Public health impact and cost-effectiveness of a nine-valent gender-neutral HPV vaccination program in France

OBJECTIVES

In France, 9-valent HPV vaccination is recommended routinely for 11-14-years-old girls and as catch-up for 15-19-years-old girls. Recently, recommendation for gender-neutral vaccination (GNV) has been approved. The objectives of the study were to assess the public health impact and cost-effectiveness of a 9-valent GNV compared with girls-only vaccination program (GOV).

METHODS

A published HPV disease transmission dynamic model accounting for herd protection effects with a 100-year time horizon was adapted and calibrated to French data. Epidemiological and economic outcomes included disease cases averted and quality-adjusted life years (QALY). Costs and incremental cost-effectiveness ratio (ICER) were measured in 2018 Euros (€). A coverage rate of 26.2% among girls and boys was assumed for the GNV program based on the current female coverage rate in France. The base case included genital warts, cervical, vulvar, vaginal, and anal cancers. Scenario analyses included all HPV-related diseases and considered higher vaccination coverage rate (60%). Deterministic sensitivity analyses on key inputs were performed.

RESULTS

Over 100 years, GNV resulted in an additional reduction of 9,519 and 3,037 cervical cancer cases and deaths; 6,901 and 1,166 additional anal cancer cases and deaths; and a reduction of additional 1,284,077 genital warts compared with current GOV and an ICER of 24,763€/QALY. When including all HPV-related diseases, the ICER was 15,184€/QALY. At a higher coverage rate (60%), GNV would prevent 17,430 and 4,334 additional anogenital cancer cases and deaths and over two million genital warts compared with GOV with an ICER of 40,401€/QALY. Results were sensitive to a higher discount rate (6% versus 4%) and a shorter duration of protection (20 years versus lifetime).

CONCLUSIONS

In France, GNV has a significant impact in terms of public health benefits and may be considered cost-effective compared with GOV at low and high coverage rates.

Present challenges in cervical cancer prevention: Answers from cost-effectiveness analyses

Simulation models are commonly used to address important health policy issues that cannot be explored through experimental studies. These models are especially useful to determine a set of strategies that result in a good value for money (cost-effectiveness). Several mathematical models simulating the natural history of HPV and related diseases, especially cervical cancer, have been developed to calculate a relative effectiveness and cost-effectiveness of HPV vaccination and cervical cancer screening interventions. Virtually all cost-effectiveness analyses identify HPV vaccination programmes for preadolescent girls to be cost-effective, even for relatively low vaccination coverage rates. Routine vaccination of preadolescent girls is the primary target population for HPV vaccination as it shows to provide the greatest health impact. Cost-effectiveness analyses assessing other vaccine target groups are less conclusive. Adding additional age-cohorts would accelerate health benefits in some years, although cost-effectiveness becomes less favourable as age at vaccination increases. Including men in HPV vaccination programmes may be a less efficient strategy if done at the expense of female vaccination coverage for reducing the burden of HPV in the population. However, as the HPV vaccine price decreases, the cost-effectiveness of universal vaccination improves, becoming equally as efficient as female-only vaccination. Vaccine price is a decisive factor in the cost-effectiveness analyses. The lower the price, the greater the likelihood that vaccination groups other than the primary target would be considered cost-effective.

Human papillomavirus vaccination and the role of herd effects in future cancer control planning: a review

INTRODUCTION

Vaccine herd effects are the indirect protection that vaccinated persons provide to those who remain susceptible to infection, due to the reduced transmission of infections. Herd effects have been an important part of the discourse on how to best implement human papillomavirus (HPV) vaccines and prevent HPV-related diseases.

AREAS COVERED

In this paper, we review the theory of HPV vaccine herd effects derived from mathematical models, give an account of observed HPV vaccine herd effects worldwide, and examine the implications of vaccine herd effects for future cervical cancer screening efforts.

EXPERT COMMENTARY

HPV vaccine herd effects improve the cost-effectiveness of vaccinating preadolescent girls, but contribute to making gender-neutral vaccination less economically efficient. Vaccination coverage and sexual mixing patterns by age are strong determinants of herd effects. Many countries worldwide are starting to observe reductions in HPV-related outcomes likely attributable to herd effects, most notably declining anogenital warts in young men, and declining HPV-16/18 infection prevalence in young unvaccinated women. Policy makers making recommendations for cervical cancer screening will have to consider HPV vaccination coverage and herd effects, as these will affect the positive predictive value of screening and the risk of cervical cancer in unvaccinated women.

Systematic review of cost-effectiveness studies of human papillomavirus (HPV) vaccination: 9-Valent vaccine, gender-neutral and multiple age cohort vaccination

BACKGROUND

The success of human papillomavirus (HPV) national immunization program depends on effective strategies in optimizing the uptake of HPV vaccine. Given the increasing number of economic evaluations, this review was conducted to update the economic evidence on HPV vaccination, by focusing on: (i) 9-valent vaccine compared to bi- or quadrivalent vaccine; (ii) gender-neutral vaccination compared to female only vaccination; and (iii) multiple age cohort immunization compared to single age cohort immunization.

METHODS

Searches were performed until June 2016 using 4 databases: PubMed; Embase; Cochrane Library; and LILACS. The combined WHO, Drummond and CHEERS checklist were used to evaluate the quality of included studies.

RESULTS

Thirty-four studies were included in the review and most of them were conducted in high-income countries. The inclusion of adolescent boys in vaccination program was found to be cost-effective if vaccine price and coverage was low. When coverage for female was above 75%, gender-neutral vaccination was less cost-effective than when targeting only girls aged 9-18 years. Current evidence does not show conclusive proof of greater cost-effectiveness of 9-valent vaccine compared to the older HPV vaccines as the price for 9-valent vaccine was still uncertain. Multicohort immunization strategy was cost-effective in the age range 9-14 years but the upper age limit at which vaccination was no longer cost-effective needs to be further investigated. Key influential parameters identified were duration of vaccine protection, vaccine price, coverage, and discounting rates.

CONCLUSIONS

These findings are expected to support policy-makers in making recommendations for HPV immunization programs on either switching to the 9-valent vaccine or inclusion of adolescent boys' vaccination or extending the age of vaccination.

Cost-effectiveness analysis of the nine-valent HPV vaccine in Italy

Background

In Italy HPV vaccination with the quadrivalent vaccine (Gardasil^®) is offered actively and free of charge to girls aged 12 since 2007. A nine-valent vaccine (Gardasil 9^®) received the European market authorization in 2015 to protect, with only 2 doses, against around 90% of all HPV positive cancers, over 80% of high-grade precancerous lesions and 90% of genital warts caused by HPV types 6/11.

Methods

A dynamic transmission model simulating the natural history of HPV-infections was calibrated to the Italian setting and used to estimate costs and QALYs associated with vaccination strategies. The analyses compared two strategies with the nine-valent vaccine (cervical cancer screening and vaccination in girls only or vaccination in boys and girls) to four alternative strategies (cervical cancer screening and vaccination with quadrialent vaccine in girls only, in both boys and girls, with bivalent vaccine in girls and screening strategy only). The National Health Service perspective was considered.

Conclusion

The switch to the nine-valent vaccine in Italy can further reduce the burden associated to cervical cancer and HPV-related diseases and is highly cost-effective.

Results

Compared to the current vaccination program with quadrivalent vaccine, the nine-valent vaccine in a programme including girls and boys shows further reductions of 17% in the incidence of cervical cancer, 35 and 14% in anal cancer for males and females, as well as over a million cases of genital warts avoided after 100 years. The new technology is associated with an ICER of 10,463€ per QALY gained in universal vaccination, decreasing to 4483€ when considering the vaccine switch for girls-only.

Electronic supplementary material

The online version of this article (doi:10.1186/s12962-017-0073-8) contains supplementary material, which is available to authorized users.

HPV-FASTER: broadening the scope for prevention of HPV-related cancer

Human papillomavirus (HPV)-related screening technologies and HPV vaccination offer enormous potential for cancer prevention, notably prevention of cervical cancer. The effectiveness of these approaches is, however, suboptimal owing to limited implementation of screening programmes and restricted indications for HPV vaccination. Trials of HPV vaccination in women aged up to 55 years have shown almost 90% protection from cervical precancer caused by HPV16/18 among HPV16/18-DNA-negative women. We propose extending routine vaccination programmes to women of up to 30 years of age (and to the 45-50-year age groups in some settings), paired with at least one HPV-screening test at age 30 years or older. Expanding the indications for HPV vaccination and much greater use of HPV testing in screening programmes has the potential to accelerate the decline in cervical cancer incidence. Such a combined protocol would represent an attractive approach for many health-care systems, in particular, countries in Central and Eastern Europe, Latin America, Asia, and some more-developed parts of Africa. The role of vaccination in women aged >30 years and the optimal number of HPV-screening tests required in vaccinated women remain important research issues. Cost-effectiveness models will help determine the optimal combination of HPV vaccination and screening in public health programmes, and to estimate the effects of such approaches in different populations.

Public health value of universal HPV vaccination

BACKGROUND

The story of Human Papillomavirus vaccination demands reflection not only for its public health impact on the prophylactic management of HPV disease, but also for its relevant economic and social outcomes. Greater than ever data confirm the efficacy and support the urge for effective vaccination plans for both genders before sexual debut.

METHODS

A review of previous experience in gender-restricted vaccination programs has demonstrated a lower effectiveness. Limiting vaccination to women might increase the psychological burden on women by confirming a perceived inequality between genders; and even if all women were immunized, the HPV chain of transmission would still be maintained through men.

RESULTS

The cost-effectiveness of including boys into HPV vaccination programs should be re-assessed in view of the progressive drop of the economic burden of HPV-related diseases in men and women due to universal vaccination. The cost of the remarkable increase in anal and oropharyngeal HPV driven cancers in both sexes has been grossly underestimated or ignored.

CONCLUSIONS

Steps must be taken by relevant bodies to achieve the target of universal vaccination. The analysis of HPV vaccination's clinical effectiveness vs. economic efficacy are supportive of the economic sustainability of vaccination programs both in women and men. In Europe, these achievements demand urgent attention to the social equity for both genders in healthcare. There is sufficient ethical, scientific, strategic and economic evidence to urge the European Community to develop and implement a coordinated and comprehensive strategy aimed at both genders and geographically balanced, to eradicate cervical cancer and other diseases caused by HPV in Europe. Policymakers must take into consideration effective vaccination programs in the prevention of cancers.

Quadrivalent human papillomavirus (types 6, 11, 16, 18) recombinant vaccine (gardasil(®)): a review of its use in the prevention of premalignant anogenital lesions, cervical and anal cancers, and genital warts

Quadrivalent human papillomavirus (HPV) [types 6, 11, 16, 18] recombinant vaccine (Gardasil(®); Silgard(®)) is composed of virus-like particles formed by self-assembly of recombinant L1 capsid protein from each of HPV types 6, 11, 16 and 18. It is indicated for use from the age of 9 years as a two- or three-dose vaccination course over 6 months for the prevention of premalignant anogenital lesions, cervical and anal cancers, and genital warts caused by the vaccine HPV types. In placebo-controlled trials, quadrivalent HPV vaccine provided high-level protection against infection or disease caused by the vaccine HPV types over 2-4 years in females aged 15-45 years who were negative for the vaccine HPV types, and provided a degree of cross-protection against certain non-vaccine HPV types. The vaccine also provided high-level protection against persistent infection, anogenital precancerous lesions and genital warts caused by the vaccine HPV types over 3 years in susceptible males aged 16-26 years. Protection has been demonstrated for up to 8 years. In subjects who were negative for the vaccine HPV types, high seroconversion rates and high levels of anti-HPV antibodies were observed in females of all age ranges from 9 to 45 years and in males aged 9-26 years. The vaccine was generally well tolerated and was usually predicted to be cost effective in girls and young women. Therefore, quadrivalent HPV vaccine offers an effective means to substantially reduce the burden of HPV-related anogenital disease in females and males, particularly cervical cancer and genital warts.

Development of a quality framework for models of cervical screening and its application to evaluations of the cost-effectiveness of HPV vaccination in developed countries

BACKGROUND

HPV vaccination has now been introduced in most developed countries, but this has occurred in the context of established cervical cancer screening mechanisms which provide population-level protection against the most common HPV-related cancer. Therefore, estimating the cost-effectiveness of HPV vaccination to further reduce HPV-related disease depends in large part on the estimation of the effectiveness of the cervical screening 'background'. The aim of this study was to systematically review and assess methods for simulating cervical screening in decision analytic models used for evaluation of HPV vaccination.

METHODS

Existing quality frameworks for economic models were extended to develop a specific quality framework for models of cervical screening. This involved domains for model structure, parameterisation (data sources) and validation (consistency). A systematic review of economic evaluations of HPV vaccination was then conducted, and assessment of cervical screening model components was then performed via application of the new quality framework.

RESULTS

Generally, models took into account population-level cervical screening participation, but were inconsistent in their approach to modelling abnormal smear management, diagnostic evaluation and treatment of precancerous disease. There was also considerable variability in the accuracy of modelling clinical pathways and the scope of validation performed for screening-related outcomes, with focus directed towards cervical cancer targets. Only a few models comprehensively validated against observed pre-cancerous abnormalities.

CONCLUSION

Models of HPV vaccination in developed countries can be improved by further attention to the 'background' modelling of secondary protection via cervical screening. The quality framework developed for this review can be used to inform future HPV vaccination evaluations, including evaluations of the cost-effectiveness of male vaccination and next generation HPV vaccines, and to assess models used to evaluate new cervical screening technologies and recommendations.

Categorization of methods used in cost-effectiveness analyses of vaccination programs based on outcomes from dynamic transmission models

The aim of this study is to categorize methods used to estimate the cost-effectiveness of vaccination programs using dynamic transmission models, and assess value to decision-makers. A targeted literature search of PubMed has been carried out for this purpose. A review of 43 articles presenting cost-effectiveness analyses of vaccination programs based on dynamic transmission models identified four methods for the estimation of a cost-effectiveness ratio: cumulative population values over a fixed time horizon; population values for a steady-state year; cohort values from time of program initiation; and cohort values at steady state. Cost-effectiveness estimates are sensitive to the choice of time horizon or number of cohorts included. Estimates at steady state are the most comparable to estimates for other healthcare interventions but do not account for pre-steady-state periods. Population values provide estimates of budget impact. In conclusion, four different methods were identified for converting clinical outcomes from a dynamic transmission model to cost-effectiveness estimates. Sensitivity analyses for time horizon or number of cohorts considered should be routinely performed.

Modeling preventative strategies against human papillomavirus-related disease in developed countries

Over the last 5 years, prophylactic vaccination against human papillomavirus (HPV) in pre-adolescent females has been introduced in most developed countries, supported by modeled evaluations that have almost universally found vaccination of pre-adolescent females to be cost-effective. Studies to date suggest that vaccination of pre-adolescent males may also be cost-effective at a cost per vaccinated individual of ~US$400-500 if vaccination coverage in females cannot be increased above ~50%; but if it is possible, increasing coverage in females appears to be a better return on investment. Comparative evaluation of the quadrivalent (HPV16,18,6,11) and bivalent (HPV16,18) vaccines centers around the potential trade-off between protection against anogenital warts and vaccine-specific levels of cross-protection against infections not targeted by the vaccines. Future evaluations will also need to consider the cost-effectiveness of a next generation nonavalent vaccine designed to protect against ~90% of cervical cancers. The timing of the effect of vaccination on cervical screening programs will be country-specific and will depend on vaccination catch-up age range and coverage and the age at which screening starts. Initial evaluations suggest that if screening remains unchanged, it will be less cost-effective in vaccinated compared to unvaccinated women but, in the context of current vaccines, will remain an important prevention method. Comprehensive evaluation of new approaches to screening will need to consider the population-level effects of vaccination over time. New screening strategies of particular interest include delaying the start age of screening, increasing the screening interval and switching to primary HPV screening. Future evaluations of screening will also need to focus on the effects of disparities in screening and vaccination uptake, the potential effects of vaccination on screening participation, and the effects of imperfect compliance with screening recommendations. This article forms part of a special supplement entitled "Comprehensive Control of HPV Infections and Related Diseases" Vaccine Volume 30, Supplement 5, 2012.

Cost-effectiveness of adding vaccination with the AS04-adjuvanted human papillomavirus 16/18 vaccine to cervical cancer screening in Hungary

BACKGROUND

The cervical cancer screening program implemented in Hungary to date has not been successful. Along with screening, vaccination is an effective intervention to prevent cervical cancer. The aim of this study was to assess the cost-effectiveness of adding vaccination with the human papillomavirus 16/18 vaccine to the current cervical cancer screening program in Hungary.

METHODS

We developed a cohort simulation state-transition Markov model to model the life course of 12-year-old girls. Eighty percent participation in the HPV vaccination program at 12 years of age was assumed. Transitional probabilities were estimated using data from the literature. Local data were used regarding screening participation rates, and the costs were estimated in US $. We applied the purchasing power parity exchange rate of 129 HUF/$ to the cost data. Only direct health care costs were considered. We used a 3.7% discount rate for both the cost and quality-adjusted life years (QALYs). The time horizon was 88 years.

RESULTS

Inclusion of HPV vaccination at age 12 in the cervical cancer prevention program was predicted to be cost-effective. The incremental cost-effectiveness ratio (ICER) of adding HPV vaccination to the current national cancer screening program was estimated to be 27 588 $/QALY. The results were sensitive to the price of the vaccine, the discount rate, the screening participation rate and whether herd immunity was taken into account.

CONCLUSIONS

Our modeling analysis showed that the vaccination of 12-year-old adolescent girls against cervical cancer with the AS04-adjuvanted human papillomavirus 16/18 vaccine would be a cost-effective strategy to prevent cervical cancer in Hungary.

Cost-effectiveness of vaccination with a quadrivalent HPV vaccine in Germany using a dynamic transmission model

INTRODUCTION

Persistent infections with human papillomavirus (HPV) are a necessary cause of cervical cancer and are responsible for important morbidity in men and women. Since 2007, HPV vaccination has been recommended and funded for all girls aged 12 to 17 in Germany. A previously published cost-effectiveness analysis, using a static model, showed that a quadrivalent HPV vaccination programme for 12-year-old girls in Germany would be cost effective. Here we present the results from a dynamic transmission model that can be used to evaluate the impact and cost-effectiveness of different vaccination schemas.

METHODS

We adapted a HPV dynamic transmission model, which has been used in other countries, to the German context. The model was used to compare a cervical cancer screening only strategy with a strategy of combining vaccination of females aged 12-17 years old and cervical cancer screening, based on the current recommendations in Germany. In addition, the impact of increasing vaccination coverage in this cohort of females aged 12-17 years old was evaluated in sensitivity analysis.

RESULTS

The results from this analysis show that the current quadrivalent HPV vaccination programme of females ages 12 to 17 in Germany is cost-effective with an ICER of 5,525€/QALY (quality adjusted life year). The incremental cost-effectiveness ratio (ICER) increased to 10,293€/QALY when the vaccine effects on HPV6/11 diseases were excluded. At steady state, the model predicted that vaccinating girls aged 12 to 17 could reduce the number of HPV 6/11/16/18-related cervical cancers by 65% and genital warts among women and men by 70% and 48%, respectively. The impact on HPV-related disease incidence and costs avoided would occur relatively soon after initiating the vaccine programme, with much of the early impact being due to the prevention of HPV6/11-related genital warts.

CONCLUSIONS

These results show that the current quadrivalent HPV vaccination and cervical cancer screening programmes in Germany will substantially reduce the incidence of cervical cancer, cervical intraepithelial neoplasia (CIN) and genital warts. The evaluated vaccination strategies were all found to be cost-effective. Future analyses should include more HPV-related diseases.

Human papillomavirus vaccination in low-resource countries: lack of evidence to support vaccinating sexually active women

Vaccines against the human papillomaviruses (HPV) that cause around 70% of cervical cancer cases worldwide are highly efficacious when administered before infection with the viruses, which occurs soon after initiation of sexual activity. Despite recommendations from key public health bodies that the primary target population for HPV vaccination should be young adolescent girls, numerous articles have suggested widening the target age group to include older adolescent girls and adult women. These articles cite evidence of efficacy and cost-effectiveness when making recommendations, and they rarely take into account the difficult resource-allocation issues faced by decision makers in low-income countries. Authors and sponsors of these articles are usually from high-income countries and sometimes include vaccine manufacturers. This review discusses the strengths and weaknesses of several types of evidence offered by these papers in support of vaccination of a broad age range of girls and women. It concludes that the greatest public health benefit and value for resources will come from vaccinating girls before sexual debut and exposure to HPV, particularly in low-resource areas.

Spotlight on quadrivalent human papillomavirus (types 6, 11, 16, 18) recombinant vaccine(Gardasil®) in the prevention of premalignant genital lesions, genital cancer, and genital warts in women

Quadrivalent human papilloma virus (HPV) [types 6, 11, 16, 18] recombinant vaccine (Gardasil®; Silgard®) is composed of virus-like particles (VLPs) formed by self-assembly of recombinant L1 capsid protein from each of HPV types 6, 11, 16, and 18. The VLPs are noninfectious, containing no DNA, and are highly immunogenic, inducing high levels of neutralizing antibodies against the particular HPV types when administered to animals or humans. Quadrivalent HPV vaccine is indicated for use from the age of 9 years for the prevention of premalignant genital lesions (cervical, vulvar, and vaginal), cervical cancer, and external genital warts (condyloma acuminata) causally related to certain oncogenic or specific HPV types. In placebo-controlled clinical trials, quadrivalent HPV vaccine administered as three doses over 6 months provided high-level protection against infection or disease caused by the vaccine HPV types over 2-4 years of follow-up in females aged 15-45 years who were naive to the vaccine HPV types. A degree of cross-protection against certain other non-vaccine high-risk HPV types was also observed. The vaccine is not effective against current infection with a vaccine HPV type. Girls or women with current infection with one or more of the vaccine HPV types gained protection from infection or disease caused by the remaining vaccine HPV types and they were also protected against reinfection with the same HPV type after clearance of an infection caused by a vaccine HPV type. High seroconversion rates and high levels of anti-HPV antibodies were observed in all vaccinated individuals of all age ranges from 9 to 45 years. No correlation was found between antibody levels and protective efficacy of the vaccine. Rechallenge with quadrivalent HPV vaccine produced a potent anamnestic humoral immune response. The vaccine is generally well tolerated and is projected to be cost effective in most pharmacoeconomic models. Therefore, quadrivalent HPV vaccine offers an effective means, in combination with screening programs, to substantially reduce the burden of HPV-related precancerous lesions and cancer, particularly cervical cancer, as well as anogenital warts.

Cost-effectiveness of cervical cancer screening with primary human papillomavirus testing in Norway

Background:

New screening technologies and vaccination against human papillomavirus (HPV), the necessary cause of cervical cancer, may impact optimal approaches to prevent cervical cancer. We evaluated the cost-effectiveness of alternative screening strategies to inform cervical cancer prevention guidelines in Norway.

Methods:

We leveraged the primary epidemiologic and economic data from Norway to contextualise a simulation model of HPV-induced cervical cancer. The current cytology-only screening was compared with strategies involving cytology at younger ages and primary HPV-based screening at older ages (31/34+ years), an option being actively deliberated by the Norwegian government. We varied the switch-age, screening interval, and triage strategies for women with HPV-positive results. Uncertainty was evaluated in sensitivity analysis.

Results:

Current cytology-only screening was less effective and more costly than strategies that involve switching to primary HPV testing in older ages. For unvaccinated women, switching at age 34 years to primary HPV testing every 4 years was optimal given the Norwegian cost-effectiveness threshold ($83 000 per year of life saved). For vaccinated women, a 6-year screening interval was cost-effective. When we considered a wider range of strategies, we found that an earlier switch to HPV testing (at age 31 years) may be preferred.

Conclusions:

Strategies involving a switch to HPV testing for primary screening in older women is expected to be cost-effective compared with current recommendations in Norway.

Quadrivalent human papillomavirus (types 6, 11, 16, 18) recombinant vaccine (Gardasil®): a review of its use in the prevention of premalignant genital lesions, genital cancer and genital warts in women

Quadrivalent human papilloma virus (HPV) [types 6, 11, 16, 18] recombinant vaccine (Gardasil®; Silgard®) is composed of virus-like particles (VLPs) formed by self-assembly of recombinant L1 capsid protein from each of HPV types 6, 11, 16 and 18. The VLPs are noninfectious, containing no DNA, and are highly immunogenic, inducing high levels of neutralizing antibodies against the particular HPV types when administered to animals or humans. Quadrivalent HPV vaccine is indicated for use from the age of 9 years for the prevention of premalignant genital lesions (cervical, vulvar and vaginal), cervical cancer and external genital warts (condyloma acuminata) causally related to certain oncogenic or specific HPV types. In placebo-controlled clinical trials, quadrivalent HPV vaccine administered as three doses over 6 months provided high-level protection against infection or disease caused by the vaccine HPV types over 2-4 years of follow-up in females aged 15-45 years who were naive to the vaccine HPV types. A degree of cross-protection against certain other non-vaccine high-risk HPV types was also observed. The vaccine is not effective against current infection with a vaccine HPV type. Girls or women with current infection with one or more of the vaccine HPV types gained protection from infection or disease caused by the remaining vaccine HPV types and they were also protected against reinfection with the same HPV type after clearance of an infection caused by a vaccine HPV type. High seroconversion rates and high levels of anti-HPV antibodies were observed in all vaccinated individuals of all age ranges from 9 to 45 years. No correlation was found between antibody levels and protective efficacy of the vaccine. Rechallenge with quadrivalent HPV vaccine produced a potent anamnestic humoral immune response. The vaccine is generally well tolerated and is projected to be cost effective in most pharmacoeconomic models. Therefore, quadrivalent HPV vaccine offers an effective means, in combination with screening programmes, to substantially reduce the burden of HPV-related precancerous lesions and cancer, particularly cervical cancer, as well as anogenital warts.