaginal HPV among women 14‐59 years of age from 2003 to 2014 using repeated cross‐sectional data from the National Health and Nutrition Examination Survey (NHANES). Women who provided an adequate vaginal swab sample were included. Vaginal prevalence of vaccine‐type HPV (types 6, 11, 16, 18) were examined in four regions of the United States between 2003 and 2014. We examined vaccine‐type HPV prevalence in 2007‐2014 in each US census region among younger participants (14‐34 years old) stratified by vaccination status to determine whether one or both groups contributed to uneven HPV prevalence.ResultsA total of 12 175 participants 14‐59 years of age met inclusion criteria. Vaccine‐type HPV prevalence decreased in all regions. Vaccine‐type HPV varied by region only among unvaccinated 14‐34 year olds, with a higher prevalence in the Midwest (13.8%, 95% confidence interval (CI): 10.7‐17.0) and South (12.5%, 95% CI: 10.2‐14.8) compared to the Northeast (8.9%, 95% CI: 6.5‐11.2). No regional variation in vaccine‐type HPV prevalence was observed among vaccinated participants.ConclusionsHigher prevalence of vaccine‐type HPV among unvaccinated women in the South and Midwest may contribute to regional disparities in HPV‐related cancer incidence, as emerging herd immunity may not be as strong in those regions.

Decline in vaccine-type human papillomavirus prevalence in young men from a Midwest metropolitan area of the United States over the six years after vaccine introduction

PurposeThe aim of this study was to determine changes in human papillomavirus (HPV) prevalence among young men from a Midwest metropolitan area over the six years after vaccine introduction, including HPV prevalence in men overall, in vaccinated men to examine vaccine impact and in unvaccinated men to examine herd protection. An exploratory aim was to examine associations between number of vaccine doses and HPV prevalence. MethodsMen aged 14–26 years reporting male-female and/or male-male sexual contact were recruited from a primary care clinic, sexually transmitted disease clinic, and community setting during two waves of data collection: 2013–2014 (N = 400) and 2016–2017 (N = 347). Participants completed a questionnaire and were tested for penile, scrotal and anal HPV. Changes in prevalence of any (≥1 type) and vaccine-type HPV (HPV6, 11, 16, and/or 18) were examined using propensity score weighted logistic regression. Associations between number of doses and HPV infection were determined using chi-square tests and logistic regression. ResultsThe proportion of men with a history of ≥1 HPV vaccine doses increased from 23% to 44% (p < 0.001) from waves 1 to 2. After propensity score weighting, infection with ≥1 vaccine-type HPV significantly decreased among all men (29% to 20%; 31% decrease; odds ratio [OR] = 0.62, 95% confidence interval [CI] = 0.44–0.88) and unvaccinated men (32% to 21%; 36% decrease; OR = 0.56, 95%CI = 0.34–0.86); there was a non-significant decrease (21%) among vaccinated men. Associations between number of doses and HPV prevalence were not statistically significant. ConclusionsPrevalence of vaccine-type HPV decreased among all, vaccinated, and unvaccinated men six years after HPV vaccine recommendation, supporting vaccine impact and herd protection. Decreases in vaccine-type HPV in all men appear to be due to decreases in unvaccinated men, suggesting that the full impact of vaccination has yet to be realized. Continued monitoring and efforts to vaccinate men prior to sexual initiation are warranted.

Regional variations in human papillomavirus prevalence across time in NHANES (2003–2014)

IntroductionThe consequences of low human papillomavirus (HPV) vaccination in Census regions with higher incidence of cervical cancer may contribute to continued disparities. Our purpose was to evaluate regional variations in HPV prevalence across time. MethodsRepeated cross-sectional data from the National Health and Nutrition Examination Survey (NHANES), 2003–2014 were examined. Participants included females 14 to 34 years old who provided adequate vaginal samples for HPV DNA typing (N = 6387). Region of residence and HPV vaccination status associations with HPV prevalence were examined using chi-square and multivariable logistic regression. HPV types were grouped according to vaccine-type HPV (types 6, 11, 16, 18) and risk (high or low-risk). Time and vaccination status were included in subsequent models for post-licensure survey cycles (2007–2014) to assess their effects on observed associations. ResultsNo decreases in vaccine-type HPV prevalence were found between the prevaccine cycles (2003–2006) and early post-licensure cycles (2007–2010, p > 0.05). Vaccine-type HPV prevalence decreased in late post-licensure years (2011–2014) compared to prevaccine years (2003–2006, p = 0.001). The highest prevalence of vaccine-type HPV occurred in the South (8.6%) and Midwest (8.6%), followed by the West (4.8%), and the Northeast (3.5%) in late post-licensure years. Lower odds of vaccine-type HPV across time in post-licensure survey cycles were found to be attributable to time, and more strongly to HPV vaccination. ConclusionsThere were regional variations in vaccine-type HPV prevalence between prevaccine and post-licensure years. These decreases appeared to be at least partially attributable to HPV vaccination. Programs are needed to address geographical disparities in HPV vaccination.

Impact of human papillomavirus vaccination on racial/ethnic disparities in vaccine-type human papillomavirus prevalence among 14–26 year old females in the U.S.

BackgroundLow human papillomavirus (HPV) vaccination rates early after introduction, particularly among low income and minority adolescents, may have resulted in disparities in vaccine-type HPV prevalence (types 6, 11, 16, 18). The purpose of this study was to examine racial/ethnic variations in HPV prevalence, and evaluate how HPV vaccination has affected vaccine-type HPV prevalence across time. MethodsThis study was a retrospective analysis of 6 cycles of the National Health and Nutrition Examination Survey (NHANES) data (2003–2014). Results on HPV status from vaginal samples of 14–26 year old females who responded about HPV vaccination were used to determine HPV prevalence. Prevaccine HPV prevalence was compared to post-licensure prevalence. Racial/ethnic comparisons were made across time, and models were developed to examine the role of HPV vaccination in observed variations for vaccine-type HPV prevalence. ResultsAmong 4080 females, 29.7% were black, 25.6% were Mexican American, 8.9% were Hispanic, and 35.8% were white. Compared to prevaccine years (2003–2006), vaccine-type HPV did not decrease until late post-licensure years (2011–2014; 14.2% vs. 5.2%, p < 0.001). Most of the decrease occurred among white females between prevaccine and late post-licensure periods (15.2% vs. 4.1%, p < 0.001). Although a decrease in prevalence was observed among black females during the same periods (16.9% vs. 9.8%, p < 0.05), it was not as large as among white females. Prevalence decreased among Mexican Americans (8.2 vs. 4.0, p > 0.05) during the same periods, but the difference was not significant. Interactions between race and time were significant (p < 0.001), with uneven vaccination between black and white females contributing to the disparities observed. ConclusionsHPV vaccination was low in among black and Mexican American females, which contributed to disparities in HPV prevalence. Increasing vaccination among all adolescents, particularly 11–12 year olds, is important because most children this age will not have been exposed.

Change in Human Papillomavirus Prevalence Among U.S. Women Aged 18-59 Years, 2009-2014.

To examine changes in prevalence of vaginal human papillomavirus (HPV) between 2009-2010 and 2013-2014 among both vaccinated and unvaccinated U.S. women. We evaluated HPV prevalence among women 18-59 years old using cross-sectional survey data from three different cycles of the National Health and Nutrition Examination Survey. Data were stratified into four age groups (18-26, 27-34, 35-44, and 45-49 years) to examine trends over time among women of different ages in the postvaccine era. Multivariable analyses, which controlled for descriptive variables, were used to examine the prevalence of quadrivalent vaccine-type HPV by vaccination status. We observed a significant decrease in the prevalence of vaccine-type HPV among women 18-59 years of age from 2009-2010 to 2013-2014. This decline was only significant in those 18-26 years old when the sample was stratified into the four age groups. Among vaccinated 18-26 year olds, HPV prevalence remained low from 2009-2010 (3.9%) to 2013-2014 (2.0%; prevalence ratio 0.51, 95% CI 0.18-1.46). Unvaccinated women 18-26 years old also demonstrated a significant decrease over time from 19.5% in 2009-2010 to 9.7% in 2013-2014 (prevalence ratio 0.44, 95% CI 0.22-0.91). Prevalence did not significantly change among unvaccinated women 26 years old or older. The decline in HPV infections among unvaccinated 18- to 26-year-old women suggests that young women in the United States are beginning to benefit from herd immunity resulting from the introduction of the HPV vaccine.

Effectiveness of Human Papillomavirus Vaccination on Prevalence of Vaccine Genotypes in Young Sexually Active Women in France.

Effectiveness of human papillomavirus (HPV) vaccines in the context of both guidelines, which recommend vaccination at 14 years and modest vaccine coverage, is poorly documented. Residual specimens from females aged <25 years undergoing chlamydia testing were collected, together with demographic, sexual behavior, and vaccine status data. Human pappilomavirus genotypes were determined using the PapilloCheck test system. We compared vaccine type (VT; types 6, 11, 16, 18) prevalence according to vaccination status and identified factors associated with VT prevalence. Of 3736 eligible samples, 822 were from vaccinated women according to immunization record, 1021 from women self-reporting vaccination, and 1893 from unvaccinated women. Adjusted vaccine effectiveness for confirmed vaccinated compared with unvaccinated women was 95.93% (95% confidence interval [CI] = 90.22-98.32) against VT HPV and 38.37% (95% CI = 12.68-56.51) against cross-reactive genotypes (HPV 31, 33, 45), respectively. Vaccine type HPV prevalence was significantly lower (0.61%) among confirmed-vaccinated women than among those who self-reported vaccination or unvaccinated women (1.76% and 15.0%, respectively). Factors associated with prevalent VT in multivariable analysis were vaccine status, positive Chlamydia trachomatis and ≥4 partners in the preceding year. Our study demonstrates evidence of high effectiveness of HPV prophylactic vaccines at an individual level, supporting that wider implementation will help to reduce cervical cancer and precursors incidence.

Prevalence of Human Papillomavirus in Self-Collected Cervicovaginal Swabs in Young Women in the United States Between 2003 and 2012.

To evaluate whether there was a change in prevalence of human papillomavirus (HPV) in the United States correlated with the introduction of HPV vaccines in both vaccinated and unvaccinated women. We performed a retrospective review of prevalence data for women aged 18-29 years living in the United States using the National Health and Nutrition Examination Surveys, which is an ongoing series of cross-sectional surveys. Participants provided responses to standardized questions and self-collected cervicovaginal swabs in which a Linear Array HPV Assay was used to determine HPV prevalence. A total of 783 women from the prevaccine era (2003-2004) and 1,526 from the postvaccine era (2007-2012) were analyzed. Among women aged 18-29 years, the prevalence of vaccine-type HPV declined among women receiving one or more doses of vaccine (P=.003): 10.1% (95% confidence interval [CI] 7.1-13.8%) in the prevaccine era to 4.2% (95% CI 3.3-10.9%) in the postvaccine era. There was no change in prevalence of nonvaccine-type HPV among women receiving one or more doses of vaccine (P>.05). There was also no change in prevalence of vaccine-type HPV among unvaccinated women from the prevaccine era 10.1% (95% CI 7.1-13.8%) to 8.8% (95% CI 5.6-12.9%) in the postvaccine era (P=.4). Vaccine coverage increased to 31.5% of eligible women aged 18-29 years as of 2011-2012. Six years after introduction of HPV vaccination in the United States, there has been a decrease in the prevalence of vaccine-type HPV among women correlated with receiving one or more vaccine doses with no change in nonvaccine-type HPV. Furthermore, there has been no change in prevalence of vaccine-type HPV among unvaccinated women.

Reduction in Vaccine-Type Human Papillomavirus Prevalence Among Women in the United States, 2009-2012.

Between 2009 and 2012, the proportion of young women in the United States completing the human papillomavirus (HPV) vaccine doubled. To understand how quickly this increased uptake is affecting women in the United States, we evaluated the prevalence of vaccine-type (VT) HPV strains among young women in national data sets from 2009-2010 and 2011-2012. Among 18-26-year-old women, the prevalence of VT HPV decreased markedly over a short interval, from 15.4% in 2009-2010 to 8.5% in 2011-2012 (prevalence ratio, 0.51; 95% confidence interval, .28-.92), and the prevalence of high-risk VT HPV decreased from 13.1% to 6.5% (0.46; .25-.86). Reductions in HPV-related diseases will probably follow.

Substantial Decline in Vaccine-Type Human Papillomavirus (HPV) Among Vaccinated Young Women During the First 8 Years After HPV Vaccine Introduction in a Community.

Human papillomavirus (HPV) vaccine effectiveness and herd protection are not well established in community settings. Our objective was to determine trends in vaccine-type HPV in young women during the 8 years after vaccine introduction, to assess changes in HPV prevalence and characterize herd protection in a community. We recruited 3 samples of sexually experienced, 13-26-year-old adolescent girls and young women (hereafter women; N = 1180) from 2006-2014: before widespread vaccine introduction (wave 1) and 3 (wave 2) and 7 (wave 3) years after vaccine introduction. We determined the prevalence of vaccine-type HPV (HPV-6, -11, -16, and -18) among all, vaccinated, and unvaccinated women at waves 1, 2, and 3, adjusted for differences in participant characteristics, then examined whether changes in HPV prevalence were significant using inverse propensity score-weighted logistic regression. Vaccination rates increased from 0% to 71.3% across the 3 waves. Adjusted vaccine-type HPV prevalence changed from 34.8% to 8.7% (75.0% decline) in all women, from 34.9% to 3.2% (90.8% decline) in vaccinated women, and from 32.5% to 22.0% (32.3% decline) in unvaccinated women. Among vaccinated participants, vaccine-type HPV prevalence decreased significantly from wave 1 to wave 2 (adjusted odds ratio, 0.21; 95% confidence interval, .13-.34) and from wave 1 to wave 3 (0.06; .03-.13). The same decreases were also significant among unvaccinated participants (adjusted odds ratios, 0.44; [95% confidence interval, .27-.71] and 0.59; [.35-.98], respectively). The prevalence of vaccine-type HPV decreased >90% in vaccinated women, demonstrating high effectiveness in a community setting, and >30% in unvaccinated women, providing evidence of herd protection.

HPV infections among teen girls on the decline

A study analyzing the prevalence of human papillomavirus (HPV) in girls and women before and after the introduction of the HPV vaccine in 2006 shows that vaccinetype HPV prevalence has decreased 56% percent among girls aged 14 to 19 years. The study shows that the vaccine works well and that the nation needs to increase vaccination rates, according to Centers for Disease Control and Prevention (CDC) director Tom Frieden, MD, MPH. He adds that only one-third of girls aged 13 to 17 years in the United States have been fully vaccinated against HPV, representing 50,000 girls alive today who will develop cervical cancer in their lifetime due to low vaccination rates. The study, conducted by Lauri Markowitz, MD, and her colleagues at the CDC, was published in the Journal of Infectious Diseases.1 The researchers used the National Health and Nutrition Examination Survey (NHANES) data to compare prevalence (or the percentage of girls and women aged 14 to 59 years with certain types of HPV) before the start of the vaccination program (2003-2006) with the prevalence after vaccine introduction (2007-2010). The study also confirmed the results of the clinical trials conducted before the vaccine was licensed, demonstrating that it was highly effective. The decline in HPV vaccine-type prevalence is higher than experts expected, says Dr. Markowitz. She attributes it to herd immunity, high effectiveness with less than a complete 3-dose series, and/or changes in sexual behavior that could not be measured. Nevertheless, public health experts and clinicians hope to see more individuals become vaccinated against the virus. Although routine vaccination for both boys and girls at ages 11 and 12 years is recommended, only approximately onehalf of all girls in the United States and far fewer boys received the first dose of HPV vaccine.

Reduction in Human Papillomavirus (HPV) Prevalence Among Young Women Following HPV Vaccine Introduction in the United States, National Health and Nutrition Examination Surveys, 2003–2010

Human papillomavirus (HPV) vaccination was introduced into the routine immunization schedule in the United States in late 2006 for females aged 11 or 12 years, with catch-up vaccination recommended for those aged 13-26 years. In 2010, 3-dose vaccine coverage was only 32% among 13-17 year-olds. Reduction in the prevalence of HPV types targeted by the quadrivalent vaccine (HPV-6, -11, -16, and -18) will be one of the first measures of vaccine impact. We analyzed HPV prevalence data from the vaccine era (2007-2010) and the prevaccine era (2003-2006) that were collected during National Health and Nutrition Examination Surveys. HPV prevalence was determined by the Linear Array HPV Assay in cervicovaginal swab samples from females aged 14-59 years; 4150 provided samples in 2003-2006, and 4253 provided samples in 2007-2010. Among females aged 14-19 years, the vaccine-type HPV prevalence (HPV-6, -11, -16, or -18) decreased from 11.5% (95% confidence interval [CI], 9.2-14.4) in 2003-2006 to 5.1% (95% CI, 3.8-6.6) in 2007-2010, a decline of 56% (95% CI, 38-69). Among other age groups, the prevalence did not differ significantly between the 2 time periods (P > .05). The vaccine effectiveness of at least 1 dose was 82% (95% CI, 53-93). Within 4 years of vaccine introduction, the vaccine-type HPV prevalence decreased among females aged 14-19 years despite low vaccine uptake. The estimated vaccine effectiveness was high.

Vaccine-Type Human Papillomavirus and Evidence of Herd Protection After Vaccine Introduction

The aims of this study were to compare prevalence rates of human papillomavirus (HPV) in young women before and after HPV vaccine introduction to determine the following: (1) whether vaccine-type HPV infection decreased, (2) whether there was evidence of herd protection, and (3) whether there was evidence for type-replacement (increased prevalence of nonvaccine-type HPV). Young women 13 to 26 years of age who had had sexual contact were recruited from 2 primary care clinics in 2006-2007 for a prevaccination surveillance study (N = 368, none were vaccinated) and 2009-2010 for a postvaccination surveillance study (N = 409, 59% were vaccinated). Participants completed a questionnaire and were tested for cervicovaginal HPV DNA. HPV prevalence rates were compared in the pre- versus postsurveillance studies by using χ(2) tests. Propensity score weighting was used to balance differences in covariates between the 2 surveillance studies. The mean age was ∼19 years for both groups of participants and most were African American and non-Hispanic. After propensity score weighting, the prevalence rate for vaccine-type HPV decreased substantially (31.7%-13.4%, P < .0001). The decrease in vaccine-type HPV not only occurred among vaccinated (31.8%-9.9%, P < .0001) but also among unvaccinated (30.2%-15.4%, P < .0001) postsurveillance study participants. Nonvaccine-type HPV increased (60.7%-75.9%, P < .0001) for vaccinated postsurveillance study participants. Four years after licensing of the quadrivalent HPV vaccine, there was a substantial decrease in vaccine-type HPV prevalence and evidence of herd protection in this community. The increase in nonvaccine-type HPV in vaccinated participants should be interpreted with caution but warrants further study.

Human papillomavirus vaccine introduction in low-income and middle-income countries: guidance on the use of cost-effectiveness models

BackgroundThe World Health Organization (WHO) recommends that the cost effectiveness of introducing human papillomavirus (HPV) vaccination is considered before such a strategy is implemented. However, developing countries often lack the technical capacity to perform and interpret results of economic appraisals of vaccines. To provide information about the feasibility of using such models in a developing country setting, we evaluated models of HPV vaccination in terms of their capacity, requirements, limitations and comparability.MethodsA literature review identified six HPV vaccination models suitable for low-income and middle-income country use and representative of the literature in terms of provenance and model structure. Each model was adapted by its developers using standardised data sets representative of two hypothetical developing countries (a low-income country with no screening and a middle-income country with limited screening). Model predictions before and after vaccination of adolescent girls were compared in terms of HPV prevalence and cervical cancer incidence, as was the incremental cost-effectiveness ratio of vaccination under different scenarios.ResultsNone of the models perfectly reproduced the standardised data set provided to the model developers. However, they agreed that large decreases in type 16/18 HPV prevalence and cervical cancer incidence are likely to occur following vaccination. Apart from the Thai model (in which vaccine and non-vaccine HPV types were combined), vaccine-type HPV prevalence dropped by 75% to 100%, and vaccine-type cervical cancer incidence dropped by 80% to 100% across the models (averaging over age groups). The most influential factors affecting cost effectiveness were the discount rate, duration of vaccine protection, vaccine price and HPV prevalence. Demographic change, access to treatment and data resolution were found to be key issues to consider for models in developing countries.ConclusionsThe results indicated the usefulness of considering results from several models and sets of modelling assumptions in decision making. Modelling groups were prepared to share their models and expertise to work with stakeholders in developing countries.Please see related article: http://www.biomedcentral.com/1741-7007/9/55

Rates of Human Papillomavirus Vaccination, Attitudes About Vaccination, and Human Papillomavirus Prevalence in Young Women

To estimate rates of human papillomavirus (HPV) vaccination, factors associated with intention and belief in one's ability (self-efficacy) to receive the vaccine, and prevalence of vaccine-type HPV during the first year after an HPV-6, HPV-11, HPV-16, HPV-18 vaccine was licensed. Sexually experienced females 13-26 years of age (N=409) were recruited from three primary care clinics, completed a questionnaire, and underwent cervicovaginal HPV DNA testing. Outcome measures were HPV vaccination, intention and belief in one's ability to receive the HPV vaccine in the next year, and prevalence of vaccine-type HPV. Factors independently associated with intention and belief in one's ability to receive the HPV vaccine were determined by logistic regression. Five percent of participants had received at least one HPV vaccine dose, 66% intended to receive the vaccine, 65% were confident they could find the time to get vaccinated, 54% believed that they could receive all three shots, and 42% believed that they could afford vaccination. Sixty-eight percent of women were HPV-positive: 9% for HPV-6, 3% for HPV-11, 17% for HPV-16, and 12% for HPV-18. Factors independently associated with intention included believing that influential people would approve of vaccination, higher perceived severity of cervical cancer or genital warts, fewer safety barriers, and pregnancy history. Factors associated with a high belief in one's ability to receive the vaccine included perceived severity of HPV, sexually transmitted disease history, insurance coverage, and fewer practical barriers to vaccination. Interventions that aim to increase intention and belief in one's ability to receive HPV vaccines, which may lead to higher vaccination rates, should address personal beliefs about vaccination as well as systemic barriers to vaccination. III.