Preventive medicine
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Preventive medicine · Mar 2021
A proposed new generation of evidence-based microsimulation models to inform global control of cervical cancer.
Health decision models are the only available tools designed to consider the lifetime natural history of human papillomavirus (HPV) infection and pathogenesis of cervical cancer, and the estimated long-term impact of preventive interventions. Yet health decision modeling results are often considered a lesser form of scientific evidence due to the inherent needs to rely on imperfect data and make numerous assumptions and extrapolations regarding complex processes. We propose a new health decision modeling framework that de-emphasizes cytologic-colposcopic-histologic diagnoses due to their subjectivity and lack of reproducibility, relying instead on HPV type and duration of infection as the major determinants of subsequent transition probabilities. ⋯ Evidence for this variability in host response to HPV infections can be inferred from HPV prevalence patterns in different regions across the lifespan, and might be linked to different average population levels of immunologic control of HPV infections. By prioritizing direct estimation of model transition probabilities from longitudinal data (and limiting reliance on model-fitting techniques that may propagate error when applied to multiple transitions), we aim to reduce the number of assumptions for greater transparency and reliability. We propose this new microsimulation model for critique and discussion, hoping to contribute to models that maximally inform efficient strategies towards global cervical cancer elimination.
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Achieving the World Health Organisation (WHO) cervical cancer elimination target of fewer than four new cases per 100,000 woman-years requires scaling up HPV vaccination of girls, cervical screening, and pre-cancer and cancer treatment. We reviewed data from four high-income colonised countries (Australia, Canada, Aotearoa New Zealand (NZ), and the United States (US)) to identify how each is currently performing compared to the cervical cancer incidence elimination and triple-intervention targets, nationally and in Indigenous women. We also summarise barriers and enablers to meeting targets for Indigenous women. ⋯ Large inequities in cervical cancer currently exist for Indigenous peoples in Australia, Canada, New Zealand and the US, and elimination is not on track for all women in these countries. Current data gaps hinder improvements. These countries must urgently address their systemic failure to care and provide health care for Indigenous women.
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Preventive medicine · Mar 2021
HPV vaccination introduction worldwide and WHO and UNICEF estimates of national HPV immunization coverage 2010-2019.
WHO/UNICEF estimates for HPV vaccination coverage from 2010 to 2019 are analyzed against the backdrop of the 90% coverage target for HPV vaccination by 2030 set in the recently approved global strategy for cervical cancer elimination as a public health problem. As of June 2020, 107 (55%) of the 194 WHO Member States have introduced HPV vaccination. The Americas and Europe are by far the WHO regions with the most introductions, 85% and 77% of their countries having already introduced respectively. ⋯ When expressed as world population coverage (i.e., weighted by population size), global coverage of the final HPV dose for 2019 is estimated at 15%. There is a long way to go to meet the 2030 elimination target of 90%. In the post-COVID era attention should be paid to maintain the pace of introductions, specially ensuring the most populous countries introduce, and further improving program performance globally.
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Preventive medicine · Mar 2021
Impact and cost-effectiveness of strategies to accelerate cervical cancer elimination: A model-based analysis.
Following the global call for action by the World Health Organization to eliminate cervical cancer (CC), we evaluated how each CC policy decision in Norway influenced the timing of CC elimination, and whether introducing nonavalent human papillomavirus (HPV) vaccine would accelerate elimination timing and be cost-effective. We used a multi-modeling approach that captured HPV transmission and cervical carcinogenesis to estimate the CC incidence associated with six past and future CC prevention policy decisions compared with a pre-vaccination scenario involving 3-yearly cytology-based screening. Scenarios examined the introduction of routine HPV vaccination of 12-year-old girls with quadrivalent vaccine in 2009, a temporary catch-up program for females aged up to 26 years in 2016-2018 with bivalent vaccine, the universal switch to bivalent vaccine in 2017, expansion to include 12-year-old boys in 2018, the switch from cytology- to HPV-based screening for women aged 34-69 in 2020, and the potential switch to nonavalent vaccine in 2021. ⋯ Cumulatively, subsequent policy decisions accelerated elimination to 2039. According to our modeling assumptions, switching to the nonavalent vaccine would not be considered 'good value for money' at relevant cost-effectiveness thresholds in Norway unless the incremental cost was $19 per dose or less (range: $17-24) compared to the bivalent vaccine. CC control policies implemented over the last decade in Norway may have accelerated the timeframe to elimination by more than 17 years and prevented over 23,800 cases by 2110.
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Preventive medicine · Mar 2021
Monitoring HPV vaccine impact on cervical disease: Status and future directions for the era of cervical cancer elimination.
Post-licensure monitoring of the impact of HPV vaccines is critical to track the progress being made toward cervical cancer elimination and to identify areas where further progress can accelerate the achievement of this important public health goal. Over the past decade, a large body of evidence has revealed convincing benefits of HPV vaccination in preventing cervical infections and precancers at the individual-level (i.e., direct effectiveness) as well as in reducing the population-level burden of disease (i.e., overall effectiveness). ⋯ Thus, monitoring the direct and overall effectiveness for cervical cancer is an urgent research priority. In this article, we summarize what is known about the effectiveness of HPV vaccines on precancerous outcomes, and we highlight considerations for continuing these important public health activities going forward to monitor progress toward cervical cancer elimination.