Reduction in HPV 16/18 prevalence in sexually active young women following the introduction of HPV immunisation in England

How has post-implementation surveillance of high-coverage vaccination with HPV16/18-AS04 vaccine in England added to evidence about its cross-protective effects?

BACKGROUND

Bivalent human papillomavirus HPV16/18-AS04 vaccine (Cervarix, GSK) offers direct protection against HPV16/18. Results from randomised controlled trials showed cross protective effects and suggested that declines in some closely related HPV types could be expected in a population with high vaccination coverage.

AIM

To evaluate the evidence for cross-protection afforded by HPV16/18-AS04 from post-implementation surveillance in England, and how this complements clinical trial data and post-implementation observations in other countries.

METHODS

Evidence of cross-protection in young women offered vaccination with HPV16/18-AS04 was gathered from HPV surveillance in England. Data from clinical trials and other post-implementation studies were reviewed.

RESULTS

Surveillance using anonymised residual specimens in England found declines of 52.3%, 67.4% and 33.3% against grouped HPV-31/33/45 in 16-18, 19-21, and 22-24 year olds, respectively. Additionally, type-specific analysis found that the prevalence of HPV31 declined to below 1% across all age groups. Cross-protection has been monitored and maintained for over 10 years since the introduction of the vaccination programme. Cross-protection against HPV6/11 was not found in English surveillance outcomes.

CONCLUSION

Surveillance of type-specific infections in vaccine-eligible populations in England has generated clear evidence of cross-protective effects from HPV16/18-AS04 vaccination against high-risk HPV 31/33/45 infections, consistent with other post-implementation observations and confirming and in some ways exceeding expectations from clinical trials.

The impact of over ten years of HPV vaccination in England: Surveillance of type-specific HPV in young sexually active females

INTRODUCTION

The UK national human papillomavirus (HPV) vaccination programme was introduced in 2008 using the bivalent HPV16/18 vaccine, changing to the quadrivalent HPV6/11/16/18 vaccine from 2012. We provide an analysis of type-specific HPV prevalence in young sexually active females in England to end 2020 (when the first routinely HPV vaccinated females were reaching 25 years of age and entering the National Health Service Cervical Screening Programme), showing the impact of over ten years of high coverage HPV vaccination.

METHODS

Residual vulvovaginal swabs (VVS) were collected from 16 to 24 year old women attending for chlamydia screening between 2010 and 2020, anonymised and tested for type-specific HPV DNA. Trends in vaccine and non-vaccine HPV type prevalence were compared over time and association with vaccination coverage was evaluated within the post-vaccination period.

RESULTS

A total of 21,168 eligible VVS specimens were tested for HPV DNA. The prevalence of HPV16/18 in sexually active 16-18 year old females who were offered vaccination aged 12-13 years was <1% in the most recent years tested, compared to over 15% prior to the vaccination programme in 2008. The magnitude of these decreases also suggests reduced transmission is offering some herd protection to unvaccinated females. HPV31/33/45 prevalence also steadily decreased, providing evidence of cross-protection. HPV6/11 prevalence remained stable during the bivalent vaccine period, with more recent declines, as expected due to the use of the quadrivalent vaccine. There has been no substantive increase in the prevalence of other high-risk (HR) HPV types.

DISCUSSION

More than ten years of high coverage HPV vaccination in adolescent females in England has delivered dramatic declines in the prevalence of HPV vaccine-types and closely related HPV types in females in the vaccine eligible age group, and no indication of type replacement. These findings should enable confidence in planning for cervical screening of these females, and in predicting declines in HPV-related cancers.

Molecular diagnostics of infectious disease: Detection and characterization of microbial agents in cytology samples

BACKGROUND

Cytology samples are widely used to diagnose various infectious diseases by detection and identification of causative infectious agents, including bacteria, fungi, and viruses. The role of cytopathology in infectious disease has expanded tremendously in the past decades with the advances in molecular techniques. Molecular diagnostic methods, compared to conventional methods, have shown improved patient outcome, reduction in cost, and shortened hospital stay times. The aim of this article is to review molecular testing in cytology samples for diagnosis of infectious diseases.

METHODS

The literature search for molecular testing in common cytology samples for diagnosis of infectious diseases was performed. The findings of the studies were summarized. The common cytology samples included in this article were gynecologic specimens, cerebrospinal fluid, bronchoalveolar lavage, and urine samples.

CONCLUSIONS

There are a number of molecular diagnostic tests that are available to be used in common cytology samples to detect infectious agents. Each test has its own advantages and limitations. It is our hope that upon reading this review article, the readers will have better understanding of molecular diagnostic testing of infectious diseases utilizing commonly sampled cytology specimens in daily practice.

Can human papillomavirus vaccination during pregnancy result in miscarriage and stillbirth? A meta-analysis and systematic review

INTRODUCTION

Contradictory results regarding the safety of human papillomavirus (HPV) vaccination during pregnancy have been obtained, which has cast doubt on the use of this method. This review and meta-analysis were conducted to evaluate the safety of HPV vaccination during pregnancy.

METHODS

Complying with the inclusion and exclusion criteria, we searched Web of Science, Scopus, Medline, EMBASE, PubMed and Google Scholar databases for articles published in the past decade using the following keywords: 'papilloma human virus', 'HPV vaccine', 'pregnancy' and 'safety and prevention'. The minimum report quality of the articles was 16 based on the STROBE checklist.

RESULTS

Seven articles were included in the study, three of which were included in the meta-analysis, and the rest were reviewed systematically. The results of the meta-analysis showed that vaccination against HPV during pregnancy or around this period does not increase the risk of miscarriage (RR=2.01; 95% CI: 0.66-6.13) and stillbirth (RR=2.02: 95% CI: 0.65-6.27). No significant difference between miscarriage and stillbirth was observed in women vaccinated against HPV versus those not vaccinated.

CONCLUSIONS

The study of 1380424 individuals showed that HPV vaccination during pregnancy is better postponed until after this period. However, no significant evidence was found to indicate that vaccination was dangerous and unsafe during pregnancy. Further studies are needed to draw a more definitive conclusion.

Reduction in Vaccine HPV Type Infections in a Young Women Group (18-25 Years) Five Years after HPV Vaccine Introduction in Colombia

In Colombia, the human papillomavirus (HPV) vaccine was launched in 2012 in the context of a school-based national vaccination program targeting girls ages 9 to 14 and offering catch-up vaccination for girls ages 14 to 17. In this study, we evaluated the program's impact on type-specific HPV infection by comparing HPV cervical prevalence among vaccinated and nonvaccinated women. This is a comparative cross-sectional study conducted 5 years after the quadrivalent HPV vaccination implementation in a sentinel Colombian City. This study included young women (18-25 years old) who had been vaccinated in the catch-up group and were attending universities and technical institutions, and women who attended primary health care facilities for Pap smear screening. The HPV prevalence of 1,287 unvaccinated women was compared with the prevalence of 1,986 vaccinated women. The prevalence of HPV16/18 infections was significantly lower in vaccinated compared with unvaccinated women (6.5% vs. 15.4%; P < 0.001), whereas for HPV6/11 infections, a decrease of 63.7% in vaccinated women (1.02% vs. 2.81%) was observed. The adjusted effectiveness to HPV16/18 was 61.4%; 95% CI, 54.3%-67.6%. However, the effectiveness against HPV16/18 was significantly higher among women vaccinated before their sexual debut 91.5%; 95% CI, 86.8-94.5, compared with effectiveness for vaccination after their sexual debut, 36.2%; 95% CI, 23.6-46.7. Five years after the introduction of HPV vaccines in Colombia, high effectiveness of HPV to prevent HPV16/18 infections is observed in the catch-up cohorts including virgin and sexually active women. PREVENTION RELEVANCE: Monitoring HPV vaccines post-licensure plays an important role in assessing the progress of immunization programs, demonstrating the impact of vaccines on the population, and providing data for policy needs. In Colombia, HPV vaccines showed effectiveness when administered before start of sexual activity, and two doses are sufficient to achieve good protection.

Effectiveness of various human papillomavirus vaccination strategies: A community randomized trial in Finland

INTRODUCTION

We conducted a community-randomized trial (NCTBLINDED) in Finland to assess gender-neutral and girls-only vaccination strategies with the AS04-adjuvanted human papillomavirus (HPV)-16/18 (AS04-HPV-16/18)vaccine.

METHODS

Girls and boys (12-15 years) were invited. We randomized 33 communities (1:1:1 ratio): Arm A: 90% of randomly selected girls and boys received AS04-HPV-16/18 vaccine and 10% received hepatitis B vaccine (HBV); Arm B: 90% of randomly selected girls received AS04-HPV-16/18 vaccine, 10% of girls received HBV, and all boys received HBV; Arm C: all participants received HBV. Effectiveness measurements against prevalence of HPV-16/18 cervical infection were estimated in girls at 18.5 years. The main measures were: (1) overall effectiveness comparing Arms A or B, regardless of vaccination status, vs Arm C; (2) total effectiveness comparing AS04-HPV-16/18 vaccinated girls in pooled Arms A/B vs Arm C; (3) indirect effectiveness (herd effect) comparing girls receiving HBV or unvaccinated in Arm A vs Arm C. Co-primary objectives were overall effectiveness following gender-neutral or girls-only vaccination.

RESULTS

Of 80,272 adolescents invited, 34,412 were enrolled. Overall effectiveness was 23.8% (95% confidence interval: -19.0, 51.1; P = 0.232) with gender-neutral vaccination. Following girls-only vaccination, overall effectiveness was 49.6% (20.1, 68.2; P = 0.004). Total effectiveness was over 90% regardless of vaccination strategy. No herd effect was found. Immunogenicity of the AS04-HPV-16/18 vaccine was high in both sexes.

CONCLUSIONS

This study illustrates the difficulty in conducting community randomized trials. It is not plausible that vaccinating boys would reduce overall effectiveness, and the apparent lack of herd effect was unexpected given findings from other studies. This analysis was likely confounded by several factors but confirms the vaccine's high total effectiveness as in clinical trials.

Systematic literature review of cross-protective effect of HPV vaccines based on data from randomized clinical trials and real-world evidence

BACKGROUND

The extent of cross-protection provided by currently licensed bivalent and quadrivalent HPV vaccines versus direct protection against HPV 31-, 33-, 45-, 52-, and 58-related disease is debated. A systematic literature review was conducted to establish the duration and magnitude of cross-protection in interventional and observational studies.

METHODS

PubMed and Embase databases were searched to identify randomized controlled trials (RCT) and observational studies published between 2008 and 2019 reporting on efficacy and effectiveness of HPV vaccines in women against non-vaccine types 31, 33, 45, 52, 58, and 6 and 11 (non-bivalent types). Key outcomes of interest were vaccine efficacy against 6- and 12-month persistent infection or genital lesions, and type-specific genital HPV prevalence or incidence. RCT data were analyzed for the according-to-protocol (bivalent vaccine) or negative-for-14-HPV-types (quadrivalent vaccine) efficacy cohorts.

RESULTS

Data from 23 RCTs and 33 observational studies evaluating cross-protection were extracted. RCTs assessed cross-protection in post-hoc analyses of small size subgroups. Among fully vaccinated, baseline HPV-naïve women, the bivalent vaccine showed statistically significant cross-protective efficacy, although with wide confidence intervals, against 6-month and 12-month persistent cervical infections and CIN2+ only consistently for HPV 31 and 45, with the highest effect observed for HPV 31 (range 64.6% [95% CI: 27.6 to 83.9] to 79.1% [97.7% CI: 27.6 to 95.9] for 6-month persistent infection; maximal follow-up 4.7 years). No cross-protection was shown in extended follow-up. The quadrivalent vaccine efficacy reached statistical significance for HPV 31 (46.2% [15.3-66.4]; follow-up: 3.6 years). Similarly, observational studies found consistently significant effectiveness only against HPV 31 and 45 with both vaccines.

CONCLUSIONS

RCTs and observational studies show that cross-protection is inconsistent across non-vaccine HPV types and is largely driven by HPV 31 and 45. Furthermore, existing data suggest that it wanes over time; its long-term durability has not been established.

Immunogenicity and safety of a nine-valent human papillomavirus vaccine in women 27-45 years of age compared to women 16-26 years of age: An open-label phase 3 study

BACKGROUND

Efficacy of the nine-valent human papillomavirus (9vHPV; HPV types 6/11/16/18/31/33/45/52/58) vaccine was demonstrated in a phase 3 study in women 16-26 years of age. We present a phase 3 immunogenicity and safety study of the 9vHPV vaccine in women 27-45 versus 16-26 years of age.

METHODS

This international, open-label study (NCT03158220) was conducted in women 16-45 years of age. Participants (16-26 years, n = 570 and 27-45 years, n = 642) received a three-dose 9vHPV vaccination regimen (day 1, month 2, month 6). Month 7 geometric mean titers (GMTs) and seroconversion percentages to anti-HPV 6/11/16/18/31/33/45/52/58 were assessed. Participants were followed for safety throughout the study.

RESULTS

At month 7, anti-HPV 6/11/16/18/31/33/45/52/58 GMTs in women 27-45 years were compared to those in women 16-26 years of age. The primary hypothesis of non-inferiority of anti-HPV 16/18/31/33/45/52/58 GMTs in older versus younger women was met. The lower bound of the GMT ratio 95% confidence interval (27-45 years to 16-26 years) was 0.60-0.67 depending on HPV type, exceeding the non-inferiority margin of 0.5 for all HPV types. Month 7 seroconversion percentages in women 27-45 years of age were >99% for all HPV types. Injection-site and vaccine-related systemic adverse events (AEs) were observed in 87.5% and 25.1% of women 16-26 years, and 85.2% and 24.1% of women 27-45 years of age, respectively; no vaccine-related serious AEs were reported and no deaths occurred during the study.

CONCLUSIONS

The 9vHPV vaccine elicited non-inferior anti-HPV GMTs in women 27-45 years compared with women 16-26 years of age for HPV 16/18/31/33/45/52/58. The vaccine was generally well tolerated with a similar AE profile across the age groups. These data support bridging 9vHPV vaccine efficacy findings in women 16-26 years to women 27-45 years of age. Clinical trial registration NCT03158220.

Current and future vaccine clinical research with the licensed 2-, 4-, and 9-valent VLP HPV vaccines: What's ongoing, what's needed?

Prophylactic HPV vaccination has been a great public health success. For >20 years, clinical trials were conducted with the 2-, 4-, and/or 9-valent vaccines in young-adult females, mid-adult women, males, and adolescents. In all studies, the vaccines were highly efficacious, immunogenic, and well tolerated. Following vaccine licensure and utilization in national vaccine programs globally (real-world settings primarily in high income countries), numerous studies demonstrated that the vaccines continue to have an excellent safety profile and have dramatically reduced the incidence of genital warts, HPV vaccine-type prevalence, and precancerous lesions. Thirty-eight clinical trials with the currently licensed HPV vaccines are ongoing. Key questions being addressed in new trials include: efficacy against persistent infection and immunogenicity of a 1-dose regimen; efficacy of 3 doses in 20-45-year-old females; use in postpartum women and immunocompromised individuals (HIV, liver and kidney transplants); dose sparing via intradermal administration; use in combination with a PD1 monoclonal antibody in patients with cervical cancer; impact on recurrent disease in women undergoing cervical conization; persistence of protection; and use to prevent oropharyngeal cancer. Additional clinical research that should be conducted includes: long-term follow-up, particularly of 1- and 2-dose regimens; further evaluation of flexible 2-dose regimens; immunogenicity of 1- or 2-dose regimens in persons ≥15 years old and immunocompromised populations; safety and immunogenicity of 1 or 2 doses in children <9 years old; assessment of the vaccine in the prevention of transmission; interchangeability with newer HPV vaccines; additional concomitant use studies; and prevention of penile cancer and recurrent respiratory papillomatosis.

Human Papillomavirus Selected Properties and Related Cervical Cancer Prevention Issues

High-risk human papillomavirus strains are widely known to be the causative agents responsible for cervical cancer development. Aggregated damage caused by papillomaviruses solely is estimated in at least 5% of all malignancies of the human body and 16% in cancers that affect the female genital area. Enhanced understanding of the complex issue on how the high extent of carcinogenicity is eventually formed due to the infection by the Papoviridae family would contribute to enhancing current prevention strategies not only towards cervical cancer, but also other HPV associated cancers. This review article is aimed at presenting the key points in two directions: the current cervical cancer prevention and related aspects of HPV behavior. Virtually all applied technologies related to HPV diagnostics and screening programs, such as HPV tests, colposcopy-based tests (VIA/VILI), conventional and liquid-based cytology, currently available are presented. Issues of availability, advantages, and drawbacks of the screening programs, as well as vaccination strategies, are also reviewed in the article based on the analyzed sources. The current point of view regarding HPV is discussed with emphasis on the most problematic aspect of the HPV family concerning the observed increasing number of highly carcinogenic types. Present trends in HPV infection diagnostics throughout the human fluids and tissues are also reported, including the latest novelties in this field, such as HPV assay/self-sample device combinations. Besides, a brief outline of the related prevention issues in Kazakhstan, the leading country of Central Asia, is presented. Kazakhstan, as one of the post-soviet middle-income countries, may serve as an example of the current situation in those terrains, concerning the implementation of globally accepted cervical cancer prevention strategies. Along with positive achievements, such as the development of a nationwide screening program, a range of drawbacks is also analyzed and discussed.

Effectiveness of HPV vaccination against the development of high-grade cervical lesions in young Japanese women

BACKGROUND

Although more than 10 years have passed since HPV vaccination was implemented, first as an interim programme (Emergent vaccine promotion programme) in November 2010, followed by incorporating into the National Immunization Programme in April, 2013 and suspended in June 2013, limited studies have investigated the HPV vaccine effectiveness against high-grade cervical lesions in Japan.

METHODS

We collected the matched data of the results of cervical biopsy and history of vaccination from the Japan Cancer Society database. The subjects were women aged 20 to 29 years screened for cervical cancer between April, 2015 and March, 2017, and with information on HPV vaccination status. We estimated the relative risk of developing high-grade cervical lesions in vaccinated subjects using Poisson regression as compared to unvaccinated subjects.

RESULTS

Among the 34,281 women screened, 3770 (11.0%) were vaccinated. The prevalence of CIN2+ was statistically significantly lower in the vaccinated women as compared to the unvaccinated women (Vaccine Effectiveness (VE) =76%; RR = 0.24, 95% CI:0.10-0.60). High VE against CIN3+ was also observed (91%; RR = 0.09, 95% CI:0.00-0.42).

CONCLUSION

Women aged 20-29 years who received at least one dose of HPV vaccine had a significantly lower risk of high-grade cervical lesions than those not vaccinated. In Japan, HPV vaccination should be resumed in order to reduce the incidence of cervical cancer.

Alternative New Mono-scaled Quantitative Benefit-Risk Assessment of Human Papillomavirus Vaccine in Japan

BACKGROUND

The human papillomavirus (HPV) vaccine coverage is very low in Japan since the government suspended the active encouragement of the vaccination. We aimed to conduct a benefit-risk assessment of HPV vaccination and explore different consequent scenarios to identify potential improvements to the current Japanese immunization program.

METHODS

To calculate social benefit-risk of HPV vaccine, we used the Markov model to represent the natural history of HPV and adverse events (AEs) using disability-adjusted life year (DALY) as the outcome. Benefits and risks were calculated as the sum of negative and positive outcomes corresponding to all preventable diseases and AEs associated with HPV vaccination, respectively. The benefit-risk balance in 2050 was estimated using published data.

RESULTS

Our model was confirmed by published cervical cancer incidence and mortality rates. The benefit-risk balance in 2050 showed that the most effective scenario was the introduction of 9-valent HPV vaccine targeting female individuals aged 10-29 years for routine vaccination starting in 2020, although there is possibility of increased risks of AEs for the vaccinated age group post resumption of recommendations.

CONCLUSION

Our benefit-risk assessment of HPV vaccine helped estimate various scenarios pertaining to HPV vaccination and identify the best strategy regarding HPV vaccination. This benefit-risk assessment approach may be used for other vaccines and vaccination programs.

Facilitators and barriers of human papillomavirus vaccine uptake in young females 18-26 years old in Singapore: A qualitative study

BACKGROUND

Around 70% of cervical cancers are caused by Types 16 and 18 of human papillomavirus (HPV). Vaccines against HPV have been shown to be safe and effective in preventing HPV and cervical cancer.

OBJECTIVE

To explore the facilitators and barriers of HPV vaccination in young females aged 18-26 years in Singapore, and to describe their recommended strategies to improve the uptake of HPV vaccination.

DESIGN

Qualitative, descriptive design guided by the socio-ecological model.

PARTICIPANTS

Young women studying in National University of Singapore (NUS), aged 18-26 (N = 40). Purposive sampling was used to recruit participants from various socio-economic levels and faculties, both vaccinated against HPV and unvaccinated.

METHODS

In-depth interviews (IDIs) and focus group discussions (FGDs) were conducted with the participants. IDIs and FGDs were transcribed and coded using NVIVO software. Thematic data analysis was performed using an inductive approach.

RESULTS

Barriers to HPV vaccination included lack of awareness, lack of perceived risk for cervical cancer, cost, lack of parental support, inconvenience of getting the vaccination, stigma associated with connection with sexual activity, and concern regarding safety. Facilitators include parental encouragement, protection of one's health, lack of logistical barriers, and perceived safety and efficacy of the vaccine. Participants recommended increasing awareness of HPV vaccination and cervical cancer, reducing cost of vaccination and making the vaccine compulsory to increase vaccine uptake.

CONCLUSION

Barriers and facilitators exist at different levels to influence vaccine uptake. Public education on cervical cancer and the vaccine should be stepped up to increase public awareness. A school-based national vaccination programme was proposed by the target group to increase the rate of uptake of HPV vaccination in Singapore.

Exploration of the effect of human papillomavirus (HPV) vaccination in a cohort of pregnant women in Montreal, 2010-2016

HPV vaccination efficacy has been shown in clinical trials but it is important to verify population level vaccine effectiveness (VE). We aimed to explore VE and herd effect using HPV infection data from a cohort study of Canadian pregnant women. We analyzed the baseline data of the HERITAGE study, which includes pregnant women recruited in Montreal between 2010-2012 and 2015–2016. Cervicovaginal samples self-collected in the first trimester were tested for 36 HPV types. Vaccination status was self-reported. VE and 95% confidence intervals (CI) were estimated by comparing the prevalence of HPV between vaccinated and unvaccinated women. Herd effect was explored by comparing HPV prevalence in unvaccinated women between the 2 recruitment periods. Adjusted ORs (95%CI) were estimated using exact logistic regression. The proportion of vaccinated women with at least one dose of 4vHPV was 7.5%. Although most of them were vaccinated after the onset of sexual activity, a high VE was found for HPV-16/18 (86.1% (95%CI: 15.0–99.7)). For HPV-6/11/16/18 and for HPV-31/33/45, VE was 61.9% (-23.5–92.6) and 57.0% (-47.7–92.0%), respectively. We also observed a non-statistically significant reduction in the prevalence of HPV-6/11/16/18 and HPV-31/33/45 among unvaccinated women recruited during the second recruitment period (adjusted OR: 0.8 (0.4–1.8) and 0.8 (0.3–1.7), respectively).

Population-level impact and herd effects following the introduction of human papillomavirus vaccination programmes: updated systematic review and meta-analysis

BACKGROUND

More than 10 years have elapsed since human papillomavirus (HPV) vaccination was implemented. We did a systematic review and meta-analysis of the population-level impact of vaccinating girls and women against human papillomavirus on HPV infections, anogenital wart diagnoses, and cervical intraepithelial neoplasia grade 2+ (CIN2+) to summarise the most recent evidence about the effectiveness of HPV vaccines in real-world settings and to quantify the impact of multiple age-cohort vaccination.

METHODS

In this updated systematic review and meta-analysis, we used the same search strategy as in our previous paper. We searched MEDLINE and Embase for studies published between Feb 1, 2014, and Oct 11, 2018. Studies were eligible if they compared the frequency (prevalence or incidence) of at least one HPV-related endpoint (genital HPV infections, anogenital wart diagnoses, or histologically confirmed CIN2+) between pre-vaccination and post-vaccination periods among the general population and if they used the same population sources and recruitment methods before and after vaccination. Our primary assessment was the relative risk (RR) comparing the frequency (prevalence or incidence) of HPV-related endpoints between the pre-vaccination and post-vaccination periods. We stratified all analyses by sex, age, and years since introduction of HPV vaccination. We used random-effects models to estimate pooled relative risks.

FINDINGS

We identified 1702 potentially eligible articles for this systematic review and meta-analysis, and included 65 articles in 14 high-income countries: 23 for HPV infection, 29 for anogenital warts, and 13 for CIN2+. After 5-8 years of vaccination, the prevalence of HPV 16 and 18 decreased significantly by 83% (RR 0·17, 95% CI 0·11-0·25) among girls aged 13-19 years, and decreased significantly by 66% (RR 0·34, 95% CI 0·23-0·49) among women aged 20-24 years. The prevalence of HPV 31, 33, and 45 decreased significantly by 54% (RR 0·46, 95% CI 0·33-0·66) among girls aged 13-19 years. Anogenital wart diagnoses decreased significantly by 67% (RR 0·33, 95% CI 0·24-0·46) among girls aged 15-19 years, decreased significantly by 54% (RR 0·46, 95% CI 0.36-0.60) among women aged 20-24 years, and decreased significantly by 31% (RR 0·69, 95% CI 0·53-0·89) among women aged 25-29 years. Among boys aged 15-19 years anogenital wart diagnoses decreased significantly by 48% (RR 0·52, 95% CI 0·37-0·75) and among men aged 20-24 years they decreased significantly by 32% (RR 0·68, 95% CI 0·47-0·98). After 5-9 years of vaccination, CIN2+ decreased significantly by 51% (RR 0·49, 95% CI 0·42-0·58) among screened girls aged 15-19 years and decreased significantly by 31% (RR 0·69, 95% CI 0·57-0·84) among women aged 20-24 years.

INTERPRETATION

This updated systematic review and meta-analysis includes data from 60 million individuals and up to 8 years of post-vaccination follow-up. Our results show compelling evidence of the substantial impact of HPV vaccination programmes on HPV infections and CIN2+ among girls and women, and on anogenital warts diagnoses among girls, women, boys, and men. Additionally, programmes with multi-cohort vaccination and high vaccination coverage had a greater direct impact and herd effects.

FUNDING

WHO, Canadian Institutes of Health Research, Fonds de recherche du Québec - Santé.

Efficacy, immunogenicity and safety of the AS04-HPV-16/18 vaccine in Chinese women aged 18-25 years: End-of-study results from a phase II/III, randomised, controlled trial

Background

Cervical cancer is a major public health concern in China. We report the end‐of‐study results of a phase II/III trial to assess the efficacy, immunogenicity, and safety of the AS04‐human papillomavirus (HPV)‐16/18 vaccine in Chinese women aged 18‐25 years followed for up to 72 months after first vaccination. Results of approximately 57 months following first vaccination have been previously reported.

Methods

Healthy 18‐25‐year‐old women (N = 6051) were randomized (1:1) to receive three doses of AS04‐HPV‐16/18 vaccine or Al(OH)₃ (control) at Months 0‐1‐6. Vaccine efficacy against HPV‐16/18 infection and cervical intraepithelial neoplasia (CIN), cross‐protective vaccine efficacy against infections and lesions associated with nonvaccine oncogenic HPV types, immunogenicity, and safety were assessed. Efficacy was assessed in the according‐to‐protocol efficacy (ATP‐E) cohort (vaccine N = 2888; control N = 2892), total vaccinated cohort for efficacy (TVC‐E; vaccine N = 2987; control N = 2985) and TVC‐naïve (vaccine N = 1660; control N = 1587).

Results

In initially HPV‐16/18 seronegative/DNA‐negative women, vaccine efficacy against HPV‐16/18‐associated CIN grade 2 or worse was 87.3% (95% CI: 5.5, 99.7) in the ATP‐E, 88.7% (95% CI: 18.5, 99.7) in the TVC‐E, and 100% (95% CI: 17.9, 100) in the TVC‐naïve. Cross‐protective efficacy against incident infection with HPV‐31, HPV‐33 and HPV‐45 was 59.6% (95% CI: 39.4, 73.5), 42.7% (95% CI: 15.6, 61.6), and 54.8% (95% CI: 19.3, 75.6), respectively (ATP‐E). At Month 72, >95% of initially seronegative women who received HPV vaccine in the ATP cohort for immunogenicity (N = 664) remained seropositive for anti‐HPV‐16/18 antibodies; anti‐HPV‐16 and anti‐HPV‐18 geometric mean titers were 678.1 EU/mL (95% CI: 552.9, 831.5) and 343.7 EU/mL (95% CI: 291.9, 404.8), respectively. Serious adverse events were infrequent (1.9% vaccine group [N = 3026]; 2.7% control group [N = 3025]). Three and zero women died in the control group and the vaccine group respectively. New onset autoimmune disease was reported in two women in the vaccine group and two in the control group.

Conclusions

This is the first large‐scale randomized clinical trial of HPV vaccination in China. High and sustained vaccine efficacy against HPV‐16/18‐associated infection and cervical lesions was demonstrated up to Month 72. The vaccine had an acceptable safety profile. Combined with screening, prophylactic HPV vaccination could potentially reduce the high burden of HPV infection and cervical cancer in China.

Trial registration

NCT00779766.

Assessing the cost-effectiveness of HPV vaccination strategies for adolescent girls and boys in the UK

BACKGROUND

Human papillomavirus (HPV) is the most widespread sexually transmitted infection worldwide. It causes several health consequences, in particular accounting for the majority of cervical cancer cases in women. In the United Kingdom, a vaccination campaign targeting 12-year-old girls started in 2008; this campaign has been successful, with high uptake and reduced HPV prevalence observed in vaccinated cohorts. Recently, attention has focused on vaccinating both sexes, due to HPV-related diseases in males (particularly for high-risk men who have sex with men) and an equity argument over equalising levels of protection.

METHODS

We constructed an epidemiological model for HPV transmission in the UK, accounting for nine of the most common HPV strains. We complemented this with an economic model to determine the likely health outcomes (healthcare costs and quality-adjusted life years) for individuals from the epidemiological model. We then tested vaccination with the three HPV vaccines currently available, vaccinating either girls alone or both sexes. For each strategy we calculated the threshold price per vaccine dose, i.e. the maximum amount paid for the added health benefits of vaccination to be worth the cost of each vaccine dose. We calculated results at 3.5% discounting, and also 1.5%, to consider the long-term health effects of HPV infection.

RESULTS

At 3.5% discounting, continuing to vaccinate girls remains highly cost-effective compared to halting vaccination, with threshold dose prices of £56-£108. Vaccination of girls and boys is less cost-effective (£25-£53). Compared to vaccinating girls only, adding boys to the programme is not cost-effective, with negative threshold prices (-£6 to -£3) due to the costs of administration. All threshold prices increase when using 1.5% discounting, and adding boys becomes cost-effective (£36-£47). These results are contingent on the UK's high vaccine uptake; for lower uptake rates, adding boys (at the same uptake rate) becomes more cost effective.

CONCLUSIONS

Vaccinating girls is extremely cost-effective compared with no vaccination, vaccinating both sexes is less so. Adding boys to an already successful girls-only programme has a low cost-effectiveness, as males have high protection through herd immunity. If future health effects are weighted more heavily, threshold prices increase and vaccination becomes cost-effective.

Changes in human papillomavirus genotypes associated with cervical intraepithelial neoplasia grade 2 lesions in a cohort of young women (2013-2016)

In 2008, a quadrivalent human papillomavirus (HPV) vaccine (genotypes 6, 11, 16, 18) became available in New Zealand. This study investigated whether the proportion of cervical intraepithelial neoplasia grade 2 (CIN2) lesions associated with HPV genotypes 16 and 18 changed over time in young women recruited to a prospective CIN2 observational management trial (PRINCess) between 2013 and 2016. Partial HPV genotyping (16, 18, or other high risk HPV) was undertaken on n = 392 women under 25 years (mean age 21.8, range 17–24) with biopsy-diagnosed CIN2. High risk HPV genotypes were detected in 96% of women with CIN2 lesions. Between 2013 and 2016, the proportion of women whose liquid-based cytology samples were HPV 16 or 18 positive decreased from 43% to 13%. HPV vaccination status was known for 78% of women. Between 2013 and 2016, the proportion of HPV 16/18 positivity did not significantly change in HPV-vaccinated women, but decreased from 66% to 17% in unvaccinated women. The reducing proportion of HPV 16/18-related CIN2 in our cohort of young New Zealand women may be attributable to the introduction of a national HPV vaccination program. The substantial decrease in HPV 16/18 positivity observed in unvaccinated women is likely to be due to a herd effect.

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392 women under 25 years with CIN2 lesions were recruited between 2013 and 2016.

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HPV16/18 positivity decreased from 43% of women in 2013–13% in 2016.

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In vaccinated women, HPV16/18 positivity decreased from 17% in 2013 to 9% in 2016.

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In unvaccinated women, HPV16/18 positivity decreased from 66% in 2013 to 17% in 2016.

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Decreasing HPV16/18-related CIN2 may be due to HPV vaccination and herd effect.

Y Chromosome DNA in Women's Vaginal Samples as a Biomarker of Recent Vaginal Sex and Condom Use With Male Partners in the HPV Infection and Transmission Among Couples Through Heterosexual Activity Cohort Study

BACKGROUND

Y chromosome DNA from male epithelial and sperm cells was detected in vaginal samples after unprotected sex in experimental studies. We assessed the strength of this association in an observational setting to examine the utility of Y chromosome DNA as a biomarker of recent sexual behaviors in epidemiological studies.

METHODS

The HPV (human papillomavirus) Infection and Transmission Among Couples Through Heterosexual Activity cohort study enrolled 502 women attending a university or college in Montréal, Canada, and their male partners from 2005 to 2010. Participants completed self-administered questionnaires. We used real-time polymerase chain reaction to test women's baseline vaginal samples for Y chromosome DNA and assessed which sexual behaviors were independent predictors of Y chromosome DNA positivity and quantity with logistic and negative binomial regression.

RESULTS

Y chromosome DNA positivity decreased from 77% in women in partnerships reporting vaginal sex 0 to 1 day ago to 13% in women in partnerships reporting last vaginal sex of 15 or more days ago (adjusted odds ratio, 0.09; 95% confidence interval, 0.02-0.36). The mean proportion of exfoliated vaginal sample cells with Y chromosome DNA was much lower for women who reported always using condoms (0.01%) than for women who reported never using condoms (2.07%) (adjusted ratio, 26.8; 95% confidence interval, 8.9-80.5). No association was found with reported oral/digital sex frequency or concurrency of partnerships.

CONCLUSIONS

Y chromosome DNA quantity is strongly associated with days since last vaginal sex and lack of condom use in observational settings. Y chromosome DNA quantity may prove useful as a correlate of recent vaginal sex in observational studies lacking data on sexual behavior, such as surveillance studies of human papillomavirus infection prevalence.

Direct, indirect and total effectiveness of bivalent HPV vaccine in women in Galicia, Spain

Bivalent human papillomavirus (HPV) vaccine was incorporated into the childhood vaccination calendar in Galicia, Spain in 2008. The objectives of this study were to estimate direct, indirect and total effectiveness of HPV vaccine and to identify sexual habits changes in the post-vaccination period in Galicia, Spain.Endocervical scrapings of 745 women attending 7 Health Areas of the Galician Public Health Service were collected in the post-vaccination period, from 2014-2017. Two groups were studied: women born between 1989 and 1993 (n = 397) and women born in 1994 or later (n = 348). Twelve high-risk human papillomavirus (HR-HPV) genotypes were detected by Cobas® 4800 HPV test (Roche Diagnostics, Mannheim, Germany). The Linear Array® HPV Genotyping Test (Roche Diagnostics) was used for HR-HPV genotype detection other than HPV 16/18. Information about sexual habits was collected by a self-filled questionnaire. Post-vaccination data were compared to previously published pre-vaccination data obtained between 2008 and 2010 in Galicia from women of the same age (18-26 years old, n = 523). The Stata 14.2 software was employed for statistical analyses.Data from 392 unvaccinated and 353 vaccinated women were compared. For unvaccinated and vaccinated women, HPV 16/18 prevalence was 9.2% and 0.8%, respectively, and HPV 31/33/45 prevalence was 8.4% and 1.1%, respectively. Direct, indirect and total effectiveness of the HPV vaccine were (%, 95% CI): 94 (72-99), 30 (-11-56) and 95 (79-99), respectively, for HPV 16/18 and 83 (46-94), -10 (-88-33) and 84 (54-94), respectively, for HPV 31/33/45. The number of women with first intercourse before 17 years old and 3 or more sexual partners along life was higher in the post-vaccination period (p < 0.05). A positive impact of bivalent HPV vaccine was observed, both on direct and cross protection. Sexual habits could have changed in the post-vaccination period.

Frequency and coinfection between genotypes of human papillomavirus in a population of asymptomatic women in northern Peru

Objective

Describe the prevalence of HPV genotypes via PCR and DNA sequencing in 397 women who attended to the gynecological outpatient center in the Hospital Regional Docente de Cajamarca from March to September 2017.

Results

A positive PCR result for HPV was observed in 121 cervical samples. A high-risk genotype was found in 63.6% (77/121) of patients, a probably oncogenic type in 23.1% (28/121) and a low-risk type in 7.4%. Among the high-risk genotypes, HPV-31 was the most common one present in 20% (21/77), followed by HPV-16 in 11.4% (12/77). Coinfections between two or more genotypes were observed in 12 cases.

Electronic supplementary material

The online version of this article (10.1186/s13104-018-3644-7) contains supplementary material, which is available to authorized users.

Prevalence of Vaccine Type Infections in Vaccinated and Non-Vaccinated Young Women: HPV-IMPACT, a Self-Sampling Study

Background: The human papillomavirus (HPV) vaccination program for young girls aged 11⁻26 years was introduced in Switzerland in 2008. The objective of this study was to evaluate the prevalence of high- and low-risk HPV in a population of undergraduate students using self-sampling for monitoring the HPV vaccination program's effect.

METHODS

Undergraduate women aged between 18⁻31 years, attending the Medical School and University of Applied Sciences in Geneva, were invited to participate in the study. Included women were asked to perform vaginal self-sampling for HPV testing using a dry cotton swab.

RESULTS

A total of 409 students participated in the study-aged 18⁻31 years-of which 69% of the participants were vaccinated with Gardasil HPV vaccine and 31% did not received the vaccine. About HPV prevalence, 7.2% of unvaccinated women were HPV 16 or 18 positive, while 1.1% of vaccinated women were infected by HPV 16 or 18 (p < 0.01). Prevalence of HPV 6 and 11 was 8.3% in non-vaccinated women versus 2.1% in vaccinated women (p < 0.02). We observed no cross-protection for the other HPV genotypes of a low- and high-risk strain.

CONCLUSIONS

Prevalence of HPV 6/11/16/18 was lower in vaccinated women versus unvaccinated women. Continued assessment of HPV vaccine effectiveness in real population is needed.

Epidemiology of HPV Infection and HPV-Related Cancers in Kazakhstan: a Review

Background: Cancer is one of the most prevalent causes of mortality worldwide. In the cervix it is considered to be caused by different high-risk human papillomavirus (HPV) types. Although many studies have already been conducted worldwide on the epidemiology of HPV infection and their oncogenic properties, limited data are available on HPV prevalence, incidence and genotype specific dissemination in Kazakhstan. Methods: To review the distribution of HPV infection, electronic databases (e.g. PubMed, Web of Science and Google Scholar) were searched for peer reviewed articles in English. The study was performed during June-July 2017 with a review of 39 relevant articles, published up to July 31, 2017. The following inclusion criteria were applied: general population data, cytology results available, and use of polymerase chain reaction (PCR) and/or Hybrid Capture® 2, Digene Corp., USA for HPV detection. Results: As reported in limited studies, the prevalence of HPV infection in Kazakhstan ranges from 43.8% to 55.8%. However, the scenario with regard to epidemiology of HPV related cancers in Kazakhstan is not very clear. One study reported a decline of laryngeal cancer observed during the recent years, whereas cervical cancer incidence has increased to about 3000 new cervical cancer cases, and about 1,000 cervical cancer deaths each year. Conclusion: The high incidence of cervical cancer with a significant mortality rate in Kazakhstan is evidence of HPV infection abundance despite an absence of HPV screening and low public awareness of the problem. Having a well-informed understanding of the role of HPV infection could enhance the public’s acceptance of screening and intervention programs to reduce morbidity and mortality in the country due to HPV infection. Thus, the purpose of this review article is to summarize the existing data, identifying directions for future research on HPV epidemiology and HPV-related diseases in Kazakhstan.

Lessons learned from domestic and international human papillomavirus vaccination programs: a review

Since the development of the human papillomavirus vaccine, many countries have created implementation programs to bolster vaccination rates and protect their populations. Despite demonstrated efficacy with decreased human papillomavirus-related disease abroad, the vaccine's potential to prevent morbidity and mortality in the United States is not being met. The purpose of this review is to discuss strategies of both international and domestic vaccination programs, their impact on human papillomavirus-related diseases, the unique obstacles faced by the United States, and future directions for success.

HPV primary cervical screening in England: Women's awareness and attitudes

BACKGROUND

Primary human papillomavirus (HPV) cervical screening is due to be implemented in England within the next 2 years; however, the acceptability of HPV testing as the primary screening test is unclear. This study explores women's awareness and attitudes toward HPV testing/screening.

METHODS

Qualitative interviews (semistructured and focus group) were conducted with 46 women (aged 25-65 years) from community and secondary care settings. Data were analyzed by using the inductive-framework method.

RESULTS

Women were unaware that cervical screening currently includes HPV testing and lacked HPV-related knowledge. Emotions of shock, fear, and anxiety were reported upon receiving a positive HPV result. For women in long-term relationships, the realization that HPV is a sexually transmitted infection was seen as a barrier to primary HPV testing. Knowledge that HPV testing is a screening test to prevent cervical cancer did not change their attitudes. Women debated the need for continued screening following a negative result. Women feared judgment by the community if they participated with primary HPV screening because they were being tested for a sexually transmitted infection, with the possible attendant perception that they had adopted a high-risk lifestyle in comparison to nonattenders.

CONCLUSIONS

The acceptability of HPV testing may be a limiting factor in encouraging participation with screening in the future.

Reduction in the burden of hospital admissions due to cervical disease from 2003-2014 in Spain

BACKGROUND

Cervix uteri cancer is the 4th most common cancer among women worldwide and the second most frequent cancer in women under 45 years old in Spain. We aimed to describe the burden of hospital admissions by malignant neoplasia (MN) and in situ carcinoma (ISC) of the cervix in Spain from 2003 to 2014, a 12-year period that included the first years after introduction of an HPV vaccination program.

METHODS

This epidemiological study reviewed data from the Ministry of Health National Surveillance System, which includes more than 98% of Spanish hospitals. Hospitalization rate, mortality rate, and case fatality rates were calculated per year and age group.

RESULTS

We found 74,933 hospitalizations due to MN and ISC of the cervix. The average age at hospitalization increased significantly during the study period. The average length of hospital stay decreased significantly (p<0.001), while hospitalization costs increased. The mean hospitalization rate was 27.532 cases per 100,000 women (95% CI: 27.335-27.729). This rate decreased significantly during the study period. The mean mortality rate was 1.418 deaths per 100,000 women (95% CI: 1.373-1.463) and the mean case-fatality rate was 5.150% (95% CI: 4.992-5.308).

CONCLUSION

Our study showed a substantial decrease in the hospitalization burden due to cervical disease. This decrease could be attributable to different causes including cervical cancer prevention measures, and changes in disease management. Further research is needed to confirm the cause. This information could contribute to further evaluations of the impact and cost effectiveness analysis of HPV vaccination in Spain.

The risky womb and the unthinkability of the pregnant man: Addressing trans masculine hysterectomy

In April 2017, the European Court of Human Rights ruled that requiring trans people to undergo sterilisation in order to grant legal gender recognition was a breach of human rights. In the UK, sterilisation has never been a legal requirement for trans people. However, hysterectomy and salpingo-oopherectomy have been strongly encouraged for trans masculine people on medical grounds, although the clinical evidence for current recommendations is weak. Within this article I analyse the issue from a feminist perspective and argue that current presumptions in favour of surgical intervention are influenced by the history of medical interventions to “fix” bodies perceived as female, coupled with a strong social taboo against the pregnant man. As a consequence, medical and legal frameworks are not necessarily facilitating optimal outcomes for the individual. I suggest that practices in this regard should be critically examined, with a view to developing more tailored, person-centred practices and facilitating informed choice.

Effect of HPV vaccination and cervical cancer screening in England by ethnicity: a modelling study

BACKGROUND

Health equality is increasingly being considered alongside overall health gain when assessing public health interventions. However, the trade-off between the direct effects of vaccination and herd immunity could lead to unintuitive consequences for the distribution of disease burden within a population. We used a transmission dynamic model of human papillomavirus (HPV) to investigate the effect of ethnic disparities in vaccine and cervical screening uptake on inequality in disease incidence in England.

METHODS

We developed an individual-based model of HPV transmission and disease, parameterising it with the latest data for sexual behaviour (from National Survey of Sexual Attitudes and Lifestyles [Natsal-3]) and vaccine and screening uptake by ethnicity (from Public Health England [PHE]) and fitting it to data for HPV prevalence (from ARTISTIC, PHE, Natsal-3) and HPV-related disease incidence (from National Cancer Registry [ONS]). The outcome of interest was the age-adjusted incidence of HPV-related cancer (both cervical and non-cervical) in all women in England in view of differences and changes in vaccination and screening uptake by ethnicity in England, over time. We also studied three potential public health interventions aimed at reducing inequality in HPV-related disease incidence: increasing uptake in black and Asian females to match that in whites for vaccination; cervical screening in women who turn 25 in 2018 or later; and cervical screening in all ages.

FINDINGS

In the pre-vaccination era, before 2008, women from ethnic minorities in England reported a disproportionate share of cervical disease. Our model suggests that Asian women were 1·7 times (95% credibility interval [CI] 1·1-2·7) more likely to be diagnosed with cervical cancer than white women (22·8 vs 13·4 cases per 100 000 women). Because HPV vaccination uptake is lower in ethnic minorities, we predict an initial widening of this gap, with cervical cancer incidence in Asian women up to 2·5 times higher (95% CI 1·3-4·8) than in white women 20 years after vaccine introduction (corresponding to an additional 10·8 [95% CI 10·1-11·5] cases every year). In time, we predict that herd immunity benefits will diffuse from the larger white sub-population and the disparity will narrow. Increased cervical screening uptake in vaccinated women from ethnic minorities would lead to rapid improvement in equality with parity in incidence after 20 years of HPV vaccination.

INTERPRETATION

Our study suggests that the introduction of HPV vaccination in England will initially widen a pre-existing disparity in the incidence of HPV-related cancer by ethnicity, partly due to herd immunity disproportionately benefiting subgroups with high vaccination rates. Although in time this induced disparity will narrow, increasing cervical screening uptake in girls from ethnic minorities should be encouraged to eliminate the inequality in cervical cancer incidence in the medium term. We recommend that dynamic effects should be considered when estimating the effect of public health programmes on equality.

FUNDING

Cancer Research UK.

Impact of HPV vaccination with Gardasil® in Switzerland

BACKGROUND

Gardasil®, a quadrivalent vaccine targeting low-risk (6, 11) and high-risk (16, 18) human papillomaviruses (HPV), has been offered to 11-14 year-old schoolgirls in Switzerland since 2008. To evaluate its success and its potential impact on cervical cancer screening, HPV genotypes were examined in 18-year-old girls five years later (sub-study 1) and in outpatients participating to cervical cancer screening before and after vaccine implementation (sub-study 2).

METHODS

For sub-study 1, 3726 females aged 18 in 2013 were invited to fill a questionnaire on personal demographics and HPV risk factors and to provide a self-collected cervicovaginal sample for HPV genotyping and Chlamydia trachomatis PCR. Personal data were evaluated by univariable and multivariable statistics. In sub-study 2, the proportion of the vaccine-type HPV among anogenital HPV was examined with archived genotyping data of 8039 outpatients participating to cervical cancer screening from 1999 till 2015. The yearly evolution of this proportion was evaluated by segmented logistic regression.

RESULTS

690 (18.5%) women participated to sub-study 1 and 327 (8.8%) provided a self-collected sample. Prevalence of Chlamydia trachomatis (4.6%) and demographics confirmed that the subjects were representative of sexually-active Swiss young women. Vaccine (five-year coverage: 77.5%) was preferentially accepted by contraceptive-pill users (P = 0.001) and samples were mainly provided by sexually-active subjects (P < 0.001). The proportion (4%) of the vaccine-type HPV in this population was lower than in sub-study 2 outpatients (n = 849, <26 years old) in the pre-vaccine era (25.7%). The proportion of the high-risk vaccine-type HPV decreased significantly (59%, P = 0.0048) in the outpatients during the post-vaccine era, yet this decrease was restricted to those aged less than 26 years (n = 673, P < 0.0001).

CONCLUSIONS

The low proportion of vaccine-type HPV in 18-year-old females and its rapid decrease in young women participating to cervical cancer screening extend the success of HPV vaccination to Switzerland. Our data suggest that cervical cancer screening is now entering a stage of reduced proportion of HPV16 and/or 18 in samples reported positive by cytology. In view of the high likelihood of reduced clinical specificity of cytology, primary screening modalities involving HPV testing and cytology should now be re-evaluated in Switzerland.

The early impact of human papillomavirus vaccination on anogenital warts in Québec, Canada

In Québec province in Canada, a public school-based and catch-up HPV vaccination programs with the quadrivalent vaccine have been introduced in September 2008 for girls aged 9-17 years. We assessed the early impact of the HPV vaccination program on the incidence of anogenital warts (AGW) in the Quebec general population. We used the provincial health administrative data of the Régie de l'assurance maladie du Québec (RAMQ). AGW were identified either through a prescription of podofilox, or a medical procedure code specific to AGW, or a diagnostic code for viral warts followed by a prescription of imiquimod or fluorouracil. Sex- and age-specific incidence rates were calculated for pre-vaccination (2004-2007) and vaccination (2009-2012) periods. We found a significant decline of 45% and 19% in the incidence of AGWs among females aged 15-19 and 20-24 years, respectively. A decline of 21% was also seen among males aged 15-19 years. The median age at an episode of AGW increased from 27 years in 2004 to 31 years in 2012 among females and remained stable in males. Our findings indicate that the HPV public vaccination program is associated with an important reduction in the incidence of AGW among young females and males. The benefit is more pronounced among females 15-19 years of age, who were eligible for the public vaccination program. The observed decline among young males could be due to herd immunity and/or privately paid vaccination.

Human Papillomavirus and Its Testing Assays, Cervical Cancer Screening, and Vaccination

Human papillomavirus (HPV) was found to be the causative agent for cervical cancer in the 1980s with almost 100% of cervical cancer cases testing positive for HPV. Since then, many studies have been conducted to elucidate the molecular basis of HPV, the mechanisms of carcinogenesis of the virus, and the risk factors for HPV infection. Traditionally, the Papanicolaou test was the primary screening method for cervical cancer. Because of the discovery and evolving understanding of the role of HPV in cervical dysplasia, HPV testing has been recommended as a new method for cervical cancer screening by major professional organizations including the American Cancer Society, American Society for Colposcopy and Cervical Pathology, and the American Society for Clinical Pathology. In order to detect HPV infections, many sensitive and specific HPV assays have been developed and used clinically. Different HPV assays with various principles have shown their unique advantages and limitations. In response to a clear causative relationship between high-risk HPV and cervical cancer, HPV vaccines have been developed which utilize virus-like particles to create an antibody response for the prevention of HPV infection. The vaccines have been shown in long-term follow-up studies to be effective for up to 8 years; however, how this may impact screening for vaccinated women remains uncertain. In this chapter, we will review the molecular basis of HPV, its pathogenesis, and the epidemiology of HPV infection and associated cervical cancer, discuss the methods of currently available HPV testing assays as well as recent guidelines for HPV screening, and introduce HPV vaccines as well as their impact on cervical cancer screening and treatments.

Determinants of geographic inequalities in HPV vaccination in the most populated region of France

BACKGROUND

In France, there are recommendations and reimbursements for human papillomavirus (HPV) vaccination but no HPV vaccination programs. Therefore, vaccination is largely determined by parents' initiative, which can lead to inequalities. The objective of this study was to determine the factors associated with poorer vaccination coverage rates in the most populated region of France.

METHODS

The data of this study were obtained from the National Health Insurance between 2011 and 2013. Correlations between vaccination initiation rate (at least 1 dose reimbursed) and socio-demographic/cultural factors were assessed using Pearson's product-moment correlation coefficient. Multivariate analyses were performed using logistic regression.

RESULTS

In total, 121,636 girls received at least one HPV vaccine dose. The vaccination rate for girls born from 1996 to 1999 was 18.7%. Disparities in vaccination coverage rates were observed between the 8 departments of the region, ranging from 12.9% to 22.6%. At the department level, unemployment, proportion of immigrants and foreigners, and coverage by CMU health insurance ("Couverture Maladie Universelle", a health insurance plan for those who are not otherwise covered through business or employment and who have a low income) were significantly inversely correlated with vaccination rates, whereas urban residence, medical density, income and use of medical services were not related to coverage. In the multivariate model, only the percentage of foreigners remained independently associated with lower vaccination coverage. At the individual level, the use of medical services was a strong driver of HPV vaccination initiation.

CONCLUSION

We observed geographic disparities in HPV vaccination initiation coverage. Even if no clear factor was identified as a vaccination determinant, we observed a failure of vaccination only based on parents' initiative. Therefore, an organized policy on HPV vaccination, such as school-based programs, can help improve coverage rates.

Perceptions of HPV and attitudes towards HPV vaccination amongst men who have sex with men: A qualitative analysis

OBJECTIVES

Men who have sex with men (MSM) are at risk of genital warts and anal cancer due to human papillomavirus (HPV) infection. This study explores MSMs' perceptions of HPV and HPV vaccination prior to the introduction of this programme.

DESIGN

Focus groups and one-to-one interviews with self-identified MSM were conducted between November 2014 and March 2015 in Brighton, UK.

METHODS

Participants were recruited from community-based lesbian-gay-bisexual-transgender (LGBT) venues and organizations. Discussions were recorded, transcribed verbatim, and analysed using framework analysis.

RESULTS

Thirty-three men took part (median age 25 years, IQR: 21-27), most of whom (n = 25) did not know about HPV, anal cancer (31), or HPV vaccination (26). While genital warts and anal cancer were perceived as severe, men did not perceive themselves at risk of HPV. All MSM would accept the HPV vaccine if offered by a health care professional. The challenges of accessing sexual health services or openly discussing same-sex experiences with health care professionals were perceived as barriers to accessing HPV vaccination. Two participants were concerned that selective HPV vaccination could increase stigma and prejudice against MSM, comparable to the AIDS epidemic. Ten MSM were unsure about the effectiveness of HPV vaccination for sexually active men and were in favour of vaccinating all adolescent boys at school.

CONCLUSIONS

Most MSM have poor knowledge about HPV and associated anal cancer. Despite the lack of concern about HPV, most MSM expressed willingness to receive HPV vaccination. There is a need for health education about the risks of HPV and HPV-related diseases so that MSM can appraise the benefits of being vaccinated. Concerns about HPV vaccine effectiveness in sexually active men and possible stigmatization need to be addressed to optimize HPV vaccine acceptability. Statement of contribution What is already known on this subject? Men who have sex with men (MSM) have poor knowledge about HPV and HPV-related diseases. Perceived risk of HPV and attitudes towards HPV vaccination are associated with HPV vaccine acceptability amongst MSM in the United States. There is a gap between acceptability and uptake of HPV vaccination amongst MSM. What does this study add? Due to concerns about compromised effectiveness of the HPV vaccine in sexually active men, most MSM would recommend vaccination of all adolescent boys. Restricted access to sexual health services and the inability to discuss same-sex experiences were perceived as barriers to HPV vaccination. While the HPV vaccine is acceptable amongst MSM, the motivation to be vaccinated and complete the three-dose series might be low.

Evaluation of Type Replacement Following HPV16/18 Vaccination: Pooled Analysis of Two Randomized Trials

Background

Current HPV vaccines do not protect against all oncogenic HPV types. Following vaccination, type replacement may occur, especially if different HPV types competitively interact during natural infection. Because of their common route of transmission, it is difficult to assess type interactions in observational studies. Our aim was to evaluate type replacement in the setting of HPV vaccine randomized controlled trials (RCTs).

Methods

Data were pooled from the Costa Rica Vaccine Trial (CVT; NCT00128661) and PATRICIA trial (NCT001226810)-two large-scale, double-blind RCTs of the HPV-16/18 AS04-adjuvanted vaccine-to compare cumulative incidence of nonprotected HPV infections across trial arms after four years. Negative rate difference estimates (rate in control minus vaccine arm) were interpreted as evidence of replacement if the associated 95% confidence interval excluded zero. All statistical tests were two-sided.

Results

After applying relevant exclusion criteria, 21 596 women were included in our analysis (HPV arm = 10 750; control arm = 10 846). Incidence rates (per 1000 infection-years) were lower in the HPV arm than in the control arm for grouped nonprotected oncogenic types (rate difference = 1.6, 95% confidence interval [CI] = 0.9 to 2.3) and oncogenic/nononcogenic types (rate difference = 0.2, 95% CI = -0.3 to 0.7). Focusing on individual HPV types separately, no deleterious effect was observed. In contrast, a statistically significant protective effect (positive rate difference and 95% CI excluded zero) was observed against oncogenic HPV types 35, 52, 58, and 68/73, as well as nononcogenic types 6 and 70.

Conclusion

HPV type replacement does not occur among vaccinated individuals within four years and is unlikely to occur in vaccinated populations.

Human papillomavirus (HPV)-16/18 AS04-adjuvanted vaccine for the prevention of cervical cancer and HPV-related diseases

Vaccines are available against human papillomavirus (HPV), the causal agent of cervical and other cancers. Efficacy data from the HPV-16/18 AS04-adjuvanted vaccine clinical trial program were reviewed. Six randomized, controlled phase II/III trials evaluating cervical endpoints enrolled women from diverse populations and geographical locations. The program analyzed extensively the cohorts most relevant from a public health perspective: the total vaccinated cohort (TVC), approximating a general population including those with existing or previous HPV infection, and TVC-naïve, approximating a population of young women before sexual debut. Results show that the vaccine reduces HPV-16/18 infection and associated cervical endpoints in women regardless of age, location, or sexual experience. It provides cross-protection against some non-vaccine oncogenic HPV types and types causing genital warts, and may be effective against vulvar, oral, and anal HPV infection. Early epidemiology data following its introduction suggest a decline in the prevalence of vaccine and some non-vaccine HPV types.

Systematic Review and Meta-Analysis of Interventions to Improve Access and Coverage of Adolescent Immunizations

Vaccination strategies are among the most successful and cost-effective public health strategies for preventing disease and death. Until recently, most of the existing immunization programs targeted infants and children younger than 5 years which have successfully resulted in reducing global infant and child mortality. Adolescent immunization has been relatively neglected, leaving a quarter of world's population underimmunized and hence vulnerable to a number of preventable diseases. In recent years, a large number of programs have been launched to increase the uptake of different vaccines in adolescents; however, the recommended vaccination coverage among the adolescent population overall remains very low, especially in low- and middle-income countries. Adolescent vaccination has received significantly more attention since the advent of the human papillomavirus (HPV) vaccine in 2006. However, only half of the adolescent girls in the United States received a single dose of HPV vaccine while merely 43% and 33% received two and three doses, respectively. We systematically reviewed literature published up to December 2014 and included 23 studies on the effectiveness of interventions to improve immunization coverage among adolescents. Moderate-quality evidence suggested an overall increase in vaccination coverage by 78% (relative risk: 1.78; 95% confidence interval: 1.41-2.23). Review findings suggest that interventions including implementing vaccination requirement in school, sending reminders, and national permissive recommendation for adolescent vaccination have the potential to improve immunization uptake. Strategies to improve coverage for HPV vaccines resulted in a significant decrease in the prevalence of HPV by 44% and genital warts by 33%; however, the quality of evidence was low. Analysis from single studies with low- or very low-quality evidence suggested significant decrease in varicella deaths, measles incidence, rubella susceptibility, and incidence of pertussis while the impact was nonsignificant for incidence of mumps with their respective vaccines. Further rigorous evidence is needed to evaluate the effectiveness of strategies to improve immunization uptake among adolescents from low- and middle-income countries.

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

BACKGROUND

 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.

METHODS

 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.

RESULTS

 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).

CONCLUSIONS

 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.

Human Papillomavirus Prevalence and Herd Immunity after Introduction of Vaccination Program, Scotland, 2009-2013

Prevalence was reduced, and early evidence indicates herd immunity.

In 2008, a national human papillomavirus (HPV) immunization program using a bivalent vaccine against HPV types 16 and 18 was implemented in Scotland along with a national surveillance program designed to determine the longitudinal effects of vaccination on HPV infection at the population level. Each year during 2009–2013, the surveillance program conducted HPV testing on a proportion of liquid-based cytology samples from women undergoing their first cervical screening test for precancerous cervical disease. By linking vaccination, cervical screening, and HPV testing data, over the study period we found a decline in HPV types 16 and 18, significant decreases in HPV types 31, 33, and 45 (suggesting cross-protection), and a nonsignificant increase in HPV 51. In addition, among nonvaccinated women, HPV types 16 and 18 infections were significantly lower in 2013 than in 2009. Our results preliminarily indicate herd immunity and sustained effectiveness of the bivalent vaccine on virologic outcomes at the population level.

Significantly Reduced Genoprevalence of Vaccine-Type HPV-16/18 Infections among Vaccinated Compared to Non-Vaccinated Young Women 5.5 Years after a Bivalent HPV-16/18 Vaccine (Cervarix®) Pilot Project in Uganda

The objective of this study was to determine the prevalence and some predictors for vaccine and non-vaccine types of HPV infections among bivalent HPV vaccinated and non-vaccinated young women in Uganda. This was a comparative cross sectional study 5.5 years after a bivalent HPV 16/18 vaccination (Cervarix®, GlaxoSmithKline, Belgium) pilot project in western Uganda. Cervical swabs were collected between July 2014-August 2014 and analyzed with a HPV genotyping test, CLART^® HPV2 assay (Genomica, Madrid Spain) which is based on PCR followed by microarray for determination of genotype. Blood samples were also tested for HIV and syphilis infections as well as CD4 and CD8 lymphocyte levels. The age range of the participants was 15–24 years and mean age was 18.6(SD 1.4). Vaccine-type HPV-16/18 strains were significantly less prevalent among vaccinated women compared to non-vaccinated women (0.5% vs 5.6%, p 0.006, OR 95% CI 0.08(0.01–0.64). At type-specific level, significant difference was observed for HPV16 only. Other STIs (HIV/syphilis) were important risk factors for HPV infections including both vaccine types and non-vaccine types. In addition, for non-vaccine HPV types, living in an urban area, having a low BMI, low CD4 count and having had a high number of life time sexual partners were also significant risk factors. Our data concurs with the existing literature from other parts of the world regarding the effectiveness of bivalent HPV-16/18 vaccine in reducing the prevalence of HPV infections particularly vaccine HPV- 16/18 strains among vaccinated women. This study reinforces the recommendation to vaccinate young girls before sexual debut and integrate other STI particularly HIV and syphilis interventions into HPV vaccination packages.

Human papillomavirus molecular biology

Human papillomaviruses are small DNA viruses with a tropism for squamous epithelia. A unique aspect of human papillomavirus molecular biology involves dependence on the differentiation status of the host epithelial cell to complete the viral lifecycle. A small group of these viruses are the etiologic agents of several types of human cancers, including oral and anogenital tract carcinomas. This review focuses on the basic molecular biology of human papillomaviruses.

Impact of 2-, 4- and 9-valent HPV vaccines on morbidity and mortality from cervical cancer

Cervical cancer causes significant morbidity and mortality worldwide. Most cervical cancers are associated with oncogenic human papillomavirus (HPV), and vaccination with any of 3 available HPV vaccines is anticipated to greatly reduce the burden of cervical cancer. This review provides an overview of the burden of HPV, the efficacy and clinical effectiveness of the bivalent (HPV 16, 18), quadrivalent (HPV 6, 11, 16, 18) and 9vHPV (HPV 6, 11, 16, 1831, 33, 45, 52, 58) vaccines in order to assess the anticipated impact on cervical cancer. All three vaccines show high efficacy in prevention of vaccine-specific HPV-type infection and associated high-grade cervical dysplasia in HPV-naïve women. Early clinical effectiveness data for the bivalent and quadrivalent vaccine demonstrate reduced rates of HPV 16 and 18 prevalence in vaccinated cohorts; data evaluating cervical dysplasia and cervical procedures as outcomes will shed further light on the clinical effectiveness of both vaccines. The bivalent vaccine has demonstrated cross-protection to non-vaccine HPV types, including the types in the 9vHPV vaccine. No clinical effectiveness data is yet available for the 9vHPV vaccine.  While HPV vaccination has great promise to reduce cervical cancer morbidity and mortality, estimated benefits are largely theoretical at present. Large population-based clinical effectiveness studies will provide long-term immunogenicity and effectiveness, as well as assessment of cervical cancer as an endpoint, particularly as young vaccinated women enter the appropriate age range to initiate screening for cervical cancer. Strengthening screening and treatment programs will likely have the greatest impact in the short-term on cervical cancer morbidity and mortality.

Estimating the cost-effectiveness profile of a universal vaccination programme with a nine-valent HPV vaccine in Austria

BACKGROUND

HPV is a major cancer-causing factor in both sexes in the cervix, vulva, vagina, anus, penis, oropharynx as well as the causal factor in other diseases such as genital warts and recurrent respiratory papillomatis. In the context of the arrival of a nonavalent HPV vaccine (6/11/16/18/31/33/45/52/58), this analysis aims to estimate the public health impact and the incremental cost-effectiveness of a universal (girls and boys) vaccination program with a nonavalent HPV vaccine as compared to the current universal vaccination program with a quadrivalent HPV vaccine (6/11/16/18), in Austria.

METHOD

A dynamic transmission model including a wide range of health and cost outcomes related to cervical, anal, vulvar, vaginal diseases and genital warts was calibrated to Austrian epidemiological data. The clinical impact due to the 5 new types was included for cervical and anal diseases outcomes only. In the base case, a two-dose schedule, lifelong vaccine type-specific protection and a vaccination coverage rate of 60% and 40% for girls and boys respectively for the 9-year old cohorts were assumed. A cost-effectiveness threshold of €30,000/QALY-gained was considered.

RESULTS

Universal vaccination with the nonavalent vaccine was shown to reduce the incidence of HPV16/18/31/33/45/52/58 -related cervical cancer by 92%, the related CIN2/3 cases by 96% and anal cancer by 83% and 76% respectively in females and males after 100 years, relative to 75%, 76%, 80% and 74% with the quadrivalent vaccine, respectively. Furthermore, the nonavalent vaccine was projected to prevent an additional 14,893 cases of CIN2/3 and 2544 cases of cervical cancer, over 100 years. Depending on the vaccine price, the strategy was shown to be from cost-saving to cost-effective.

CONCLUSION

The present evaluation showed that vaccinating 60% of girls and 40% of boys aged 9 in Austria with a 9-valent vaccine will substantially reduce the incidence of cervical cancer, CIN and anal cancer compared to the existing strategy. The vaccination strategies performed with the 9-valent vaccine in the current study were all found to be cost-effective compared to the current quadrivalent vaccination strategy by considering a cost-effectiveness threshold of 30,000€/QALY gained.

Vaccine Misconceptions and Low HPV Vaccination Take-up Rates in Singapore

BACKGROUND

HPV vaccination in Singapore is voluntary and physician prescription-based. This study investigated the current status and intention for HPV vaccination among Singapore nurses.

MATERIALS AND METHODS

All female nurses in a general hospital were given an anonymous questionnaire on HPV vaccination experience and intention of vaccinating their daughters. The influence of age, knowledge and perceived-risk of cervical cancer, and cultural background on mother's intention of vaccinating their daughters was analyzed.

RESULTS

Of 2,000 nurses, 1,622 (81.1%) responded and analysis was performed on 1,611 with valid data. They showed good awareness on association of cervical cancer with multiple sexual partners (81.9%), history of sexually transmissible diseases (78.2%), and history of genital warts/HPV infection (73.5%), and on cervical cancer preventive effects of HPV vaccination (54.6%). The prevailing misconceptions of the vaccines were: investigational nature (38.9%), side effects (27.9%) and indicated for women at high risk for cervical cancer (20.5%).

CONCLUSIONS

Misconceptions on the nature, role and safety of HPV vaccines low vaccine up-take rates and daughters. Dissemination of adequate and accurate HPV vaccine information and a review for school-based vaccination are needed for optimal delivery of HPV vaccines in Singapore.

Cervical cancer screening: evidence behind the guidelines

Cervical cancer screening involves a complex process of cytology, human papillomavirus (HPV) testing, colposcopy, and a multitude of algorithms for the identification of preinvasive disease and prevention of invasive disease. High-risk HPV is a prerequisite for the development of almost all types of cervical cancer; therefore, a test for high-risk HPV has become an integral part of new screening strategies. Major changes to screening guidelines in the last decade include initiation of screening at age 21 years, conservative management of young women with abnormal cytology, extended screening intervals for women age ≥30 years, and cessation of screening in low-risk women at age 65 years. This review will focus on the evidence that has led to the current evidence-based guidelines. Evidence regarding primary HPV testing as well as postvaccine-based screening strategies will also be reviewed.

Human Papillomavirus Laboratory Testing: the Changing Paradigm

High-risk human papillomaviruses (HPVs) cause essentially all cervical cancers, most anal and oropharyngeal cancers, and some vaginal, vulvar, and penile cancers. Improved understanding of the pathogenesis of infection and the availability of newer tests are changing the approach to screening and diagnosis. Molecular tests to detect DNA from the most common high-risk HPVs are FDA approved for use in conjunction with cytology in cervical cancer screening programs. More-specific tests that detect RNA from high-risk HPV types are now also available. The use of molecular tests as the primary screening tests is being adopted in some areas. Genotyping to identify HPV16 and -18 has a recommended role in triaging patients for colposcopy who are high-risk HPV positive but have normal cytology. There are currently no recommended screening methods for anal, vulvar, vaginal, penile, or oropharyngeal HPV infections. HPV testing has limited utility in patients at high risk for anal cancer, but p16 immunohistochemistry is recommended to clarify lesions in tissue biopsy specimens that show moderate dysplasia or precancer mimics. HPV testing is recommended for oropharyngeal squamous cell tumors as a prognostic indicator. Ongoing research will help to improve the content of future guidelines for screening and diagnostic testing.

Prevalence of HPV After Introduction of the Vaccination Program in the United States

BACKGROUND

Since mid-2006, human papillomavirus (HPV) vaccination has been recommended for females aged 11 to 12 years and through 26 years if not previously vaccinated.

METHODS

HPV DNA prevalence was analyzed in cervicovaginal specimens from females aged 14 to 34 years in NHANES in the prevaccine era (2003-2006) and 4 years of the vaccine era (2009-2012) according to age group. Prevalence of quadrivalent HPV vaccine (4vHPV) types (HPV-6, -11, -16, and -18) and other HPV type categories were compared between eras. Prevalence among sexually active females aged 14 to 24 years was also analyzed according to vaccination history.

RESULTS

Between the prevacccine and vaccine eras, 4vHPV type prevalence declined from 11.5% to 4.3% (adjusted prevalence ratio [aPR]: 0.36 [95% confidence interval (CI): 0.21-0.61]) among females aged 14 to 19 years and from 18.5% to 12.1% (aPR: 0.66 [95% CI: 0.47-0.93]) among females aged 20 to 24 years. There was no decrease in 4vHPV type prevalence in older age groups. Within the vaccine era, among sexually active females aged 14 to 24 years, 4vHPV type prevalence was lower in vaccinated (≥1 dose) compared with unvaccinated females: 2.1% vs 16.9% (aPR: 0.11 [95% CI: 0.05-0.24]). There were no statistically significant changes in other HPV type categories that indicate cross-protection.

CONCLUSIONS

Within 6 years of vaccine introduction, there was a 64% decrease in 4vHPV type prevalence among females aged 14 to 19 years and a 34% decrease among those aged 20 to 24 years. This finding extends previous observations of population impact in the United States and demonstrates the first national evidence of impact among females in their 20s.