Cost-effectiveness of a potential vaccine for human papillomavirus

Human papilloma virus vaccines: A comprehensive narrative review

Cervical cancer is one of the most common cancers in women aged 15-44 years in the world, with more than three-quarters of cases diagnosed at a locally advanced clinical stage with minor prospects of survival. Although only a small percentage of women with Human Papilloma Virus (HPV) develop cervical cancer and most of the HPV infections are cleared subsequently at primary stage itself, but seroconversion not always guarantees that the individual is immune to HPV. The advent of the cervical carcinoma vaccine has raised the expectations that eradication of cervical carcinoma might be possible in the near future as it exhibited remarkably high efficacy against the vaccine-specific types in naive women with no serious vaccine-related adverse events. Few prophylactic HPV vaccines are currently licensed in over 100 countries. It has also been suggested that vaccinating both men and women is more beneficial than vaccinating only females. Vaccination is a cost-effective strategy to reduce the incidence of cervical cancer and mortality compared to no vaccination based on the cost of cancer treatment. Well-coordinated vaccination strategy with focus on adolescent girls and if possible, boys can lead to dramatic impact on disease reduction around the world.

HPV Vaccination Adherence in Working-Age Men: A Systematic Review and Meta-Analysis

BACKGROUND

Human papillomavirus (HPV) infection is the most common sexually transmitted viral infection in the world. HPV vaccination adherence rates in men are generally lower than in women. The aim of this systematic review and meta-analysis was to assess adherence to HPV vaccination in young working-age males (18-30 years old).

METHODS

A systematic review was performed using three databases: PubMed, Scopus, and Web of Science, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA).

RESULTS

After duplicate removal, the initial search resulted in 478 eligible papers. With the exclusion of 425 papers after screening the abstracts, full texts of 53 articles were reviewed. Subsequently, 45 were excluded. Among the eight studies included, four (50%) examined the vaccination adherence in young adults through data registered in nationwide insurance or private companies' databases, three (37.5%) in young adults in different settings through data collected from surveys and questionnaires, and one (12.5%) an HPV vaccination campaign in a family medicine residency practice.

CONCLUSION

Adherence to HPV vaccination in men of working age (18-30 years) does not appear to be adequate (pooled prevalence 11%). In order to achieve a higher level of compliance, it is important to place an emphasis on vaccination campaigns in schools as well as in the workplace, after consultation with and approval from local, regional, and federal public health agencies.

Sequential Targeted Therapy for Advanced, Metastatic, and Recurrent Cervical Cancer: A Cost-Effectiveness Analysis of the Patient Journey

OBJECTIVES

To evaluate outcomes and cost-effectiveness of targeted therapy sequencing for metastatic and recurrent cervical cancer.

METHOD

Models were simulated based on phase II and III trials on bevacizumab (bev) from GOG-240, cemiplimab (cemi) from GOG 3016, pembrolizumab (pembro) from KEYNOTE-826, and tisotumab vedotin (tiso) from GOG 3023. Costs were based on IBM Micromedex RED BOOK™ and company listed costs.

RESULTS

For [chemo + bev → chemo], total cost was $125,918.04, with median overall survival (mOS) of 21.8 months, and cost-effectiveness ratio (CER) of $119,835.79. For [chemo + bev → cemi], total cost was $187,562.99 with mOS of 28.5 months and CER of $162,039.16. For [chemo + bev + pembro → chemo], total cost was $319,963.78 with mOS 32.9 months and CER of $249,930.10. For [chemo + bev + pembro → tiso], total cost was $455,204.45, with mOS 36.5 months and CER of $320,072.99.

CONCLUSION

The combination of immunotherapies and biologics have significantly increased overall survival, but with associated higher costs, primarily related to drug costs.

The Clinical and Economic Impact of a Nonavalent Versus Bivalent Human Papillomavirus National Vaccination Program in Taiwan

OBJECTIVES

This study aimed to estimate the epidemiologic and economic impact of a nonavalent human papillomavirus (HPV) vaccination program for 13- to 14-year-old females compared with that of the bivalent vaccine in Taiwan.

METHODS

A previously developed dynamic transmission model for the nonavalent HPV vaccine was adapted to the Taiwan setting. The natural history of cervical cancer and genital warts was simulated by the HPV model assuming an 80% vaccination coverage rate in girls aged 13 to 14 years of age with a 2-dose schedule for the nonavalent and bivalent HPV vaccines. A lifetime duration of vaccine protection was assumed for the HPV vaccine types.

RESULTS

The model estimated that the nonavalent HPV vaccine would prevent an additional 15 951 cervical cancer cases, 6600 cervical cancer-related deaths, 176 702 grade 2 or grade 3 cervical intraepithelial neoplasia cases, 103 959 grade 1 cervical intraepithelial neoplasia cases, and 1 115 317 genital warts cases compared with the bivalent HPV vaccine. The nonavalent HPV vaccination program was projected to cost an additional New Taiwan dollars (NTD) 675.21 per person and to produce an additional 0.00271 quality-adjusted life-year per person over 100 years compared with the bivalent HPV vaccine. Thus, the incremental cost-effectiveness ratio of the nonavalent HPV vaccine versus the bivalent HPV vaccine was NTD 249 462/quality-adjusted life-year.

CONCLUSIONS

A nonavalent HPV vaccination program for 13- to 14-year-old girls would have additional public health and economic impacts and would be highly cost-effective compared with the bivalent HPV vaccine, relative to per capita gross domestic product, which is estimated at NTD 746 526 for Taiwan.

Cost-Effectiveness of Bivalent, Quadrivalent, and Nonavalent HPV Vaccination in South Africa

BACKGROUND AND OBJECTIVES

In South Africa, the prevalence of human papillomavirus (HPV) and associated diseases, such as cervical cancer and genital warts, is among the highest in the world. This study evaluates the cost-effectiveness of bivalent, quadrivalent, and nonavalent HPV vaccination for 9- to 14-year-old girls from the South African healthcare system perspective.

METHODS

A Markov model portraying the natural HPV disease progression from high-risk infection to cervical intraepithelial neoplasia (CIN) I, CIN II/III, or cervical cancer and from low-risk infection to genital warts was built. Transition probability, utility, and efficacy data were sourced from peer-reviewed literature. Vaccination costs were calculated based on the World Health Organization (WHO) guidelines. The model was populated with a cohort of 520,000 9-year-old girls to calculate incremental cost-effectiveness ratios (ICER) in South African Rand (R) per quality-adjusted life-years (QALYs) gained for each vaccination strategy.

RESULTS

All HPV vaccination strategies dominate the no vaccine strategy. Compared with the bivalent vaccine, the nonavalent strategy increases QALYs by 0.14 and costs by R1793 (ICER: R13,013 per QALY) per person, while the quadrivalent vaccination provides -0.02 incremental QALYs and R1748 costs (ICER: -R116,397 per QALY). Consequently, at the South African willingness-to-pay threshold of R23,630 per QALY, nonavalent vaccination is the preferred strategy, with a probability of 90.2%. Scenario analysis demonstrated that results are influenced by vaccine coverage, efficacy, and duration of efficacy.

CONCLUSIONS

The introduction of nonavalent for bivalent HPV vaccination is a cost-effective intervention in South Africa. HPV vaccination should be part of a multifaceted public health strategy entailing screening, condoms, and education of all stakeholders to reduce the significant burden of sexual transmitted diseases in South Africa. Sex-neutral and catch-up vaccinations are subjects for further research.

Increasing HPV vaccination coverage to prevent oropharyngeal cancer: A cost-effectiveness analysis

The incidence of oropharyngeal cancer (OPC) has been rising, especially among middle-aged men. While Human Papillomavirus (HPV) has been irrevocably implicated in the pathogenesis of oropharyngeal cancer (OPC), the current HPV vaccination uptake rate remains low in the US. The aim of our study was to evaluate the impact of increased HPV vaccination coverage on HPV-associated OPC incidence and costs. A decision analytic model was constructed for hypothetical cohorts of 9-year-old boys and girls. Two strategies were compared: 1) Maintaining the current vaccination uptake rates; 2) Increasing HPV vaccination uptake rates to the Healthy People 2030 target (80%) for both sexes. Increasing HPV vaccination coverage rates to 80% would be expected to prevent 5,339 OPC cases at a cost of $0.57 billion USD. Increased HPV vaccination coverage would result in 7,430 quality-adjusted life year (QALY) gains in the overall population, and it is estimated to be cost-effective for males with an incremental cost-effectiveness ratio of $86,940 per QALY gained under certain conditions. Expanding HPV vaccination rates would likely provide a cost-effective way to reduce the OPC incidence, particularly among males.

Evaluating Risk-Stratified HPV Catch-up Vaccination Strategies: Should We Go beyond Age 26?

BACKGROUND

Human papillomavirus (HPV) is the most common sexually transmitted infection in the United States. HPV can cause genital warts and multiple types of cancers in females. HPV vaccination is recommended to youth age 11 or 12 years before sexual initiation to prevent onset of HPV-related diseases. For females who have not been vaccinated previously, catch-up vaccines are recommended through age 26. The extent to which catch-up vaccines are beneficial in terms of disease prevention and cost-effectiveness is questionable given that some women may have been exposed to HPV before receiving the catch-up vaccination. This study aims to examine whether the cutoff age of catch-up vaccination should be determined based on an individual woman's risk characteristic instead of a one-size-fits-all age 26.

METHODS

We developed a microsimulation model to evaluate multiple clinical outcomes of HPV vaccination for different women based on a number of personal attributes. We modeled the impact of HPV vaccination at different ages on every woman and tracked her course of life to estimate the clinical outcomes that resulted from receiving vaccines. As the simulation model is risk stratified, we used extreme gradient boosting to build an HPV risk model estimating every woman's dynamic HPV risk over time for the lifetime simulation model.

RESULTS

Our study shows that catch-up vaccines still benefit all women after age 26 from the perspective of clinical outcomes. Women facing high risk of HPV infection are expected to gain more health benefits compared with women with low HPV risk.

CONCLUSIONS

From a cancer prevention perspective, this study suggests that the catch-up vaccine after age 26 should be deliberately considered.

Cost-Effectiveness and Budget Impact Analysis of Primary Screening With Human Papillomavirus Test With Genotyping in Argentina

OBJECTIVES

Cervical cancer (ICC) is the fourth leading cause of mortality in women in Argentina and primary screening with conventional cytology (Papanicolaou smear) is the most widely used strategy despite its limitations. Strategies based on human papillomavirus (HPV) testing have the potential to improve detection and reduce mortality. The objective of this study is to evaluate the cost-effectiveness and budgetary impact of a strategy based on HPV testing with genotyping.

METHODS

We used a decision model to compare the ICC screening strategies. The population consisted of 30- to 65-year-old females suitable for screening in Argentina. Inputs comprised epidemiologic, diagnostic performance, and costs data. The clinical impact was represented by the number of ICC detected and ICC-related mortality. Incremental cost-effectiveness ratio, estimated in terms of Argentinean pesos per life-year gained, and the budgetary impact were calculated at 5, 10, and 20 years. Univariate and probabilistic sensitivity analyses were performed.

RESULTS

Primary screening with HPV testing would prevent 1853 ICC deaths and reduce mortality by 13% at year 10 compared with Papanicolaou smear. With an incremental cost-effectiveness ratio of AR$329 042 in the base case, it would be cost-effective for a cost-effectiveness threshold of 1 gross domestic product per capita. It would imply an additional expense in the first 5 years and probably savings in the subsequent ones. Sensitivity analyses confirm the robustness of the findings.

CONCLUSIONS

The primary screening strategy based on HPV testing with genotyping compared with conventional cytology is most likely a cost-effective strategy in Argentina.

The epidemiologic and economic impact of a quadrivalent human papillomavirus vaccine in Thailand

BACKGROUND

The human papillomavirus (HPV) vaccine was introduced into Thailand's national immunization program in 2017 for 11-12 year old school girls. The objectives of this study were to examine the epidemiological consequences and cost-effectiveness of a routine quadrivalent HPV (4vHPV) vaccination and the routine 4vHPV vaccination plus 5-year catch-up vaccination by comparing with cervical cancer screening only (no vaccination) in Thailand.

METHOD

A transmission dynamic model was used to assess the cost-effectiveness of the routine 4vHPV vaccination and the routine 4vHPV vaccination plus catch-up vaccination, compared with no vaccination (screening only) in Thai population. The vaccination coverage rate assumptions were 95% in 11-12-year-old girls for the routine vaccination and 70% in 13-24 year-old females for the 5-year catch-up vaccination. Vaccination costs, direct medical costs of HPV-related diseases, and the number of quality of life years (QALYs) gained were calculated for over a 100-year time horizon with discount rate of 3%.

RESULT

The model indicated that the routine 4vHPV vaccination and the routine plus catch-up 4vHPV vaccination strategies could prevent approximately 434,130 and 472,502 cumulative cases of cervical cancer, 182,234 and 199,068 cumulative deaths from cervical cancer and 12,708,349 and 13,641,398 cumulative cases of HPV 6/11 related genital warts, respectively, when compared with no vaccination over 100 years. The estimated cost per QALY gained (ICER) when compared to no vaccination in Thailand was 8,370 THB/QALY for the routine vaccination and 9,650 THB/QALY for the routine with catch-up vaccination strategy.

CONCLUSION

Considering the recommended threshold of 160,000 THB/QALY for Thailand, the implementation of the routine 4vHPV vaccination either alone or plus the catch-up vaccination was cost-effective as compared to the cervical cancer screening only.

Sensitivity analysis methods in the biomedical sciences

Sensitivity analysis is an important part of a mathematical modeller's toolbox for model analysis. In this review paper, we describe the most frequently used sensitivity techniques, discussing their advantages and limitations, before applying each method to a simple model. Also included is a summary of current software packages, as well as a modeller's guide for carrying out sensitivity analyses. Finally, we apply the popular Morris and Sobol methods to two models with biomedical applications, with the intention of providing a deeper understanding behind both the principles of these methods and the presentation of their results.

Cost-effectiveness of a comprehensive immunization program serving high-risk, uninsured adults

Despite the numerous social and economic benefits of vaccination, adult immunization rates fall far short of recommended levels costing the United States $9 billion annually in health care expenditures and reduced productivity. While it is well recognized that childhood immunization is highly cost-effective, the economic impact of adult immunization programs varies by disease and is influenced by population demographics. This study aimed to assess the cost-effectiveness of a comprehensive adult immunization program serving high-need populations delivered by a local health department (LHD) in partnership with community organizations. We modeled incremental cost-effectiveness taking the payer perspective of each vaccine separately in simulated cohorts of 100,000 over a 20-year horizon using data provided by the LHD and data from the published literature. We adjusted the results to align with actual program delivery and used them to estimate an incremental cost-effectiveness ratio (ICER) for the entire program. We assessed the effects of varying our base model parameters in univariate sensitivity analyses. We discounted benefits and life years saved (LYS) at 3% and adjusted results to 2016 US$. Four of seven disease models were cost-effective (using a $100,000 CE threshold) with ICERS ranging from $14,260 to $79,022/LYS. Sensitivity analyses did not substantially impact the results. The ICER for program as a whole was $67,940/LYS. A community-delivered comprehensive immunization program serving uninsured, low income, high-risk adults is a cost-effective investment even when most do not receive the full regimen of some vaccines.

Clinical evaluation and budget impact analysis of cervical cancer screening using cobas 4800 HPV screening technology in the public sector of South Africa

Cytology remains the mainstay of cervical cancer screening in South Africa (SA), however false negative rates are 25-50%. In contrast, human papillomavirus (HPV) screening techniques have higher sensitivity for cervical cancer precursors. The cobas® 4800 HPV test detects pooled high-risk HPV types and individual genotypes HPV 16 and 18. Using a mathematical budget impact model, the study objective was to evaluate the clinical and budget impact of replacing primary liquid-based cytology (LBC) with primary HPV-based screening strategies. In SA, current LBC screening practice recommends one test every ten years, followed by large loop excision of the transformation zone (LLETZ) if indicated. HPV testing can be performed from an LBC sample, where no additional consultations nor samples are required. In the budget impact model, LBC screening for 2 cycles (one test every ten years) was compared to cobas® 4800 HPV test for 2 cycles (one test every 5 years). The model inputs were gathered from literature and primary data sources. Indicative prices for LBC and cobas® 4800 HPV test were R189 and R457, respectively. Model results indicate that best outcomes for detection of disease were seen using cobas® 4800 HPV test. Forty-eight percent of cervical cancer cases were detected compared to 28% using LBC, and 50% of cervical intraepithelial neoplasia (CIN) 2 and CIN3 cases, compared to 25% with LBC. The budget impact analysis predicted that the cost per detected case of CIN2 or higher would be R 56,835 and R46,980 for the cobas® 4800 HPV and LBC scenarios, respectively. This equates to an incremental cost per detected case of CIN2 or higher of R9 855. From this model we conclude that a primary HPV screening strategy will have a significant clinical impact on disease burden in South Africa.

Cost-Effectiveness Analysis of Human Papillomavirus Vaccination in Adolescent Girls in Taiwan

Objective:

Three vaccines are available to Taiwanese young girls for cervical cancer (CC) prevention. Here we evaluate the cost-effectiveness of the two-dose (2D) AS04-adjuvanted HPV-16/18 vaccine (2D-AS04-HPV-16/18v)+screening compared with a screening programme alone, with 2D human papillomavirus 6/11/16/18 vaccine (2D-4vHPVv)+screening, and with 2D/three-dose (3D) human papillomavirus 6/11/16/18/31/33/45/52/58 vaccine (9vHPVv)+screening, for Taiwan universal mass vaccination.

Methods:

A static Markov cohort model simulated the natural history of human papillomavirus (HPV) infection and CC screening for a 12-year-old cohort of Taiwanese girls (N=120,000). The model ran in 1-year cycles over the cohort’s lifetime. Vaccine efficacy irrespective of HPV type was considered in the analysis for each vaccine. Input data were obtained from published literature, local databases, government reports and websites, and expert opinion. The analysis incorporated direct medical costs only, with an annual discount rate of 3.0%. The threshold was determined as 1 Gross Domestic Product per capita (New Taiwan dollar [NT$] 727,818; year 2016).

Results:

The 2D-AS04-HPV-16/18v+screening yielded 0.0365 quality-adjusted life year (QALY) gained at an additional cost of NT$ 5,770 per person compared with the screening programme alone. This resulted in an incremental cost-effectiveness ratio well below the threshold. Compared with 2D-4vHPVv+screening and 2D/3D-9vHPVv+screening, discounted results demonstrated additional QALYs gained at lower cost for 2D-AS04-HPV-16/18v+screening, making it dominant over both 2D-4vHPVv+screening and 2D/3D-9vHPVv+screening.

Conclusions:

Vaccinating Taiwanese girls with 2D-AS04-HPV-16/18v in addition to screening to prevent CC is cost-effective compared with using a screening programme alone and the dominant option compared with 2D-4vHPVv+screening and 2D/3D-9vHPVv+screening.

Vaccination against HPV virus: a systematic review of economic evaluation studies for developed countries

INTRODUCTION

During the last years, a significant number economic evaluations of HPV vaccination has been published. Given that cost-effectiveness constitutes an essential part of decision-making with regards to the reimbursement of a health technology, the purpose of this study is to provide a supportive tool to decision-makers regarding the economic efficiency of the introduction of HPV vaccination to national immunization programs.

AREAS COVERED

The PubMed database was searched in order to identify cost-effectiveness studies for HPV vaccination. A total of 42 articles were finally retrieved. All retrieved cost-effectiveness ratios (ICERs) were converted in the same currency unit (I$) and then inflated to the same year (2015) in order to facilitate cross-country comparisons.

RESULTS

Overall, vaccination against HPV 6,11,16,18 types appears to have a ICER with mean value of I$25132/QALY, whereas the mean ICER of vaccination against oncogenic HPV 16,18 types is estimated at I$38,253/QALY.

EXPERT COMMENTARY

HPV vaccination would be a cost-effective intervention in the setting of high-income countries and could reduce the incidence of HPV-related diseases.

Epidemiology of Anal Canal Cancer

Anal cancer is a rare malignancy, although its incidence has been increasingly in recent decades. This article discusses risk factors for anal cancer and how these risk factors affect the changing demographics of this disease.

Ten Years of Human Papillomavirus Vaccination in the United States

Since human papillomavirus (HPV) vaccine was first introduced for females in the United States in 2006, vaccination policy has evolved as additional HPV vaccines were licensed and new data became available. The United States adopted a gender neutral routine HPV immunization policy in 2011, the first country to do so. Vaccination coverage is increasing, although it remains lower than for other vaccines recommended for adolescents. There are various reasons for low coverage, and efforts are ongoing to increase vaccine uptake. The safety profile of HPV vaccine has been well established from 10 years of postlicensure monitoring. Despite low coverage, the early effects of the HPV vaccination program have exceeded expectations.

Cost-effectiveness of two-dose human papillomavirus vaccination in Singapore

INTRODUCTION

Cervical cancer is the tenth most common cancer and the eighth most frequent cause of death among women in Singapore. As human papillomavirus (HPV) infection is the necessary cause of cervical cancer, the risk of cervical cancer can be substantially reduced through vaccination. This study was conducted to evaluate the cost-effectiveness of two-dose HPV vaccination as part of a national vaccination programme for 12-year-old girls in Singapore, from the perspective of the healthcare payer.

METHODS

A lifetime Markov cohort model was used to evaluate the cost-effectiveness of introducing the AS04-adjuvanted HPV-16/18 vaccine (AS04-HPV-16/18v) to the current cervical screening programme in Singapore. Furthermore, the cost-effectiveness of the AS04-HPV-16/18v was compared with the HPV-6/11/16/18 vaccine (4vHPV). Model inputs were derived from local data, where possible, and validated by clinical experts in Singapore.

RESULTS

Introduction of the AS04-HPV-16/18v in Singapore was shown to prevent 137 cervical cancer cases and 48 cervical cancer deaths when compared with screening alone. This resulted in an incremental cost-effectiveness ratio of SGD 12,645 per quality-adjusted life year (QALY) gained, which is cost-effective according to the World Health Organization threshold for Singapore. When discounted at 3%, AS04-HPV-16/18v was dominant over 4vHPV, with cost savings of SGD 80,559 and 28 additional QALYs gained. In the one-way sensitivity analysis, AS04-HPV-16/18v remained cost-effective compared with screening alone and dominant compared with 4vHPV.

CONCLUSION

AS04-HPV-16/18v is the most cost-effective choice for reducing the burden of cervical cancer through universal mass vaccination for 12-year-old girls in Singapore.

Organised screening for cervical cancer in France: a cost-effectiveness assessment

OBJECTIVE

According to the third cancer plan, organised screening (OS) of cervical cancer (CC) among women aged 25-65 years should be implemented in France in the forthcoming years. The most efficient way to implement OS in the French healthcare system is yet to be determined.

METHODS

A microsimulation model was developed adopting a collective 'all payers' perspective. A closed cohort of women eligible for CC screening and representative in terms of age and participation in individual screening (IndScr) by annual Papanicolaou (Pap) testing every 3 years was modelled on a lifetime horizon. Different OS strategies, additive to IndScr with a 61.9% participation rate based on mailed invitations to non-participant women to perform OS were assessed. Similar modalities were applied to OS and IndScr participants. Strategies implied different screening tests (Papanicolaou (Pap) test, human papillomavirus (HPV) test and p16/Ki67 double staining) and OS periodicity.

RESULTS

Compared with IndScr only, all OS strategies were associated with decreased cancer incidence/mortality (from 14.2%/13.5% to 22.9%/25.8%). Most strategies generated extra costs ranging from €37.9 to €1607 per eligible woman. HPV testing every 10 and 5 years were cost saving. HPV tests every 10 and 5 years were the most efficient strategies, generating more survival at lower costs than Pap-based strategies. Compared to IndScr only, an HPV test every 10 years was cost saving. The most effective strategies were p16/Ki67 as primary or HPV positive confirmation tests, with respective incremental cost-effectiveness ratios of €6 541 250 and €101 391 per life year. Pap-based strategies generated intermediary results.

CONCLUSION

OS strategies based on the HPV test appear highly efficient. However, our results rely on the assumption that women and practitioners comply with the recommended OS periodicities (3, 5, 10 years). Implementing these OS modalities will require major adaptations to the current CC screening organisation. Pap test-based strategies might be simpler to setup while preparing an appropriate implementation of more efficient OS screening modalities.

Adolescent Immunization: Challenges and Opportunities

Immunization is one of the greatest public health achievements of the past century. Vaccines are responsible for the worldwide eradication of smallpox, the elimination of polio in the western hemisphere, and most recently the elimination of rubella as a public health threat in the United States. Childhood vaccination rates are at an all-time high, but immunization falls off dramatically during adolescence (ages 11–19). With increased attention being paid to adolescent health and the new vaccines available for adolescents, efforts to increase adolescent immunization rates are moving to the forefront. Improving adolescent immunization rates requires advocacy on the part of all health professionals. School nurses, whose mission is to enhance the well-being of adolescents, are in a unique position to work with students, parents, and local health professionals to improve the adolescent immunization rate.

Facilitators and barriers to the acceptance of human papillomavirus (HPV) vaccination among adolescent girls: a comparison between mothers and their adolescent daughters in Hong Kong

BACKGROUND

The aim of this study is to examine knowledge and attitude as facilitators and barriers to the acceptance of HPV vaccination for adolescent girls by mothers and adolescent girls.

METHODS

A cross-sectional survey conducted in Hong Kong in January 2010. Adolescent girls aged 12-18, together with their mothers, were recruited to complete two separate questionnaires with similar questions.

RESULTS

A total of 170 mother-adolescent girl dyads were recruited. When the daughters and mothers were compared, the mothers were found to be more aware of "the risk of becoming infected with HPV through early sexual intercourse," while more daughters than mothers knew that "the HPV virus cannot be cured with antibiotics." Significantly more daughters perceived that they had a "chance of being infected with HPV and getting cervical cancer without the vaccine," while more mothers were concerned that "vaccinating for HPV will cause a girl to be stigmatized as promiscuous" and thought that their "adolescent daughters are too young to receive the HPV vaccine." The major predictive factor for the acceptance of the HPV vaccine among mothers was "The HPV vaccine is safe" (OR = 10.126, 95% CI 2.47-41.54). Among daughters who accepted the vaccine, the predictive factor was "The HPV vaccine can prevent most HPV infections" (OR = 6.274, 95% CI 1.93-20.42).

CONCLUSIONS

The findings provide healthcare professionals with a better understanding of the differences between mothers and adolescent girls in knowledge, attitude, and potential factors associated with acceptance of the HPV vaccine. Health professionals should promote the early prevention of HPV infection and eliminate the stigma surrounding HPV vaccination to increase its acceptance. The government should provide financial support for adolescent girls to receive the vaccination in school.

Systematic review of cost-effectiveness analyses for combinations of prevention strategies against human papillomavirus (HPV) infection: a general trend

BACKGROUND

Due to the arrival of multi-valent HPV vaccines, it is more and more important to have a better understanding of the relationship between vaccination and screening programmes. This review aimed to: (1) collect published evidence on the cost-effectiveness profile of different HPV prevention strategies and, in particular, those combining vaccination with changes in screening practices; (2) explore the cost-effectiveness of alternative preventive strategies based on screening and vaccination.

METHODS

A systematic literature review was conducted in order to identify the relevant studies regarding the cost-effectiveness of prevention strategies against HPV infection. Analysis comparing the modelling approaches between studies was made along with an assessment of the magnitude of impact of several factors on the cost-effectiveness of different screening strategies.

RESULTS

A total of 18 papers were quantitatively summarised within the narrative. A high degree of heterogeneity was found in terms of how HPV prevention strategies have been assessed in terms of their economic and epidemiological impact, with variation in screening practice and valence of HPV vaccination found to have large implications in terms of cost-effectiveness.

CONCLUSIONS

This review demonstrated synergies between screening and vaccination. New prevention strategies involving multi-valence vaccination, HPV DNA test screening, delayed commencement and frequency of screening could be implemented in the future. Strategies implemented in the future should be chosen with care, and informed knowledge of the potential impact of all possible prevention strategies. Highlighted in this review is the difficulty in assessing multiple strategies. Appropriate modelling techniques will need to be utilised to assess the most cost-effective strategies.

Cost-effectiveness analysis of AS04-adjuvanted human papillomavirus 16/18 vaccine compared with human papillomavirus 6/11/16/18 vaccine in the Philippines, with the new 2-dose schedule

Cervical cancer (CC) is the second leading cause of cancer death among Filipino women. Human papillomavirus (HPV) vaccination protects against CC. Two vaccines (AS04-HPV-16/18 and 4vHPV) are approved in the Philippines; they were originally developed for a 3-dose (3D) administration and have recently been approved in a 2-dose schedule (2D). This study aims to evaluate the cost-effectiveness of HPV vaccination of 13-year-old Filipino girls, in addition to current screening, in the new 2D schedule. An existing static lifetime, one-year cycle Markov cohort model was adapted to the Philippine settings to simulate the natural history of low-risk and oncogenic HPV infection, the effects of screening and vaccination of a 13-year-old girls cohort vaccinated with either the 2D-AS04-HPV-16/18 or 2D-4vHPV assuming a 100% vaccination coverage. Incremental cost, quality-adjusted life year (QALY) and cost-effectiveness were derived from these estimates. Input data were obtained from published sources and Delphi panel, using country-specific data where possible. Sensitivity analyses were performed to assess the robustness of the model. The model estimated that 2D-AS04-HPV-16/18 prevented 986 additional CC cases and 399 CC deaths (undiscounted), as well as 555 increased QALY (discounted), and save 228.1 million Philippine pesos (PHP) compared with the 2D-4vHPV. In conclusion, AS04-HPV-16/18 is shown to be dominant over 4vHPV in the Philippines, with greater estimated health benefits and lower costs.

Estimating long-term clinical effectiveness and cost-effectiveness of HPV 16/18 vaccine in China

BACKGROUND

Human papillomavirus (HPV) 16 and 18 are the two most common HPV oncogenic types that can be prevented by vaccination. This study aimed at assessing the cost-effectiveness of 3 doses of the bivalent HPV vaccine in rural and urban settings in China.

METHODS

A Markov model was adapted to reflect the lifetime of a modelled 100,000 12-year-old girls cohort in rural and urban settings in China. Input parameters were obtained from published literature, official reports and a two-round expert review panel. Clinical and economic outcomes of vaccination at age 12 with screening was compared to screening only. In the base case analysis, a 3 % discount rate, the vaccine cost of 247 CNY (US$ 39, PAHO vaccine cost in 2013), two rounds of screening in a life time and 70 % coverage for both screening and vaccination were used. One-way, two-way and probabilistic sensitivity analyses were performed. We used different thresholds of cost-effectiveness to reflect the diversity of economic development in China.

RESULTS

Vaccination in addition to screening could prevent 60 % more cervical cancer cases and deaths than screening only. The incremental cost effectiveness ratio varied largely when changing cost of vaccination and discount in one way analysis. Vaccination was very cost-effective when the vaccine cost ranged 87-630 CNY (US$ 13.8-100) in rural and 87-750 CNY (US$ 13.8-119) in urban; and remained cost-effective when the vaccine cost ranged 630-1,700 CNY (US$ 100-270) in rural and 750-1,900 CNY (US$ 119-302) in urban in two way analysis. Probabilistic sensitivity analyses showed that model results were robust.

CONCLUSIONS

In both rural and urban, the vaccination cost and discounting are important factors determining the cost-effectiveness of HPV vaccination; policy makers in China should take these into account when making a decision on the introduction of HPV vaccine. In areas with a high burden of cervical cancer and limited screening activities, HPV vaccination should be prioritized. However, the vaccine cost needs to be reduced in order to make it very cost-effective and affordable as well, in particular in poverty areas with high disease burden.

Extending the Human Papillomavirus Vaccination Programme to Include Males in High-Income Countries: A Systematic Review of the Cost-Effectiveness Studies

BACKGROUND AND OBJECTIVES

Giving the human papillomavirus (HPV) vaccination to females has been shown to be cost-effective in most countries. The epidemiological evidence and economic burden of HPV-related diseases have gradually been shown to be gender neutral. Randomized clinical trials report high efficacy, immunogenicity and safety of the HPV vaccine in males aged 16-26 years. Some pioneering countries extended their HPV vaccination programme to include males, regardless of the cost-effectiveness analysis results. Nevertheless, decision makers need evidence provided by modelling and economic studies to justify the funding of mass vaccination. This systematic review aims to assess the cost-effectiveness of extending the HPV vaccination programme to include males living in high-income countries.

METHODS

A systematic review of the cost-effectiveness analyses of HPV vaccination in males was performed. Data were extracted and analysed using a checklist adapted from the Consolidated Health Economic Evaluation Reporting Standards Statement.

RESULTS

Seventeen studies and 12 underlying mathematical models were identified. Model filiation showed evolution in time from aggregate models (static and dynamic) to individual-based models. When considering the health outcomes HPV vaccines are licensed for, regardless of modelling approaches and assumptions, extending vaccinations to males is rarely found to be cost-effective in heterosexual populations. Cost-effectiveness ratios become more attractive when all HPV-related diseases are considered and when vaccine coverage in females is below 40%.

CONCLUSION

Targeted vaccination of men who have sex with men (MSM) seems to be the best cost-effectiveness option. The feasibility of this strategy is still an open question, since early identification of this specific population remains difficult.

The impact and cost-effectiveness of nonavalent HPV vaccination in the United States: Estimates from a simplified transmission model

INTRODUCTION

The objective of this study was to assess the incremental costs and benefits of the 9-valent HPV vaccine (9vHPV) compared with the quadrivalent HPV vaccine (4vHPV). Like 4vHPV, 9vHPV protects against HPV types 6, 11, 16, and 18. 9vHPV also protects against 5 additional HPV types 31, 33, 45, 52, and 58.

METHODS

We adapted a previously published model of the impact and cost-effectiveness of 4vHPV to include the 5 additional HPV types in 9vHPV. The vaccine strategies we examined were (1) 4vHPV for males and females; (2) 9vHPV for females and 4vHPV for males; and (3) 9vHPV for males and females. In the base case, 9vHPV cost $13 more per dose than 4vHPV, based on available vaccine price information.

RESULTS

Providing 9vHPV to females compared with 4vHPV for females (assuming 4vHPV for males in both scenarios) was cost-saving regardless of whether or not cross-protection for 4vHPV was assumed. The cost per quality-adjusted life year (QALY) gained by 9vHPV for both sexes (compared with 4vHPV for both sexes) was < $0 (cost-saving) when assuming no cross-protection for 4vHPV and $8,600 when assuming cross-protection for 4vHPV.

CONCLUSIONS

Compared with a vaccination program of 4vHPV for both sexes, a vaccination program of 9vHPV for both sexes can improve health outcomes and can be cost-saving.

Economic evaluation of pediatric influenza immunization program compared with other pediatric immunization programs: A systematic review

This study compared the economic value of pediatric immunisation programmes for influenza to those for rotavirus (RV), meningococcal disease (MD), pneumococcal disease (PD), human papillomavirus (HPV), hepatitis B (Hep B), and varicella reported in recent (2000 onwards) cost-effectiveness (CE) studies identified in a systematic review of PubMed, health technology, and vaccination databases. The systematic review yielded 51 economic evaluation studies of pediatric immunisation - 10 (20%) for influenza and 41 (80%) for the other selected diseases. The quality of the eligible articles was assessed using Drummond's checklist. Although inherent challenges and limitations exist when comparing economic evaluations of immunisation programmes, an overall comparison of the included studies demonstrated cost-effectiveness/cost saving for influenza from a European-Union-Five (EU5) and United States (US) perspective; point estimates for cost/quality-adjusted life-years (QALY) from dominance (cost-saving with more effect) to ≤45,444 were reported. The economic value of influenza programmes was comparable to the other vaccines of interest, with cost/QALY in general considerably lower than RV, Hep B, MD and PD. Independent of the perspective and type of analysis, the economic impact of a pediatric influenza immunisation program was influenced by vaccine efficacy, immunisation coverage, costs, and most significantly by herd immunity. This review suggests that pediatric influenza immunisation may offer a cost effective strategy when compared with HPV and varicella and possibly more value compared with other childhood vaccines (RV, Hep B, MD and PD).

Effect of vaccination age on cost-effectiveness of human papillomavirus vaccination against cervical cancer in China

Background

The cost-effectiveness of human papillomavirus (HPV) vaccination in women pre-sexual debut has been demonstrated in many countries. This study aimed to estimate the cost-effectiveness of a 3-dose bivalent HPV vaccination at ages 12 to 55 year in both rural and urban settings in China.

Methods

The Markov cohort model simulated the natural history of HPV infection and included the effect of screening and HPV vaccination over the lifetime of a 100,000 female cohort. Transition probabilities and utilities were obtained from published literature. Cost data were estimated by Delphi panel using healthcare payers’ perspective. Vaccine cost was assumed Hong Kong listed price. Vaccine efficacy (VE) was based on the PATRICIA trial data assuming VE irrespective of HPV type at all ages on incident HPV. Costs and outcomes were discounted at 3 %. Cervical cancer cases and incremental cost-effectiveness ratio (ICER) for vaccination and screening compared with screening alone were estimated for each vaccination age. Reduced VE in women post-sexual debut were investigated in scenario analyses.

Results

With 70 % vaccination coverage, a reduction of cancer cases varying from 585 to 33 in rural and 691 to 32 in urban were estimated at ages 12 to 55, respectively. The discounted ICERs of vaccination at any age under 23 years in rural and any age under 25 years in urban were lower than the current threshold. Scenario analyses with lower VE post-sexual debut confirmed the results with age 20 in rural and 21 in urban had consistent lower ICERs. The more ‘catch-up’ cohorts vaccinated at the start of a program, the more cancer lesions are avoided in the long-term.

Conclusions

Vaccination at any age under 23 years old in rural and any age under 25 years old in urban were cost-effective. Catch-up to the age of 25 years in rural and urban could still be cost-effective.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2207-3) contains supplementary material, which is available to authorized users.

The Dynamics of HPV Infection and Cervical Cancer Cells

The development of cervical cells from normal cells infected by human papillomavirus into invasive cancer cells can be modeled using population dynamics of the cells and free virus. The cell populations are separated into four compartments: susceptible cells, infected cells, precancerous cells and cancer cells. The model system of differential equations also has a free virus compartment in the system, which infect normal cells. We analyze the local stability of the equilibrium points of the model and investigate the parameters, which play an important role in the progression toward invasive cancer. By simulation, we investigate the boundary between initial conditions of solutions, which tend to stable equilibrium point, representing controlled infection, and those which tend to unbounded growth of the cancer cell population. Parameters affected by drug treatment are varied, and their effect on the risk of cancer progression is explored.

Cost effectiveness of human papillomavirus-16/18 genotyping in cervical cancer screening

BACKGROUND

There is limited understanding of the health economic implications of cervical screening with human papillomavirus (HPV)-16/18 genotyping.

OBJECTIVE

The aim of this study was to evaluate the cost effectiveness of cervical cancer primary screening with a HPV-16/18 genotyping test which simultaneously detects 12 other high-risk HPV types.

METHODS

A Markov cohort model compared four strategies: (1) cytology with reflex HPV testing for atypical squamous cells of undetermined significance (ASC-US); (2) co-testing with cytology and HPV testing; (3) HPV with reflex to cytology; and (4) HPV with 16/18 genotyping and reflex cytology (ASC-US threshold). Screening began at age 30 and was performed triennially over 40 years. Screening sensitivity and specificity values for cervical intraepithelial neoplasia (CIN) 3 were obtained from the Addressing THE Need for Advanced HPV Diagnostics (ATHENA) trial. Outcomes for a 1-year follow-up scenario wherein persistent disease was detected were estimated. Screening and cancer treatment costs were calculated from a US payer's perspective in 2013. Costs and quality-adjusted life-years (QALYs) were discounted at 3 % annually.

RESULTS

Applying a US$50,000/QALY threshold, strategy (4) dominated strategies (2) and (3) by reducing costs and cancer incidence and improving QALYs, and was cost effective versus strategy (1). Accounting for persistent ≥CIN 3 at 1 year, strategy (4) was cost effective versus all other strategies. Detecting HPV-16/18 resulted in earlier diagnosis of clinically relevant ≥CIN 3 at initial screening and efficient use of follow-up resources. Outcomes were most influenced by strategy performance.

CONCLUSIONS

Incorporating HPV-16/18 genotyping is cost effective and may improve detection of CIN, thereby preventing cervical cancer.

Applying a Simple Model of Cost Effectiveness Study of HPV Vaccine for Iran

HPV vaccine has been recently added to the Iran Drug List, so decision makers need information beyond that available from RCTs to recommend funding for this vaccination. Modeling and economic studies have addressed some of those information needs. We reviewed cost effectiveness studies to find a suitable model for Iranian population to determine the potential cost effectiveness of HPV vaccine program based on domestic available epidemiologic data. Articles were obtained from an extensive literature search to determine the cost effectiveness of implementing an HPV vaccination program with routine cervical cancer screening. A total of 64 studies were included in this review. Although the studies used different model structures, baseline parameters and assumptions (either a Markov, Hybrid, or Dynamic model). Most of the proposed cost effectiveness models need to model the probability of HPV acquisition, the possible progression from HPV infection to CIN I, CIN II, CIN III and cervical cancer, the probability of HPV transmission which are not available in Iranian epidemiologic data. Based on the available epidemiologic data in Iran, the simplified and it requires substantially fewer assumptions than the other more complex Markov and hybrid models, therefore we decided to use this model for the evaluation of cost effectiveness of HPV vaccine in Iran.

Cost-Effectiveness Evaluation of Quadrivalent Human Papilloma Virus Vaccine for HPV-Related Disease in Iran

Human Papilloma Virus (HPV) vaccine has been added recently to the Iran Drug List. So, decision makers need information beyond that available from RCTs to recommend funding for this vaccination program to add it to the National Immunization program in Iran. Modeling and economic studies have addressed some of those information needs in foreign countries. In order to determine the long term benefit of this vaccine and impact of vaccine program on the future rate of cervical cancer in Iran, we described a model, based on the available economic and health effects of human papilloma virus (HPV), to estimate the cost-effectiveness of HPV vaccination of 15-year-old girls in Iran. Our objective is to estimate the cost-effectiveness of HPV vaccination in Iran against cervical cancer based on available data; incremental cost-effectiveness ratio (ICER) calculations were based on a model comparing a cohort of 15-year-old girls with and without vaccination. We developed a static model based on available data in Iran on the epidemiology of HPV related health outcome. The model compared the cohort of all 15-year old girls alive in the year 2013 with and without vaccination. The cost per QALY, which was found based on our assumption for the vaccination of 15-years old girl to current situation was 439,000,000 Iranian Rial rate (IRR). By considering the key parameters in our sensitivity analysis, value varied from 251,000,000 IRR to 842,000,000 IRR. In conclusion, quadrivalent HPV vaccine (Gardasil) is not cost-effective in Iran based on the base-case parameters value.

A NOVEL APPLICATION OF A CLASSICAL METHOD FOR CALCULATING THE BASIC REPRODUCTIVE NUMBER, R0 FOR A GENDER AND RISK STRUCTURED TRANSMISSION DYNAMIC MODEL OF HUMAN PAPILLOMAVIRUS INFECTION

Mathematical models are increasingly being used in the evaluation of control strategies for infectious disease such as the vaccination program for the Human Papillomavirus (HPV). Here, an ordinary differential equation (ODE) transmission dynamic model for HPV is presented and analyzed. Parameter values for a gender and risk structured model are estimated by calibrating the model around the known prevalence of infection. The effect on gender and risk sub-group prevalence induced by varying the epidemiological parameters are investigated. Finally, the outcomes of this model are applied using a classical mathematical method for calculating R0 in a heterogeneous mixing population. Estimates for R0 under various gender and mixing scenarios are presented.

Cost-effectiveness analysis of the bivalent and quadrivalent human papillomavirus vaccines from a societal perspective in Colombia

Objective

To compare costs and effectiveness of three strategies used against cervical cancer (CC) and genital warts: (i) Screening for CC; (ii) Bivalent Human Papillomavirus (HPV) 16/18 vaccine added to screening; (iii) Quadrivalent HPV 6/11/16/18 vaccine added to screening.

Methods

A Markov model was designed in order to simulate the natural history of the disease from 12 years of age (vaccination) until death. Transition probabilities were selected or adjusted to match the HPV infection profile in Colombia. A systematic review was undertaken in order to derive efficacy values for the two vaccines as well as for the operational characteristics of the cytology test. The societal perspective was used. Effectiveness was measured in number of averted Disability Adjusted Life Years (DALYS).

Results

At commercial prices reported for 2010 the two vaccines were shown to be non-cost-effective alternatives when compared with the existing screening strategy. Sensitivity analyses showed that results are affected by the cost of vaccines and their efficacy values, making it difficult to determine with certainty which of the two vaccines has the best cost-effectiveness profile. To be ‘cost-effective’ vaccines should cost between 141 and 147 USD (Unite States Dollars) per vaccinated girl at the most. But at lower prices such as those recommended by WHO or the price of other vaccines in Colombia, HPV vaccination could be considered very cost-effective.

Conclusions

HPV vaccination could be a convenient alternative for the prevention of CC in Colombia. However, the price of the vaccine should be lower for this vaccination strategy to be cost-effective. It is also important to take into consideration the willingness to pay, budgetary impact, and program implications, in order to determine the relevance of a vaccination program in this country, as well as which vaccine should be selected for use in the program.

A novel method to value real options in health care: the case of a multicohort human papillomavirus vaccination strategy

BACKGROUND

A large number of economic evaluations have already confirmed the cost-effectiveness of different human papillomavirus (HPV) vaccination strategies. Standard analyses might not capture the full economic value of novel vaccination programs because the cost-effectiveness paradigm fails to take into account the value of active management. Management decisions can be seen as real options, a term used to refer to the application of option pricing theory to the valuation of investments in nonfinancial assets in which much of the value is attributable to flexibility and learning over time.

OBJECTIVE

The aim of this article was to discuss the potential advantages shown by using the payoff method in the valuation of the cost-effectiveness of competing HPV immunization programs.

METHODS

This was the first study, to the best of our knowledge, to use the payoff method to determine the real option values of 4 different HPV vaccination strategies targeting female subjects aged 12, 15, 18, and 25 years. The payoff method derives the real option value from the triangular payoff distribution of the project's net present value, which is treated as a triangular fuzzy number. To inform the real option model, cost-effectiveness data were derived from an empirically calibrated Bayesian model designed to assess the cost-effectiveness of a multicohort HPV vaccination strategy in the context of the current cervical cancer screening program in Italy. A net health benefit approach was used to calculate the expected fuzzy net present value for each of the 4 vaccination strategies evaluated.

RESULTS

Costs per quality-adjusted life-year gained seemed to be related to the number of cohorts targeted: a single cohort of girls aged 12 years (€10,955 [95% CI, -1,021 to 28,212]) revealed the lowest cost among the 4 alternative strategies evaluated. The real option valuation challenged the cost-effectiveness dominance of a single cohort of 12-year-old girls. The simultaneous vaccination of 2 cohorts of girls aged 12 and 15 years yielded a real option value (€17,723) equivalent to that attributed to a single cohort of 12-year-old girls (€17,460).

CONCLUSIONS

The payoff method showed distinctive advantages in the valuation of the cost-effectiveness of competing health care interventions, essentially determined by the replacement of the nonfuzzy numbers that are commonly used in cost-effectiveness analysis models, with fuzzy numbers as an input to inform the real option pricing method. The real option approach to value uncertainty makes policy making in health care an evolutionary process and creates a new "space" for decision-making choices.

Direct costs of cervical cancer management in Morocco

BACKGROUND

For cervical cancer the epidemiological profile is poorly known in Morocco and no data is available concerning the direct medical costs. The purpose of this work is to estimate the direct cost of medical management of invasive cervical cancer during the first year after diagnosis in Morocco.

METHODS

The estimation of direct costs of medical management of invasive cervical cancer during the first year after diagnosis in Morocco is based on the estimation of individual cost in each stage which covers diagnosis, treatment and follow-up during first year. The cost was estimated per patient and whole cycle-set using the costs for each drug and procedure as indicated by the Moroccan National Agency for Health Insurance. Extrapolation of the results to the whole country was used to calculate the total annual cost of cervical cancer treatments in Morocco.

RESULTS

Overall approximately 1,978 new cases of cervical cancer occur each year in Morocco. The majority (82.96%) of these cases were diagnosed at a late stage (stage II or more). The cost of one case of cervical cancer depends on stage of diagnosis, the lowest cost is $382 for stage Cis followed by the cost of stage IA1 for young women (<40 years) which is $2,952. The highest cost is for stage IV, which is $7,827. The total cost of cervical cancer care for one year after diagnosis is estimated at $13,589,360. The share allocated to treatment is the most important part of the global care budget with an annual sum of $13,027,609 whereas other cost components are represented as follows: $435,694 for annual follow-up activity and $126,057 for diagnosis and preclinical staging.

CONCLUSION

This study provides health decision-makers with a first estimate of costs and the opportunity to achieve the optimal use of available data to estimate the needs of health facilities in Morocco.

Modeling the impact of quadrivalent HPV vaccination on the incidence of Pap test abnormalities in the United States

BACKGROUND

We present data on Pap test results and HPV prevalence from the HPV Sentinel Surveillance project, a multiyear surveillance project enrolling women from a diverse set of 26 clinics throughout the US from 2003 to 2005. We use mathematical modeling to illustrate the potential timing and magnitude of decreases in Pap test abnormalities in sexually transmitted disease (STD), family planning, and primary care clinics in the US as a result of HPV vaccination.

METHODS

The probability of an abnormal Pap result was based on three factors: (1) infection with HPV 16/18, or both; (2) infection with high-risk HPV types other than HPV 16/18; and (3) infection with HPV 6/11, or both. We estimated the relative reduction in the probability of an abnormal Pap result over the first 25 years of a female-only, quadrivalent HPV vaccination program, compared to a scenario of no HPV vaccination in which the probability of abnormal Pap results was assumed constant.

RESULTS

The probability of an abnormal Pap result ranged from 7.0% for the lowest risk group (those without any high-risk HPV types and without HPV 6/11) to 45.2% for the highest risk group (those with HPV 16/18 and at least one other high-risk HPV type). Estimated reductions in abnormal Pap results among women in the 21- to 29-year age group were 0.8%, 10.2%, and 11.3% in years 5, 15, and 25 of the vaccine program respectively, in the lower vaccine coverage scenario, and 7.4%, 21.4%, and 22.2%, respectively, in the higher coverage scenario.

CONCLUSIONS

Our results suggest that HPV vaccination will have a discernable impact on the probability of Pap abnormalities, but the timing and magnitude of the reduction will depend substantially on vaccine coverage and the degree of cross-protection against high risk HPV types other than HPV 16/18.

Aggregation and competitive exclusion: explaining the coexistence of human Papillomavirus types and the effectiveness of limited vaccine conferred cross-immunity

Human Papillomavirus (HPV) types are sexually transmitted infections that cause a number of human cancers. According to the competitive exclusion principle in ecology, HPV types that have lower transmission probabilities and shorter durations of infection should be outcompeted by more virulent types. This, however, is not the case, as numerous HPV types co-exist, some which are less transmissible and more easily cleared than others. This paper examines whether this exception to the competitive exclusion principle can be explained by the aggregation of infection with HPV types, which results in patchy spatial distributions of infection, and what implications this has for the effect of vaccination on multiple HPV types. A deterministic transmission model is presented that models the patchy distribution of infected individuals using Lloyd's mean crowding. It is first shown that higher aggregation can result in a reduced capacity for onward transmission and reduce the required efficacy of vaccination. It is shown that greater patchiness in the distribution of lower prevalence HPV types permits co-existence. This affirms the hypothesis that the aggregation of HPV types provides an explanation for the violation of the competitive exclusion principle. Greater aggregation of lower prevalence types has important implications where type-specific HPV vaccines also offer cross-protection against non-target types. It is demonstrated that the degree of cross-protection can be less than the degree of vaccine protection conferred against directly targeted types and still result in the elimination of non-target types when these non-target types are patchily distributed.

Inference of type-specific HPV transmissibility, progression and clearance rates: a mathematical modelling approach

Quantifying rates governing the clearance of Human Papillomavirus (HPV) and its progression to clinical disease, together with viral transmissibility and the duration of naturally-acquired immunity, is essential in estimating the impact of vaccination programmes and screening or testing regimes. However, the complex natural history of HPV makes this difficult. We infer the viral transmissibility, rate of waning natural immunity and rates of progression and clearance of infection of 13 high-risk and 2 non-oncogenic HPV types, making use of a number of rich datasets from Sweden. Estimates of viral transmissibility, clearance of initial infection and waning immunity were derived in a Bayesian framework by fitting a susceptible-infectious-recovered-susceptible (SIRS) transmission model to age- and type-specific HPV prevalence data from both a cross-sectional study and a randomised controlled trial (RCT) of primary HPV screening. The models fitted well, but over-estimated the prevalence of four high-risk types with respect to the data. Three of these types (HPV-33, -35 and -58) are among the most closely related phylogenetically to the most prevalent HPV-16. The fourth (HPV-45) is the most closely related to HPV-18; the second most prevalent type. We suggest that this may be an indicator of cross-immunity. Rates of progression and clearance of clinical lesions were additionally estimated from longitudinal data gathered as part of the same RCT. Our estimates of progression and clearance rates are consistent with the findings of survival analysis studies and we extend the literature by estimating progression and clearance rates for non-16 and non-18 high-risk types. We anticipate that such type-specific estimates will be useful in the parameterisation of further models and in developing our understanding of HPV natural history.

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.