Testing previous model predictions against new data on human papillomavirus vaccination program outcomes

Benefits, harms and cost-effectiveness of cervical screening, triage and treatment strategies for women in the general population

In 2020, the World Health Organization (WHO) launched a strategy to eliminate cervical cancer as a public health problem. To support the strategy, the WHO published updated cervical screening guidelines in 2021. To inform this update, we used an established modeling platform, Policy1-Cervix, to evaluate the impact of seven primary screening scenarios across 78 low- and lower-middle-income countries (LMICs) for the general population of women. Assuming 70% coverage, we found that primary human papillomavirus (HPV) screening approaches were the most effective and cost-effective, reducing cervical cancer age-standardized mortality rates by 63-67% when offered every 5 years. Strategies involving triaging women before treatment (with 16/18 genotyping, cytology, visual inspection with acetic acid (VIA) or colposcopy) had close-to-similar effectiveness to HPV screening without triage and fewer pre-cancer treatments. Screening with VIA or cytology every 3 years was less effective and less cost-effective than HPV screening every 5 years. Furthermore, VIA generated more than double the number of pre-cancer treatments compared to HPV. In conclusion, primary HPV screening is the most effective, cost-effective and efficient cervical screening option in LMICs. These findings have directly informed WHO's updated cervical screening guidelines for the general population of women, which recommend primary HPV screening in a screen-and-treat or screen-triage-and-treat approach, starting from age 30 years with screening every 5 years or 10 years.

Proposal for a descriptive and differentiated presentation of the longitudinal impact of the new organized cancer screening guideline and HPV vaccination in Germany

INTRODUCTION

Since 01/01/2020, the cervical cancer screening in Germany has been carried out due to the organized early cancer diagnosis guideline (oKFE-RL). In 2007, HPV vaccination was initiated in Germany. The main goal of both initiatives is to further reduce the incidence of invasive cervical cancer. To assess the effect of the new screening strategy in a timely manner, monitoring of short-term changes need to be considered. Ideally, the effects of both prevention methods would be presented together in one model.

MATERIALS AND METHODS

Because no change in the incidence of invasive cervical cancer is initially expected, the incidence of CIN 3 is used as a surrogate parameter to assess the effects of the prevention efforts. Based on expected additional effects of vaccination and co-testing, a model-based estimation of the expected CIN 3 incidence during the evaluation of the screening program is performed using the CIN 3 incidence in the Saarland population.

MODELING RESULTS

The oKFE-RL provides for two groups: Primary cytodiagnosis continues until 35 years of age. Here, in the next few years, CIN 3 incidence will be reduced not by the oKFE-RL but by the increasing proportion of vaccinated women. In the group over 35 years, co-testing was introduced with a stringent algorithm. Due to the higher sensitivity of the HPV test, significantly more CIN 3 are detected in the first round of 3 years and thus, the CIN 3 incidence initially increases. As these CIN 3 are absent in the second round, significantly fewer CIN 3 cases will be detected then. These effects suggest a global decrease in CIN 3 incidence of 25.8% after 6 years.

CONCLUSION

Observation of the age distribution curve of CIN 3 allows both effects of prevention to be assessed in a timely manner and separately. In the future, data from epidemiologic cancer registries should be incorporated into the model to replace modeling with real data.

Surveillance systems for monitoring cervical cancer elimination efforts: Focus on HPV infection, cervical dysplasia, cervical screening and treatment

In order to achieve the global elimination of cervical cancer as a public health problem, close surveillance of progress in public health and clinical activities and outcomes across the three pillars of vaccination, screening and treatment will be required. Surveillance should ideally occur within an integrated system that is planned, funded, and regularly evaluated to ensure it is providing timely, accurate and relevant feedback for action. In this paper, we conceptualise the main public health surveillance objectives as process and outcome measures in each of the three pillars. Process measures include coverage/participation measures for vaccination, screening and treatment alongside the ongoing assessment of the quality and reach of these programs and activities. Outcome measures related to the natural history of human papillomavirus (HPV) infection include HPV infection prevalence, precursor cervical lesions and cervical cancers (including stage at diagnosis, cancer incidence and mortality). These outcome measures can be used for monitoring the effectiveness of the three core activities in the short, medium and long term to assess whether these interventions are effectively reducing their occurrence. We discuss possible methods for the surveillance of these measures in the context of country capacity, drawing from examples in Australia, the USA and in low and middle income countries.

Protocol for Compass: a randomised controlled trial of primary HPV testing versus cytology screening for cervical cancer in HPV-unvaccinated and vaccinated women aged 25-69 years living in Australia

INTRODUCTION

Australia's National Cervical Screening Program (NCSP) currently recommends 2-year cytology in women aged 18-69 years. Following a review of the NCSP prompted by the implementation of human papillomavirus (HPV) vaccination, the programme will transition in 2017 to 5-year primary HPV screening with partial genotyping for HPV16/18 in women aged 25-74 years. Compass is a sentinel experience for the renewed NCSP and the first prospectively randomised trial of primary HPV screening compared with cytology to be conducted in a population with high uptake of HPV vaccination. This protocol describes the main Compass trial, which commenced after a pilot study of ~5000 women completed recruitment.

METHODS AND ANALYSIS

Women aged 25-69 years will be randomised at a 1:2 allocation to (1) 2.5-year image-read, liquid-based cytology (LBC) screening with HPV triage of low-grade smears (active control Arm A) or (2) 5-year HPV screening with partial genotyping and referral of HPV16/18-positive women to colposcopy (intervention Arm B). Women in Arm B positive for other oncogenic HPV (not 16/18) will undergo secondary randomisation at a 1:1 allocation to either LBC or dual-stained (p16^INK4a and Ki-67) cytology testing (dual-stained cytology). The primary outcome is cumulative CIN3+ (CIN3, adenocarcinoma in situ and invasive cervical cancer) following a 5-year HPV exit testing round in both arms, in women randomised to the HPV arm versus women randomised to the LBC arm, based on an intention-to-treat analysis. The primary outcome will first be tested for non-inferiority and if declared, the primary outcome will be tested for superiority. A total of 36 300 women in birth cohorts not offered vaccination and 84 700 women in cohorts offered vaccination will be recruited, bringing the final sample size to 121 000. The trial is powered for the secondary outcome of cumulative CIN3+ in screen-negative women, adjusted for censoring after CIN2+ treatment and hysterectomy.

ETHICS AND DISSEMINATION

Approved by the Bellberry Ethics Committee (2014-11-592). Findings will be reported in peer-reviewed journals and presented at scientific meetings.

TRIAL REGISTRATION NUMBER

NCT02328872; Pre-results.

Optimal Management Strategies for Primary HPV Testing for Cervical Screening: Cost-Effectiveness Evaluation for the National Cervical Screening Program in Australia

BACKGROUND

Several countries are implementing a transition to HPV testing for cervical screening in response to the introduction of HPV vaccination and evidence indicating that HPV screening is more effective than cytology. In Australia, a 2017 transition from 2-yearly conventional cytology in 18-20 to 69 years to 5-yearly primary HPV screening in 25 to 74 years will involve partial genotyping for HPV 16/18 with direct referral to colposcopy for this higher risk group. The objective of this study was to determine the optimal management of women positive for other high-risk HPV types (not 16/18) ('OHR HPV').

METHODS

We used a dynamic model of HPV transmission, vaccination, natural history and cervical screening to determine the optimal management of women positive for OHR HPV. We assumed cytology triage testing was used to inform management in this group and that those with high-grade cytology would be referred to colposcopy and those with negative cytology would receive 12-month surveillance. For those with OHR HPV and low-grade cytology (considered to be a single low-grade category in Australia incorporating ASC-US and LSIL), we evaluated (1) the 20-year risk of invasive cervical cancer assuming this group are referred for 12-month follow-up vs. colposcopy, and compared this to the risk in women with low-grade cytology under the current program (i.e. an accepted benchmark risk for 12-month follow-up in Australia); (2) the population-level impact of the whole program, assuming this group are referred to 12-month surveillance vs. colposcopy; and (3) the cost-effectiveness of immediate colposcopy compared to 12-month follow-up. Evaluation was performed both for HPV-unvaccinated cohorts and cohorts offered vaccination (coverage ~72%).

FINDINGS

The estimated 20-year risk of cervical cancer is ≤1.0% at all ages if this group are referred to colposcopy vs. ≤1.2% if followed-up in 12 months, both of which are lower than the ≤2.6% benchmark risk in women with low-grade cytology in the current program (who are returned for 12-month follow-up). At the population level, immediate colposcopy referral provides an incremental 1-3% reduction in cervical cancer incidence and mortality compared with 12-month follow-up, but this is in the context of a predicted 24-36% reduction associated with the new HPV screening program compared to the current cytology-based program. Furthermore, immediate colposcopy substantially increases the predicted number of colposcopies, with >650 additional colposcopies required to avert each additional case of cervical cancer compared to 12-month follow-up. Compared to 12-month follow-up, immediate colposcopy has an incremental cost-effectiveness ratio (ICER) of A$104,600/LYS (95%CrI:A$100,100-109,100) in unvaccinated women and A$117,100/LYS (95%CrI:A$112,300-122,000) in cohorts offered vaccination [Indicative willingness-to-pay threshold: A$50,000/LYS].

CONCLUSIONS

In primary HPV screening programs, partial genotyping for HPV16/18 or high-grade triage cytology in OHR HPV positive women can be used to refer the highest risk group to colposcopy, but 12-month follow-up for women with OHR HPV and low-grade cytology is associated with a low risk of developing cervical cancer. Direct referral to colposcopy for this group would be associated with a substantial increase in colposcopy referrals and the associated harms, and is also cost-ineffective; thus, 12-month surveillance for women with OHR HPV and low-grade cytology provides the best balance between benefits, harms and cost-effectiveness.

Population-level impact, herd immunity, and elimination after human papillomavirus vaccination: a systematic review and meta-analysis of predictions from transmission-dynamic models

BACKGROUND

Modelling studies have been widely used to inform human papillomavirus (HPV) vaccination policy decisions; however, many models exist and it is not known whether they produce consistent predictions of population-level effectiveness and herd effects. We did a systematic review and meta-analysis of model predictions of the long-term population-level effectiveness of vaccination against HPV 16, 18, 6, and 11 infection in women and men, to examine the variability in predicted herd effects, incremental benefit of vaccinating boys, and potential for HPV-vaccine-type elimination.

METHODS

We searched MEDLINE and Embase for transmission-dynamic modelling studies published between Jan 1, 2009, and April 28, 2015, that predicted the population-level impact of vaccination on HPV 6, 11, 16, and 18 infections in high-income countries. We contacted authors to determine whether they were willing to produce new predictions for standardised scenarios. Strategies investigated were girls-only vaccination and girls and boys vaccination at age 12 years. Base-case vaccine characteristics were 100% efficacy and lifetime protection. We did sensitivity analyses by varying vaccination coverage, vaccine efficacy, and duration of protection. For all scenarios we pooled model predictions of relative reductions in HPV prevalence (RRprev) over time after vaccination and summarised results using the median and 10th and 90th percentiles (80% uncertainty intervals [UI]).

FINDINGS

16 of 19 eligible models from ten high-income countries provided predictions. Under base-case assumptions, 40% vaccination coverage and girls-only vaccination, the RRprev of HPV 16 among women and men was 0·53 (80% UI 0·46-0·68) and 0·36 (0·28-0·61), respectively, after 70 years. With 80% girls-only vaccination coverage, the RRprev of HPV 16 among women and men was 0·93 (0·90-1·00) and 0·83 (0·75-1·00), respectively. Vaccinating boys in addition to girls increased the RRprev of HPV 16 among women and men by 0·18 (0·13-0·32) and 0·35 (0·27-0·39) for 40% coverage, and 0·07 (0·00-0·10) and 0·16 (0·01-0·25) for 80% coverage, respectively. The RRprev were greater for HPV 6, 11, and 18 than for HPV 16 for all scenarios investigated. Finally at 80% coverage, most models predicted that girls and boys vaccination would eliminate HPV 6, 11, 16, and 18, with a median RRprev of 1·00 for women and men for all four HPV types. Variability in pooled findings was low, but increased with lower vaccination coverage and shorter vaccine protection (from lifetime to 20 years).

INTERPRETATION

Although HPV models differ in structure, data used for calibration, and settings, our population-level predictions were generally concordant and suggest that strong herd effects are expected from vaccinating girls only, even with coverage as low as 20%. Elimination of HPV 16, 18, 6, and 11 is possible if 80% coverage in girls and boys is reached and if high vaccine efficacy is maintained over time.

FUNDING

Canadian Institutes of Health Research.

Impact of HPV sample self-collection for underscreened women in the renewed Cervical Screening Program

OBJECTIVES

In 2017, the National Cervical Screening Program in Australia will transition to 5-yearly primary HPV screening for all women, irrespective of human papillomavirus (HPV) vaccination status. As an adjunct to the mainstream program, HPV testing on self-collected samples will be offered under practitioner supervision to all unscreened and underscreened women aged 30-74 years. We quantified how different screening decisions affect the future risk of cervical cancer.

DESIGN

Simulation of outcomes for 100 000 previously unscreened women, aged 30 years and eligible for self-collection, using a well-established model of HPV natural history and cervical screening.

MAIN OUTCOME MEASURES

Cumulative cancer diagnoses and deaths averted (compared with remaining unscreened) to age 84, number needed to treat for pre-cancer (NNT) to avert each cancer diagnosis.

RESULTS

One round of self-collected HPV screening at age 30 years would avert 908 cancer diagnoses and 364 cancer deaths in the cohort by age 84 (NNT, 5.8). Benefits would still be achieved were self-collected screening delayed to age 40 (922 fewer diagnoses; 426 fewer deaths; NNT, 3.7) or 50 (684 fewer diagnoses; 385 fewer deaths; NNT, 3.2). However, the benefits associated with joining the mainstream screening program would be substantially larger (2002, 1623 or 1091 fewer diagnoses and NNT of 4.9, 3.7 or 3.4 by joining at age 30, 40 or 50 years respectively). The relative benefits of joining the mainstream program were similar for cohorts who had been offered vaccination.

CONCLUSIONS

Offering HPV self-collection has the potential to considerably improve outcomes for unscreened and underscreened women. Nevertheless, these findings underscore the need for concerted strategies to encourage these women to join the mainstream HPV screening program.

HPV vaccination: The most pragmatic cervical cancer primary prevention strategy

The evidence that high-risk HPV infections cause cervical cancers has led to two new approaches for cervical cancer control: vaccination to prevent HPV infections, and HPV screening to detect and treat cervical precancerous lesions. Two vaccines are currently available: quadrivalent vaccine targeting oncogenic HPV types 16, 18, 6, and 11, and bivalent vaccine targeting HPV 16 and 18. Both vaccines have demonstrated remarkable immunogenicity and substantial protection against persistent infection and high-grade cervical cancer precursors caused by HPV 16 and 18 in HPV-naïve women, and have the potential to prevent 70% of cervical cancers in adequately vaccinated populations. HPV vaccination is now implemented in national programs in 62 countries, including some low- and middle-income countries. The early findings from routine national programs in high-income countries are instructive to encourage low- and middle-income countries with a high risk of cervical cancer to roll out HPV vaccination programs and to introduce resource-appropriate cervical screening programs.

Factors related to vaccine uptake by young adult women in the catch-up phase of the National HPV Vaccination Program in Australia: Results from an observational study

BACKGROUND

Australia commenced a publically-funded, National Human Papillomavirus (HPV) Vaccination Program in 2007 with a two year catch-up phase for females aged 12-26 years.

OBJECTIVE

To identify the factors associated with the uptake of the HPV vaccine (which has a recommended 3-dose schedule in Australia) by young adult women vaccinated by general practitioners and community-based programs within the catch-up phase.

METHODS

1139 women who were eligible to receive the free HPV vaccine during the catch-up period were recruited in 2008-2009 (age 20-29 years at recruitment), in New South Wales, after having a normal (negative) cervical smear result recorded on the NSW Pap Test Register. Participants completed a self-administered questionnaire providing information on vaccination status, and sociodemographic and other factors.

RESULTS

Overall, 880 (77%) women reported receiving ≥ 1 dose of the vaccine and 777 women (68%) reported receiving ≥ 2 doses. In multivariable analysis (adjusting for the period for which each woman was eligible for free HPV vaccination), uptake of ≥ 1 dose of the vaccine was significantly associated with being born in Australia (p < 0.01), being single (p = 0.02), being nulliparous (p < 0.01), living in a higher socioeconomic status area (p-trend = 0.03), living in more remote areas (p = 0.03), drinking alcohol (p < 0.01) and using hormonal contraceptives (p < 0.01). Although vaccinated women were more likely to have fewer sexual partners than unvaccinated women (p-trend = 0.02), they were also more likely to report a prior sexually transmitted infection (STI) (p = 0.03). Similar factors were associated with receiving ≥ 2 doses.

CONCLUSIONS

In this group, women living in higher socioeconomic status areas were more likely to be vaccinated against HPV in the catch-up phase of the national program. Although vaccinated women tended to have fewer sexual partners, they also reported prior STIs, which may be a marker of increased risk of prior exposure to HPV. The findings of this study reinforce the continuing need to prioritise equitable delivery of vaccination to various population subgroups.

The next steps in cervical screening

Cervical cancer is fourth most common cancer among women with four-fifths of the global burden in low- and middle-income countries (LMICs). Persistent infection with one of the high-risk types of human papillomaviruses (HPV), particularly HPV 16/18, is the central cause of cervical neoplasia. Progress in developing feasible, alternative screening methods in LMICs and HPV vaccines have further improved cervical cancer prevention prospects. While existing screening programs in high-income countries should be re-organized, in view of the downstream effects of national HPV vaccination programs, LMICs should introduce national programs to vaccinate single year cohorts of girls aged 9-13 years with two or three doses and screen 30-35-year-old women with HPV testing to pragmatically decrease their high disease burden.

Factors impacting HPV vaccination: lessons for health care professionals

HPV infection leads to significant morbidity and mortality worldwide. The HPV vaccine is currently licensed and recommended for adolescents and young adults in many countries. Nonetheless, coverage levels remain low, especially in settings using a clinic-based rather than school-based delivery model. Health care professionals (HCPs) have the potential to strongly impact HPV vaccine acceptability and uptake, yet often fail to discuss and/or strongly recommend HPV vaccination. This article reviews the myriad factors that influence HPV vaccination, focusing, in particular, on those relevant to HCP communication with patients and families. It also provides a historical framework and highlights recent evidence related to HPV vaccination that may be valuable for these conversations. Lastly, it discusses strategies targeting HCPs and their practices that may increase HPV vaccination initiation and completion rates globally.