No evidence for cross-protection of the HPV-16/18 vaccine against HPV-6/11 positivity in female STI clinic visitors

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.

Genital Warts in Women Vaccinated against HPV in Childhood: A Systematic Review

Human papillomavirus (HPV) is the most prevalent sexually transmitted infection among young women. Notably, more than ten years after the introduction of HPV vaccination programs in Europe, it is essential to review the real-world evidence of the incidence of anogenital warts (GWs) among women vaccinated during childhood. In this systematic review, three databases were searched for studies published between January 2008 and September 2023. Nine cohort studies were included. A total of 890,320 HPV-vaccinated women and 1,922,033 unvaccinated women were evaluated. All the studies but one investigated the 4vHPV vaccine. The incidence rate of GWs in vaccinated women ranged from 0.0 to 1650 per 100,000 person-years. The highest incidence rates were found in women vaccinated with one dose at the age of 17-19 years old and in fully vaccinated women only after 19 years of age. Similar incidence values were reported among unvaccinated women. The incidence of GWs was lower when the age at first dose was 9-11 years old. This systematic review reveals that the incidence of GWs among HPV-vaccinated women is related to the age of vaccination and the number of vaccine doses received. In the post-vaccination era, epidemiological surveillance of the incidence of GWs and their genotypes is crucial.

Effects of 2 and 3 Vaccinations With the Bivalent Human Papillomavirus (HPV) Vaccine on the Prevalence and Load of HPV in Clearing and Persistent Infections in Young Women

BACKGROUND

Human papillomavirus (HPV) viral load (VL) is associated with persistence, which increases cervical cancer risk. The bivalent vaccine protects against oncogenic HPV-16/18 and cross-protects against several nonvaccine types. We examined the effect of 2-dose (2D) and 3-dose (3D) vaccination on HPV prevalence and VL in clearing infections and persistent infections, 6 years and 12 years postvaccination, respectively.

METHODS

Vaginal swabs collected from the "HPV Amongst Vaccinated and Non-vaccinated Adolescents" study (HAVANA, 3D-eligible) and HAVANA-2 (2D-eligble) participants were genotyped for HPV with the SPF10-DEIA-LiPA25 system. HPV VL was measured with type-specific quantitative polymerase chain reaction (qPCR).

RESULTS

HPV-16, -18, -31, -33, and -45 clearing and/or persistent infection prevalence and HPV-16, -18, and -31 VLs in clearing infections were significantly reduced in 3D-vaccinated women compared to unvaccinated women. Except for HPV-11 and -59 clearing infections, no significant VL differences were observed among vaccinated women, ≤6 and >6 years post-vaccination. Infection numbers were low in 2D-eligible women, with no HPV-16/18 in vaccinated women. No VL differences for the remaining types were found.

CONCLUSIONS

3D vaccination reduces HPV prevalence in clearing infections and persistent infections and decreases HPV VLs in clearing infections, 12 years post-vaccination for vaccine and several nonvaccine types. 2D-eligible women had low infection numbers, with no HPV-16/18 among vaccinated women.

A two-sex model of human papillomavirus infection: Vaccination strategies and a case study

Vaccination is effective in preventing human papillomavirus (HPV) infection. It still remains debatable whether males should be included in a vaccination program and unclear how to allocate the vaccine in genders to achieve the maximum benefits. In this paper, we use a two-sex model to assess HPV vaccination strategies and use the data from Guangxi Province in China as a case study. Both mathematical analysis and numerical simulations show that the basic reproduction number, an important indicator of the transmission potential of the infection, achieves its minimum when the priority of vaccination is given to the gender with a smaller recruit rate. Given a fixed amount of vaccine, splitting the vaccine evenly usually leads to a larger basic reproduction number and a higher prevalence of infection. Vaccination becomes less effective in reducing the infection once the vaccine amount exceeds the smaller recruit rate of the two genders. In the case study, we estimate the basic reproduction number is 1.0333 for HPV 16/18 in people aged 15-55. The minimal bivalent HPV vaccine needed for the disease prevalence to be below 0.05% is 24050 per year, which should be given to females. However, with this vaccination strategy it would require a very long time and a large amount of vaccine to achieve the goal. In contrast with allocating the same vaccine amount every year, we find that a variable vaccination strategy with more vaccine given in the beginning followed by less vaccine in later years can save time and total vaccine amount. The variable vaccination strategy illustrated in this study can help to better distribute the vaccine to reduce the HPV prevalence. Although this work is for HPV infection and the case study is for a province in China, the model, analysis and conclusions may be applicable to other sexually transmitted diseases in other regions or countries.

Partial Protective Effect of Bivalent Human Papillomavirus 16/18 Vaccination Against Anogenital Warts in a Large Cohort of Dutch Primary Care Patients

Background

There is ongoing debate about the possible protective effect of the bivalent human papillomavirus (2vHPV) vaccine, targeting oncogenic types HPV-16/18, against anogenital warts (AGWs), commonly attributed to HPV-6/11. We performed a retrospective registry-based open cohort study to assess the effect of 2vHPV vaccination on AGWs.

Methods

We linked general practice (ie, primary care) data from women born between 1993 and 2002, who had been eligible for HPV vaccination in the Netherlands, to the Dutch national immunization registry on an individual level. Women were followed until their first AGW diagnosis or end of follow-up. Adjusted incidence rate ratios (aIRRs) were estimated using Poisson regression with vaccination status as a time-dependent exposure.

Results

We linked data of 96 468 women with a total of 328 019 years observation time and 613 AGW diagnoses (incidence: 1.87/1000 person-years). At the end of follow-up, 61% were 2vHPV vaccinated (≥ 1 dose) of whom 91% were fully vaccinated. The AGW incidence was lower among those with ≥ 1 dose vs 0 doses (aIRR, 0.75 [95% confidence interval {CI}, .64–.88]). The effect of vaccination was stronger after full vaccination (aIRR, 0.72 [95% CI, .61–.86]) and for women who were offered vaccination at 12–13 years of age (aIRR, 0.69 [95% CI, .51–.93]) vs those at 13–16 years of age (aIRR, 0.77 [95% CI, .64–.93]).

Conclusions

This is the largest population-based study so far to examine the effect of 2vHPV vaccination on AGWs, with reliable individual information on AGW diagnoses and vaccination status. The results indicate that 2vHPV vaccination partially protects against AGWs, especially when administered in early adolescence.

Post-vaccination HPV seroprevalence among female sexual health clinic attenders in England

BACKGROUND

The National HPV Immunisation Programme was introduced in England in September 2008 using the HPV16/18 bivalent vaccine. We conducted serological surveillance to explore vaccination coverage levels. We also conducted a case-control study to investigate a hypothesised cross-protective effect of the HPV16/18 vaccine against genital warts.

METHODS

Residual serum specimens from 16 to 20 year-old women attending six specialist sexual health services (SSHS) between 2011 and 2015 in England were tested for antibodies against HPV16 and HPV18 using a virus-like particle (VLP)-based multiplex serology assay. Patients were classified as having vaccine-induced seropositivity if they were seropositive for both HPV types and either had high antibody levels for at least one HPV type, or moderately high levels for both HPV types. Differences in vaccine-induced seropositivity by patient characteristics were investigated using logistic regression. Vaccine-induced seropositivity was then compared for patients with genital warts (cases) and matched patients without (controls).

RESULTS

Of 3,973 serum specimens collected, 3,870 (97.4%) had a valid result. The proportion of women with vaccine-induced seropositivity decreased with age (from 78.1% in 16-year-olds to 52.6% in 20-year-olds). Vaccine-induced seropositivity was lower among women born outside the UK, from more deprived areas and with a history of chlamydia diagnosis. A difference in uptake by ethnic group was also seen but this was largely confounded by differences in deprivation and country of birth. Among 537 cases and 1,515 controls, there was little evidence of a protective effect of the bivalent HPV vaccine against genital warts (adjusted odds ratio 0.93; 95% CI: 0.74-1.18).

DISCUSSION

Vaccine-induced seropositivity in this high-risk population was in line with vaccination coverage in the general population although was lower in some at-risk sub-groups. This study does not provide evidence to support a cross-protective effect of the HPV16/18 vaccine against genital warts.

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.

Bivalent Human Papillomavirus (HPV) Vaccine Effectiveness Correlates With Phylogenetic Distance From HPV Vaccine Types 16 and 18

To substantiate cross-protection reported across AS04-adjuvanted bivalent human papillomavirus (HPV) vaccine (2vHPV) studies, we reevaluated vaccine effectiveness against type-specific HPV positivity as a function of phylogenetic distance to vaccine target types HPV-16 and -18. We provide evidence of sustained cross-protection up to 8 years postvaccination in a high-risk population in the Netherlands. Moreover, our findings suggest that genomic distance better explains cross-protection than distance measures based on capsid antigens only. Taken together, 2vHPV is predicted to provide partial cross-protection against HPV-31, -33, -35, -45, -52, and possibly -58, that is, acknowledged oncogenic types with close phylogenetic relationships to HPV-16 or -18.

The impact of HPV multi-cohort vaccination: Real-world evidence of faster control of HPV-related morbidity

BACKGROUND

In 2009, both Norway and Denmark initiated routine quadrivalent human papillomavirus vaccination (qHPV) for 12-year-old girls; however, Denmark also introduced free-of-charge multi-cohort vaccination for older age groups in 2008. We aim to describe trends in genital warts (GWs) incidence rates (IRs) among men and women and qHPV vaccine coverage among women in Norway and Denmark in 2006-2015.

METHODS

We linked multiple national health registries in Norway and Denmark via national personal identifiers to access data on GWs incidence and qHPV vaccination among women and men aged 12-35 years residing in Norway and Denmark in 2006-2015. We calculated age-specific and age-standardized GWs IRs, GWs IR trends before (2006-2009) and after (2009-2015) the implementation of qHPV vaccination, and qHPV vaccine coverage among women.

RESULTS

In Norway and Denmark together, there were more than 200,000 cases of incident GWs and over 710,000 girls got at least one dose of qHPV vaccine during the study period. The total qHPV coverage in Norway and Denmark in 2015 was among women aged 12-35 years 24% and 70%, respectively. GWs IRs in Norway and Denmark decreased annually in 2009-2015 among women by 4.8% (95% confidence interval: 4.3 to 5.3) and 18.0% (95%CI: 17.5 to 18.6), respectively, and among men 1.9% (95%CI: 1.4 to 2.4) and 10.7% (95%CI: 10.3 to 11.2), respectively. In Denmark, GWs IRs decreased rapidly among both sexes and all age groups after qHPV vaccination, while Norway showed only a modest decrease.

CONCLUSION

Rapid decline in HPV-related morbidity is feasible with high coverage of multi-cohort vaccination. However, the decision to vaccinate a single cohort of 12-years-old girls only will postpone HPV-related disease control by at least a decade. Thus countries planning HPV vaccination programs should also initiate multi-cohort vaccination for faster disease control.

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.

Epidemiology of genital warts in the British population: implications for HPV vaccination programmes

OBJECTIVES

To estimate the prevalence of, and describe risk factors for, genital warts (GWs) in the British population, following the introduction of the bivalent (human papillomavirus (HPV)-16/18) vaccination programme in girls, and prior to the switch to quadrivalent (HPV-6/11/16/18) vaccine (offering direct protection against GWs) and compare this with GW diagnoses in the prevaccination era.

METHODS

Natsal-3, a probability sample survey in Britain, conducted in 2010-2012, interviewed 9902 men and women aged 16-44. Natsal-2, conducted in 1999-2001, surveyed 11 161 men and women aged 16-44. Both surveys collected data on sexual behaviour and sexually transmitted infection diagnoses using computer-assisted interview methods.

RESULTS

In Natsal-3, 3.8% and 4.6% of sexually experienced men and women reported ever having a diagnosis of GWs, with 1.3% of men and 1.7% of woman reporting a GWs diagnosis in the past 5 years. GWs were strongly associated with increasing partner numbers and condomless sex. Diagnoses were more frequent in men who have sex with men (MSM) (11.6% ever, 3.3% past 5 years) and in women reporting sex with women (10.8% ever, 3.6% past 5 years). In the age group who were eligible for vaccination at the time of Natsal-3 (16-20 years), a similar proportion of same-aged women reported a history of GWs in Natsal-2 (1.9%, 1.1-3.4) and Natsal-3 (2.6%, 1.5-4.4).

CONCLUSIONS

These data provide essential parameters for mathematical models that inform cost-effectiveness analyses of HPV vaccination programmes. There was no evidence of population protection against GWs conferred by the bivalent vaccine. Even with vaccination of adolescent boys, vaccination should be offered to MSM attending sexual health clinics.

Bivalent Vaccine Effectiveness Against Type-Specific HPV Positivity: Evidence for Cross-Protection Against Oncogenic Types Among Dutch STI Clinic Visitors

Background

Observational postmarketing studies are important to assess vaccine effectiveness (VE). We estimated VE from the bivalent human papillomavirus (HPV) vaccine against HPV positivity of vaccine and nonvaccine types in a high-risk population.

Methods

We included all vaccine-eligible women from the PASSYON study, a biennial cross-sectional survey in Dutch sexually transmitted infection clinics. Vaginal swabs were analyzed using a polymerase chain reaction-based assay (SPF10-LiPA25) able to detect the 12 high-risk HPV (hrHPV) types 16/18/31/33/35/39/45/51/52/56/58/59. We compared hrHPV positivity between self-reported vaccinated (≥1 dose) and unvaccinated women, and estimated VE by a logistic mixed model.

Results

We included 1087 women of which 53% were hrHPV positive and 60% reported to be vaccinated. The adjusted pooled VE against HPV-16/18 was 89.9% (81.7%-94.4%). Moreover, we calculated significant VE against nonvaccine types HPV-45 (91%), HPV-35 (57%), HPV-31 (50%), and HPV-52 (37%). Among women who were offered vaccination 5/6 years ago, we estimated similar VE against HPV-16/18 (92%) and all hrHPV types (35%) compared to women who were offered vaccination <5 years ago (83% and 33%, respectively).

Conclusion

We demonstrated high VE of the bivalent vaccine against HPV-16/18 and cross-protection against HPV-45/35/31/52. Protection against HPV-16/18 was sustained up to 6 years postvaccination.

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.

Efficacy, immunogenicity, and safety of a 9-valent human papillomavirus vaccine in Latin American girls, boys, and young women

BACKGROUND

A 9-valent human papillomavirus (HPV6/11/16/18/31/33/45/52/58; 9vHPV) vaccine was developed to expand coverage of the previously developed quadrivalent (HPV6/11/16/18; qHPV) vaccine.

METHODS

Efficacy, immunogenicity, and safety outcomes were assessed in Latin American participants enrolled in 2 international studies of the 9vHPV vaccine, including a randomized, double-blinded, controlled with qHPV vaccine, efficacy, immunogenicity, and safety study in young women aged 16-26 years, and an immunogenicity and safety study in girls and boys aged 9-15 years. Participants (N=5312) received vaccination at Day 1, Month 2, and Month 6. Gynecological swabs were collected regularly in young women for cytological and HPV DNA testing. Serum was analyzed for HPV antibodies in all participants. Adverse events (AEs) were also monitored in all participants.

RESULTS

The 9vHPV vaccine prevented HPV 31-, 33-, 45-, 52-, and 58-related high-grade cervical, vulvar, and vaginal dysplasia with 92.3% efficacy (95% confidence interval 54.4, 99.6). Anti-HPV6, 11, 16, and 18 geometric mean titers at Month 7 were similar in the 9vHPV and qHPV vaccination groups. Anti-HPV antibody responses following vaccination were higher among girls and boys than in young women. Most (>99%) 9vHPV vaccine recipients seroconverted for all 9 HPV types at Month 7. Antibody responses to the 9 HPV types persisted over 5 years. The most common AEs were injection-site related, mostly of mild to moderate intensity.

CONCLUSIONS

The 9vHPV vaccine is efficacious, immunogenic, and well tolerated in Latin American young women, girls, and boys. These data support 9vHPV vaccination programs in Latin America, a region with substantial cervical cancer burden.

Proposal for cervical cancer screening in the era of HPV vaccination

Eradication of cervical cancer involves the expansion of human papillomavirus (HPV) vaccine coverage and the development of efficient screening guidelines that take vaccination into account. In Korea, the HPV National Immunization Program was launched in 2016 and is expected to shift the prevalence of HPV genotypes in the country, among other effects. The experiences of another countries that implement national immunization programs should be applied to Korea. If HPV vaccines spread nationwide with broader coverage, after a few decades, cervical intraepithelial lesions or invasive cancer should become a rare disease, leading to a predictable decrease in the positive predictive value of cervical screening cytology. HPV testing is the primary screening tool for cervical cancer and has replaced traditional cytology-based guidelines. The current screening strategy in Korea does not differentiate women who have received complete vaccination from those who are unvaccinated. However, in the post-vaccination era, newly revised policies will be needed. We also discuss on how to increase the vaccination rate in adolescence.

9-Valent human papillomavirus vaccine: a review of the clinical development program

INTRODUCTION

The 9-valent human papillomavirus (9vHPV) vaccine covers the same HPV types (6/11/16/18) as the quadrivalent HPV (qHPV) vaccine and 5 additional cancer-causing types (31/33/45/52/58). Epidemiological studies indicate that the 9vHPV vaccine could prevent approximately 90% of cervical cancers, 70-85% of high-grade cervical dysplasia (precancers), 85-95% of HPV-related vulvar, vaginal, and anal cancers, and 90% of genital warts. Areas covered: Study design features and key findings from the 9vHPV vaccine clinical development program are reviewed. In particular, 9vHPV vaccine efficacy was established in a Phase III study in young women age 16-26 years. Efficacy results in young women were extrapolated to pre- and young adolescent girls and boys and young men by immunological bridging (i.e., demonstration of non-inferior immunogenicity in these groups versus young women). Expert commentary: The development of the 9vHPV vaccine is the outcome of 20 years of continuous clinical research. Broad vaccination programs could help substantially decrease the incidence of HPV-related disease.

Current status and future prospects for human papillomavirus vaccines

Cervical cancer is the fourth most frequent cancer among women worldwide. Human papillomaviruses (HPVs) cause almost all cervical cancers in low-income countries. Three prophylactic HPV virus-like particle-based vaccines have been licensed to date, and they have all shown high efficacy and reliable safety profiles. However, isolated safety issues have resulted in a reluctance to use these vaccinations. In addition, the high prices of the vaccinations have caused the inequitable distribution of the vaccine: the prices are unaffordable for low-income countries. Meanwhile, great effort has been put into the development of therapeutic HPV vaccines, including protein/peptide-, live vector-, DNA- and cell-based vaccines. These new vaccines have considerable therapeutic potential but limited practical use. The development of immune checkpoint inhibitors and personalized immunotherapy remain challenges for future study. In this article, the current status of the licensed vaccines, therapeutic HPV vaccines and biosimilars, and new platforms for HPV vaccines, are reviewed, and safety issues related to the licensed vaccines are discussed. In addition, the prospects for HPV vaccines are considered.

Cervical cancer screening in the era of HPV vaccination: A review of shifting paradigms in cytopathology

Significant changes in cervical cancer screening practice, guidelines, and prevention of cervical cancer have taken place in recent years including the raising of initial cervical cancer screening age, changes in frequency of cytology screening, and the adoption of high risk HPV and cytology co-testing for some patients; the introduction of the bivalent, quadrivalent, and 9-valent HPV vaccines; and the recent approval of high risk HPV testing as primary screening with the use of cytology as triage in positive cases. This review discusses the significance of primary HPV screening, the impact of HPV vaccination in the prevalence of cervical cancer and its precursors, the interplay between high risk HPV testing and vaccination, and the implications for clinical and cytological management. Future strategies for cervical screening in the post-vaccination era are also discussed.