Verification of Decision-Analytic Models for Health Economic Evaluations: An Overview.

Decision-analytic models for cost-effectiveness analysis are developed in a variety of software packages where the accuracy of the computer code is seldom verified. Although modeling guidelines recommend using state-of-the-art quality assurance and control methods for software engineering to verify models, the fields of pharmacoeconomics and health technology assessment (HTA) have yet to establish and adopt guidance on how to verify health and economic models. The objective of this paper is to introduce to our field the variety of methods the software engineering field uses to verify that software performs as expected. We identify how many of these methods can be incorporated in the development process of decision-analytic models in order to reduce errors and increase transparency. Given the breadth of methods used in software engineering, we recommend a more in-depth initiative to be undertaken (e.g., by an ISPOR-SMDM Task Force) to define the best practices for model verification in our field and to accelerate adoption. Establishing a general guidance for verifying models will benefit the pharmacoeconomics and HTA communities by increasing accuracy of computer programming, transparency, accessibility, sharing, understandability, and trust of models.

Modeling the durability of ZOSTAVAX® vaccine efficacy in people ≥60 years of age.

Since 2006, the vaccine, ZOSTAVAX(®), has been licensed to prevent herpes zoster. Only limited clinical follow-up data are available to evaluate duration of protection, an important consideration when developing HZ vaccination policy recommendations. Four Poisson regression models were developed based on an integrated analysis of data from the Shingles Prevention Study and its Short Term Persistence extension to estimate the effects of years-since-vaccination and chronological-age on vaccine efficacy among people ≥60 years old. The models included number of HZ cases parsed into categories by chronological-age and time-since-vaccination as the dependent variable with different explanatory variables in each model. In all models, the interaction between vaccine-group and chronological-age was statistically significant indicating that vaccine efficacy decreases with the expected effects of advancing age but the interaction between vaccine-group and time-since-vaccination was not statistically significant indicating that much of the reduction in vaccine efficacy over time-since-vaccination can be explained by increasing age.

Cost-effectiveness of pneumococcal vaccines for adults in the United States.

INTRODUCTION: In 2012, the Advisory Committee on Immunization Practices (ACIP) revised recommendations for adult pneumococcal vaccination to include a sequential regimen of 13-valent pneumococcal conjugate vaccine (PCV13) followed by 23-valent pneumococcal polysaccharide vaccine (PPSV23) for certain high-risk adults with immunocompromising conditions. This study, from a payer perspective, examined: (1) the cost-effectiveness of the new 2012 ACIP vaccine policy recommendation relative to the 1997 ACIP recommendation; (2) the cost-effectiveness of potential future pneumococcal vaccination policies; and (3) key assumptions that influence study results. METHODS: A static cohort model that incorporated costs, health outcomes, and quality-adjusted life-year (QALY) losses associated with invasive pneumococcal disease and non-bacteremic pneumococcal pneumonia (NBPP) was developed to evaluate seven pneumococcal vaccination strategies for a 50-year-old adult cohort over a 50-year period using incremental cost-effectiveness ratios (ICERs). RESULTS: For objective 1, the 2012 ACIP recommendation is the more economically efficient strategy (ICER was $25,841 per QALY gained vs. no vaccination). For objective 2, the most efficient vaccination policy would be to maintain the 2012 recommendation for PPSV23 for healthy and immunocompetent adults with comorbidities, and to modify the recommendation for adults with immunocompromising conditions by replacing PPSV23 with a sequential regimen of PCV13 and PPSV23 at age 65 (ICER was $23,416 per QALY gained vs. no vaccination). For objective 3, cost-effectiveness ratios for alternative pneumococcal vaccine policies were highly influenced by assumptions used for vaccine effectiveness against NBPP and accounting for the herd protection effects of pediatric PCV13 vaccination on adult pneumococcal disease. CONCLUSION: Modifying the 2012 recommendation to include an additional dose of PCV13 at age 65, followed by PPSV23, for adults with immunocompromising conditions appears to be a cost-effective vaccine policy. Given the uncertainty in the available data and the absence of key influential data, comprehensive sensitivity analyses should be conducted by policy-makers when evaluating new adult pneumococcal vaccine strategies.

Targeting human papillomavirus to reduce the burden of cervical, vulvar and vaginal cancer and pre-invasive neoplasia: establishing the baseline for surveillance.

BACKGROUND: Infection with high-risk human papillomavirus (HPV) is causally related to cervical, vulvar and vaginal pre-invasive neoplasias and cancers. Highly effective vaccines against HPV types 16/18 have been available since 2006, and are currently used in many countries in combination with cervical cancer screening to control the burden of cervical cancer. We estimated the overall and age-specific incidence rate (IR) of cervical, vulvar and vaginal cancer and pre-invasive neoplasia in Denmark, Iceland, Norway and Sweden in 2004-2006, prior to the availability of HPV vaccines, in order to establish a baseline for surveillance. We also estimated the population attributable fraction to determine roughly the expected effect of HPV16/18 vaccination on the incidence of these diseases. METHODS: Information on incident cervical, vulvar and vaginal cancers and high-grade pre-invasive neoplasias was obtained from high-quality national population-based registries. A literature review was conducted to define the fraction of these lesions attributable to HPV16/18, i.e., those that could be prevented by HPV vaccination. RESULTS: Among the four countries, the age-standardised IR/105 of cervical, vaginal and vulvar cancer ranged from 8.4-13.8, 1.3-3.1 and 0.2-0.6, respectively. The risk for cervical cancer was highest in women aged 30-39, while vulvar and vaginal cancers were most common in women aged 70+. Age-standardised IR/105 of cervical, vulvar and vaginal pre-invasive neoplasia ranged between 138.8-183.2, 2.5-8.8 and 0.5-1.3, respectively. Women aged 20-29 had the highest risk for cervical pre-invasive neoplasia, while vulvar and vaginal pre-invasive neoplasia peaked in women aged 40-49 and 60-69, respectively. Over 50% of the observed 47,820 incident invasive and pre-invasive cancer cases in 2004-2006 can be attributed to HPV16/18. CONCLUSION: In the four countries, vaccination against HPV 16/18 could prevent approximately 8500 cases of gynecological cancer and pre-cancer annually. Population-based cancer and vaccination registries are essential to assess the predicted public health effects of HPV vaccination.

The Cost-Effectiveness Analysis of a Quadrivalent Human Papillomavirus Vaccine (6/11/16/18) for Females in Japan.

OBJECTIVE: We assessed the epidemiological and economic impact of a quadrivalent human papillomavirus (HPV) (6/11/16/18) vaccine for females in preventing cervical cancer, cervical intraepithelial neoplasia grades 2 and 3 (CIN 2/3), cervical intraepithelial neoplasia grade 1 (CIN 1), and genital warts in Japan by using a transmission dynamic model. METHODS: A published mathematical model of the transmission dynamics of HPV infection and disease was adapted for Japan. Model inputs were used from Japan or the Asia/Pacific region when available; otherwise, the default values in the original model were used. The transmission dynamic model was used to assess the epidemiological and economic impact of a quadrivalent HPV (6/11/16/18) vaccine for females in preventing cervical cancer, CIN 2/3, CIN 1, and genital warts in Japan.Maintaining current cervical cancer screening practices, we evaluated two strategies: routine vaccination of females by age 12 years (S1), and S1 combined with a temporary (5 years) female catch-up program for age 12 to 24 years (S2). The vaccine coverage rate was 80% for the routine and 50% for the catch-up vaccination programs. RESULTS: Compared with no vaccination, both vaccination strategies significantly reduced the incidence of HPV 6/11/16/18-related disease. The most effective strategy was S2. By using this strategy over 100 years in the Japanese population, the estimated cumulative percentage reduction in incident HPV 6/11/16/18-related genital warts-female, genital warts-male, cervical CIN 1, CIN 2/3, and cervical cancer cases was 90% (2,113,723 cases), 86% (2,082,637 cases), 72% (263,406 cases), 71% (1,328,366 cases), and 58% (323,145 cases), respectively. The cost-effectiveness ratios were JPY 1,244,000, and JPY 1,205,800 per quality-adjusted life-year gained for S1 and S2 compared with no vaccination, respectively, over a time horizon of 100 years. CONCLUSION: We conclude that a quadrivalent HPV vaccination program for females can reduce the incidence of cervical cancer, CIN, and genital warts in Japan at a cost-per-quality-adjusted life-year ratio within the range defined as cost-effective.

Cost-effectiveness of stockpiling 23-valent pneumococcal polysaccharide vaccine to prevent secondary pneumococcal infections among a high-risk population in the United States during an influenza pandemic.

BACKGROUND: Secondary bacterial infections (especially pneumococcal infections) were a major cause of death during prior influenza pandemics. One strategy to prevent pneumococcal infections in adults during a future pandemic is to stockpile 23-valent pneumococcal polysaccharide vaccine (PPSV23). Stockpiling a pneumococcal vaccine can ensure that it is available when needed most-that is, at the onset of a pandemic. OBJECTIVE: The purpose of this article was to project the health and economic impact of stockpiling PPSV23 to prevent secondary pneumococcal infections among high-risk adults aged 18 to 64 years during an influenza pandemic within the United States. METHODS: A cost-effectiveness model was developed to evaluate the health and economic effects of stockpiling PPSV23 versus not stockpiling this vaccine for preventing secondary pneumococcal infections among 20 million high-risk US adults aged 18 to 64 years during an influenza pandemic. The model was used to project the number of pneumococcal cases, hospitalizations, deaths, and days of work loss averted. Three health outcomes (deaths, hospitalizations, and outpatient care) were estimated from secondary pneumococcal infections. To assess the overall effectiveness of the different strategies, the quality-adjusted life-year (QALY) was used as a measure of these 3 health outcomes. The results are presented for 3 scenarios based on the pandemic severity and anticipated prepandemic influenza vaccine availability: base case, more-severe case, and less-severe case. RESULTS: In the base-case scenario, vaccinating 20 million high-risk adults with PPSV23 avoided 2858 deaths, 878 hospitalizations, 41,881 pneumococcal pneumonia cases, and 232,891 days of work loss during a pandemic. Under the more-severe case scenario, vaccination avoided 21,921 deaths, 10,280 hospitalizations, 70,345 pneumococcal cases, and approximately 1.12 million days of work loss. Under the less-severe case scenario, pneumococcal vaccination avoided 715 deaths, 219 hospitalizations, 10,470 pneumococcal cases, and 58,235 days of work loss. The incremental cost-effectiveness ratio for stockpiling PPSV23 versus no stockpiling for the base-case and less-severe case scenarios was $39,946 and $198,653 per QALY, respectively. For the more-severe case scenario, stockpiling PPSV23 was cost saving. Probabilistic sensitivity analyses found that the range of incremental cost-effectiveness ratio values was broad due to the large uncertainty regarding the timing and impact of the next pandemic. In addition, the shelf life of PPSV23 and stockpile management substantially influenced the cost-effectiveness ratio. CONCLUSIONS: For severe pandemics or pandemics in which prepandemic influenza vaccine is unavailable, stockpiling of PPSV23 can be a cost-effective strategy for reducing the health and economic burden associated with secondary pneumococcal infections in a high-risk US population. However, for a mildly severe pandemic in which prepandemic influenza vaccine is available, stockpiling of PPSV23 may not be cost-effective.

Impact of vaccinating boys and men against HPV in the United States.

We assessed the public health impact and value of vaccinating boys and men with the quadrivalent HPV vaccine in the United States. We used mathematical population models, accounting for both the direct and indirect protective effects of vaccination. Inputs for the models were obtained from public data sources, published literature, and analyses of clinical trial data. Compared with a program of vaccinating girls and women only, including boys and men 9-26 years of age would further decrease the cumulative mean number of genital wart cases, cervical intraepithelial neoplasia 2/3 cases, cancer cases, and cancer deaths by 5,146,000, 708,000, 116,000, and 40,000, respectively, within 100 years. The mean cost-effectiveness ratio (2008 US $) of this strategy was $25,700 (range: 13,600-48,800) per QALY gained if vaccination protects against all HPV 6/11/16/18-associated diseases, and $69,000 (range: 37,700-152,300)/QALY if it only protects against diseases currently in the vaccine indication. Vaccinating boys and men age 9-26 against all HPV 6/11/16/18-associated diseases provides substantial public health benefits and is cost-effective at commonly cited thresholds.

The cost effectiveness of a quadrivalent human papillomavirus vaccine (6/11/16/18) in Hungary.

OBJECTIVE: A transmission dynamic model was used to assess the epidemiological and economic impact of a quadrivalent human papillomavirus (HPV) (6/11/16/18) vaccine in preventing cervical cancer, cervical intraepithelial neoplasia grades 2 and 3 (CIN 2/3), CIN 1 and genital warts in Hungary. METHODS: The routine vaccination of 12-year-old girls and the routine vaccination of 12-year-old girls plus a temporary catch-up programme for girls and women aged 12-24 years was evaluated. RESULTS: The model projected that at year 100, both strategies could reduce the incidence of HPV 6/11/16/18-related cervical cancer, CIN 2/3, CIN 1 and genital warts cases among Hungarian women by 90%, 90%, 85% and 93%, respectively. Twenty-five years after the introduction of HPV vaccination in the population, routine vaccination of girls by the age of 12 reduced the cumulative number of cases of cervical cancer, CIN 2/3, CIN 1 and genital warts by 685, 13,473, 3,423 and 163,987, respectively. The incremental cost-effectiveness ratios of the two vaccination strategies were €9,577 and €10,646 per quality-adjusted life-year (QALY) gained over a time horizon of 100 years. KEY LIMITATIONS: The model did not account for the health and economic impact of other HPV diseases which may result from HPV 16, 18, 6, and 11 infections such as vaginal, vulvar, penile, anal and head-neck cancers, and recurrent respiratory papillomatosis. Epidemiological data from Hungary on these other HPV diseases as well genital warts are needed. CONCLUSION: A quadrivalent HPV vaccination programme can reduce the incidence of cervical cancer, CIN and genital warts in Hungary at a cost-per-QALY ratio within the range defined as cost effective.

Epidemiologic natural history and clinical management of Human Papillomavirus (HPV) Disease: a critical and systematic review of the literature in the development of an HPV dynamic transmission model.

BACKGROUND: Natural history models of human papillomavirus (HPV) infection and disease have been used in a number of policy evaluations of technologies to prevent and screen for HPV disease (e.g., cervical cancer, anogenital warts), sometimes with wide variation in values for epidemiologic and clinical inputs. The objectives of this study are to: (1) Provide an updated critical and systematic review of the evidence base to support epidemiologic and clinical modeling of key HPV disease-related parameters in the context of an HPV multi-type disease transmission model which we have applied within a U.S. population context; (2) Identify areas where additional studies are particularly needed. METHODS: Consistent with our and other prior HPV natural history models, the literature review was confined to cervical disease and genital warts. Between October 2005 and January 2006, data were gathered from the published English language medical literature through a search of the PubMed database and references were examined from prior HPV natural history models and review papers. Study design and data quality from individual studies were compared and analyses meeting pre-defined criteria were selected. RESULTS: Published data meeting review eligibility criteria were most plentiful for natural history parameters relating to the progression and regression of cervical intraepithelial neoplasia (CIN) without HPV typing, and data concerning the natural history of HPV disease due to specific HPV types were often lacking. Epidemiologic evidence to support age-dependency in the risk of progression and regression of HPV disease was found to be weak, and an alternative hypothesis concerning the time-dependence of transition rates is explored. No data were found on the duration of immunity following HPV infection. In the area of clinical management, data were observed to be lacking on the proportion of clinically manifest anogenital warts that are treated and the proportion of cervical cancer cases that become symptomatic by stage. CONCLUSION: Knowledge of the natural history of HPV disease has been considerably enhanced over the past two decades, through the publication of an increasing number of relevant studies. However, considerable opportunity remains for advancing our understanding of HPV natural history and the quality of associated models, particularly with respect to examining HPV age- and type-specific outcomes, and acquired immunity following infection.

Age-based programs for vaccination against HPV.

BACKGROUND: The risk of infection with human papillomavirus (HPV) increases with age. Answering the question of which age groups are appropriate to target for catch-up vaccination with the newly licensed quadrivalent HPV vaccine (types 6/11/16/18) will be important for developing vaccine policy recommendations. OBJECTIVES: To assess the value of varying female HPV vaccination strategies by specific age groups of a catch-up program in the United States. METHODS: The authors used previously published mathematical population dynamic model and cost-utility analysis to evaluate the public health impact and cost-effectiveness of alternative quadrivalent HPV (6/11/16/18) vaccination strategies. The model simulates heterosexual transmission of HPV infection and occurrence of cervical intraepithelial neoplasia (CIN), cervical cancer, and external genital warts in an age-structured population stratified by sex and sexual activity groups. The cost-utility analysis estimates the cost of vaccination, screening, diagnosis, and treatment of HPV diseases, and quality-adjusted survival. RESULTS: Compared with the current screening practices, vaccinating girls and women ages 12 to 24 years was the most effective strategy, reducing the number of HPV6/11/16/18-related genital warts, CIN grades 2 and 3, and cervical cancer cases among women in the next 25 years by 3,049,285, 1,399,935, and 30,021; respectively. The incremental cost-effectiveness ratio of this strategy when compared with vaccinating girls and women ages 12 to 19 years was $10,986 per quality-adjusted life-year gained. CONCLUSION;: Relative to other commonly accepted health-care programs, vaccinating girls and women ages 12 to 24 years appears cost-effective.

The cost-effectiveness of a quadrivalent human papillomavirus vaccine in Taiwan.

BACKGROUND: A quadrivalent human papillomavirus (HPV 6/11/16/18) vaccine has recently received regulatory approval in Taiwan for the prevention of cervical carcinoma, high-grade cervical dysplasia (cervical intraepithelial neoplasia 2/3 [CIN 2/3]), low-grade cervical dysplasia (CIN 1), high-grade vulvar and vaginal dysplasia, and external genital warts. OBJECTIVE: To examine the potential long-term epidemiologic and economic consequences of a quadrivalent HPV (6/11/16/18) vaccination program in Taiwan. METHODS: A transmission dynamic model was used to estimate the long-term epidemiologic and economic consequences of quadrivalent HPV vaccination. Two vaccination strategies were evaluated in conjunction with current cervical cancer screening: 1) vaccination of 12-year-old girls and 2) vaccination of 12-year-old girls with a temporary 5-year catch-up vaccination of females aged 12-24 years (catch-up). RESULTS: From an epidemiologic perspective, both vaccination strategies reduce the overall incidence of HPV 16/18-related cervical cancer relative to no vaccination by 91% during year 100 following vaccine introduction. Likewise, both vaccination strategies reduce the incidence of CIN 2/3, CIN 1, and genital warts by approximately 90%, 86%, and 94%, respectively, at this time point. However, the catch-up program consistently achieves greater benefit earlier than the 12-year-old program. The catch-up strategy is both more effective and efficient than the strategy that vaccinates 12-year-old girls only, with an incremental cost-effectiveness ratio of New Taiwan dollars (NT$) 410,477 per quality-adjusted life-year gained. CONCLUSIONS: The results from this model suggest that in Taiwan, prophylactic HPV 6/11/16/18 vaccination of females can: 1) substantially reduce genital warts, CIN, and cervical cancer; 2) improve quality of life and survival; and 3) be cost-effective when implemented as a vaccination strategy that includes a temporary catch-up program.

A multi-type HPV transmission model.

A prophylactic quadrivalent (types 6/11/16/18) vaccine against oncogenic and warts-causing genital Human papillomavirus (HPV) types was approved by the US Food and Drug Administration in 2006. This paper presents a nonlinear, deterministic, age-structured, mathematical model of the transmission dynamics of HPV and disease occurrence in a US population stratified by gender and sexual activity group. The model can assess both the epidemiologic consequences and cost effectiveness of alternative vaccination strategies in a setting of organized cervical cancer screening in the United States. Inputs for the model were obtained from public data sources, published literature, and analyses of clinical trial data. The results suggest that a prophylactic quadrivalent HPV vaccine can: (i) substantially reduce the incidence of disease, (ii) increase survival among females, (iii) improve quality of life for both males and females, (iv) be cost-effective when administered to females age 12-24 years, and (v) be cost-effective when implemented as a strategy that combines vaccination of both females and males before age 12 vaccination with a 12 to 24 years of age catch-up vaccination program.

Structural differences among cost-effectiveness models of human papillomavirus vaccines.

In this article we compare previously published cost-effectiveness studies of human papillomavirus (HPV) vaccines along a defined subset of key model structural assumptions relating to HPV infection and disease, cervical cancer screening and HPV vaccination. For each structural aspect examined, we summarize assumptions from each study, provide a critical review and discuss the impact upon results. Considerable variation was observed across HPV vaccine cost-effectiveness models in a number of influential assumptions. Holding constant factors for which current data are lacking, the combined impact of assumptions made for the remaining parameters examined would appear to tend toward underestimation of the cost-effectiveness of HPV vaccination within existing studies. However, uncertainty concerning parameters, such as the duration of vaccine protection and acquired immunity following HPV infection, and the relationship between age and HPV virulence, complicates precise estimation of the cost-effectiveness of HPV vaccination and rigorous evaluation of the validity of existing modeling results.

Reductions in human papillomavirus-disease resource use and costs with quadrivalent human papillomavirus (types 6, 11, 16, and 18) recombinant vaccination: the FUTURE Study Economic Evaluation.

OBJECTIVE: To examine the short-term impact of quadrivalent human papillomavirus (HPV) (types 6/11/16/18) recombinant vaccination upon HPV disease-related health-care resource utilization and costs among young women. METHODS: We analyzed data from a randomized clinical trial comparing quadrivalent vaccination to placebo, among women (N = 7861) primarily 16 to 23 years of age at enrollment. HPV disease episodes, health-care resource utilization and costs associated with cervical, vaginal, and vulvar precancers, and anogenital warts were analyzed over a period of 2.5 years among women, regardless of baseline HPV status. RESULTS: Overall, there was a 25.9% (P < 0.001) reduction in total HPV disease-related health-care costs among women receiving vaccine versus placebo (absolute reduction $3939 per 100 trial enrollees). We observed similar overall reductions in HPV-disease episodes and resource utilization. There was a statistically significant reduction in HPV 6/11-related disease episode costs of 65.1% ($1837 per 100), and a reduction of 51.4% ($1781 per 100) in HPV 16/18-related episode costs. CONCLUSIONS: Quadrivalent HPV vaccination can reduce HPV disease events, resource use and costs when administered to a broad population of young women 16 to 23 years of age. Prevention of HPV types 6 and 11 yielded similar value in terms of HPV disease cost offsets, compared to protection against HPV 16 and 18, during the years initially after vaccination. Over the short-term, costs of vaccination exceed cost offsets associated with prevention of HPV disease; however, quadrivalent HPV vaccination has previously been shown to be cost-effective in the longer term, when fully accounting for health benefits and cost offsets.

Assessment of the cost-effectiveness of a quadrivalent HPV vaccine in Norway using a dynamic transmission model.

To assess the epidemiological and economic impact of alternative quadrivalent human papillomavirus (HPV) vaccine strategies in Norway, we adapted a previously published dynamic transmission model. Vaccination of girls and women aged 12-24 years reduced the incidence of HPV 6/11/16/18-related genital warts, cervical intraepithelial neoplasia and cervical cancer by 94, 92 and 92% by year 100, respectively. The cost-effectiveness ratio for this strategy when compared with vaccinating girls before the age of 12 years only was 63,294 Norwegian kroner (euro8272) per QALY gained. Based on this model and assumptions, implementation of a quadrivalent HPV vaccine national program in Norway could reduce the incidence of cervical cancer, cervical intraepithelial neoplasia and genital warts at a cost-effectiveness ratio within the range accepted as cost effective.

Cost-effectiveness of quadrivalent human papillomavirus (HPV) vaccination in Mexico: a transmission dynamic model-based evaluation.

We examined the potential health outcomes and cost-effectiveness of quadrivalent human papillomavirus (HPV) 6/11/16/18 vaccination strategies in the Mexican population using a multi-HPV type dynamic transmission model. Assuming similar cervical screening practices, with or without vaccination, we examined the incremental cost-effectiveness of vaccination strategies for 12 year-old females, with or without male vaccination, and temporary age 12-24 catch-up vaccination for females or both sexes. The most effective strategy therein was vaccination of 12-year-olds, plus a temporary 12-24-year-old catch-up program covering both sexes; whereby HPV 6/11/16/18-related cervical cancer, high-grade cervical precancer, and genital wart incidence was reduced by 84-98% during year 50 following vaccine introduction. Incremental cost-effectiveness ratios in the primary analyses ranged from approximately 3000 dollars (U.S.) per quality-adjusted life year (QALY) gained for female vaccination strategies to approximately 16000 dollars /QALY for adding male vaccination with catch-up.

Progression and regression of incident cervical HPV 6, 11, 16 and 18 infections in young women.

BACKGROUND: We describe type-specific progression, regression and persistence of incident human papillomavirus (HPV)-6-11-16 and -18 infections, along with type distribution in cervical intra-epithelial neoplasia (CIN) lesions. METHODS: The study population consisted of 16-23 year-old women undergoing Pap testing and cervical swab polymerase chain reaction testing for HPV DNA at approximate 6 month intervals for up to 4 years in the placebo arm of a clinical trial of an HPV 16-vaccine. HPV types in incident infections were correlated with types in lesion biopsy specimens. RESULTS: 56.7% of CIN-1 and nearly one-third of CIN-2/3 lesions following incident HPV-6-11-16 or -18 infections did not correlate with the incident infection HPV type. Cumulative 36-month progression rates to CIN-2/3 testing positive for the relevant HPV type were highest for HPV-16 infections (16.5%), followed by HPV-18 (8.2%). Overall, 26.0% of CIN-1, 50.0% of CIN-2 and 70.6% of CIN-3 biopsies tested positive for HPV-6-11-16-18 infections. CONCLUSION: Women with a given HPV type may often be co-infected or subsequently infected with other types which may lead to subsequent cervical lesions. This issue has been addressed in this study reporting data for the natural history of HPV-6-11-16 and -18 infections and is a relevant consideration in designing future studies to evaluate the incidence/risk of CIN following other type-specific HPV infections.

Incidence and duration of cervical human papillomavirus 6, 11, 16, and 18 infections in young women: an evaluation from multiple analytic perspectives.

OBJECTIVE: To estimate the incidence and duration of cervical human papillomavirus (HPV)-6, HPV-11, HPV-16, and HPV-18 infections in a population of young American women. METHODS: The study population consisted of U.S. women who at baseline were 16 to 23 years of age, reported zero to five lifetime sexual partners, never having been pregnant, and never having had a prior abnormal Papanicolaou test and were enrolled in the placebo arm of a randomized multicenter clinical trial of a HPV-16 L1 virus-like particle vaccine. Women underwent type-specific endocervical/ectocervical swab HPV DNA testing at approximately 6-month intervals for up to 48 months of follow-up. To contribute person-time in the analyses of type-specific HPV incidence, a woman must have had at least three satisfactory swab specimens available and been negative for the relevant HPV type (HPV-6, HPV-11, HPV-16, or HPV-18) on her first two trial swabs. The duration of incident HPV infections was estimated using Kaplan-Meier survival analysis methods. RESULTS: Person-years of exposure ranged by type-specific analysis from 2,645 to 3,188, with an incidence rate per 100 person-years of 3.6 for HPV-6, 0.4 for HPV-11, 5.4 for HPV-16, and 2.1 for HPV-18. With censoring at the time of treatment for cervical intraepithelial neoplasia, where done, the mean duration of incident infections was 9.3, 8.4, 18.2, and 16.4 months, respectively, for HPV-6 (n = 103), HPV-11 (n = 13), HPV-16 (n = 142), and HPV-18 (n = 62). When the duration of HPV infections was truncated at the time of cervical intraepithelial neoplasia detection (any grade), where applicable, mean duration figures were 8.4, 8.1, 14.0, and 15.1 months for HPV-6, HPV-11, HPV-16, and HPV-18 infections, respectively. CONCLUSIONS: Previous studies of the mean duration of cervical HPV infection have been based on prevalent infections and/or featured relatively short duration of follow-up. This study tested women for HPV infection over a period of up to 48 months and observed a mean duration of incident HPV-16/HPV-18 infections approximately twice that of HPV-6/HPV-11.