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Impacts of human papillomavirus vaccination for different populations: A modeling study.

ABSTRACT: International variations in the prevalence of HPV infection derive from differences in sexual behaviors, which are also a key factor of the basic reproductive number (R0 ) of HPV infection in different populations. R0 affects the strength of herd protection and hence the impact of a vaccination program. Similar vaccination programs may therefore generate different levels of impact depending upon the population's pre-vaccination HPV prevalence. We used IARC's transmission model to estimate (i) the overall effectiveness of vaccination versus no vaccination in women aged 15-34 years measured as percent prevalence reduction (%PR) of HPV16 and (ii) the corresponding herd protection in populations with gender-equal or traditional sexual behavior and with different levels of sexual activity, corresponding to pre-vaccination HPV16 prevalence from 1 to 8% as observed worldwide. Between populations with different levels of gender-equal sexual activity, the highest difference in %PR under girls-only vaccination is observed at 40% coverage (91%PR vs. 48%PR for 1% and 8% pre-vaccination prevalence, respectively). HPV16 elimination is obtained with 55 and 97% coverage, respectively. To achieve desirable levels of HPV16 prevalence after vaccination, different levels of coverage are required in populations with different levels of pre-vaccination HPV16 prevalence, for example, in populations with gender-equal sexual behavior a decrease to 1/1000 HPV16 from pre-vaccination prevalence of 1 and 8% would require coverages of 37 and 96%, respectively. In traditional populations, corresponding coverages would need to be 28 and 93%, respectively. In conclusion, pre-vaccination HPV prevalence strongly influences herd immunity and helps predict the overall effectiveness of HPV vaccination.

SUBMITTER: Baussano I

PROVIDER: S-EPMC6099330 | biostudies-literature | 2018 Sep

REPOSITORIES: biostudies-literature

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Impacts of human papillomavirus vaccination for different populations: A modeling study.

Baussano Iacopo I Lazzarato Fulvio F Ronco Guglielmo G Franceschi Silvia S

International journal of cancer 20180416 5

International variations in the prevalence of HPV infection derive from differences in sexual behaviors, which are also a key factor of the basic reproductive number (R<sub>0</sub> ) of HPV infection in different populations. R<sub>0</sub> affects the strength of herd protection and hence the impact of a vaccination program. Similar vaccination programs may therefore generate different levels of impact depending upon the population's pre-vaccination HPV prevalence. We used IARC's transmission mo ...[more]

PMID: 29603224

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Project description:ImportanceCervical cancer screening is a lifesaving intervention, with an array of approaches, including liquid-based cytology (LBC), molecular testing for human papillomavirus (HPV) infection, and combinations via parallel cotesting or sequential triage. Maximizing screening efficacy while minimizing overtreatment is vital, especially when considering how the HPV vaccine will affect the interpretation of results.ObjectivesTo estimate the likely outcomes of different screening modalities and to model how the increasing uptake of the HPV vaccine could affect the interpretation of screening results.Design, setting, and participantsThis decision analytic model established a simple Markov model to compare the outcomes of different cervical cancer screening modalities on a simulated population of women (aged ≥25 years), considering different levels of HPV vaccination.Main outcomes and measuresThe number of cases of cervical intraepithelial neoplasia (CIN) grade 2 and 3 detected and missed, the number of false positives, and the number of tests required to achieve a given level of accuracy. Positive and negative predictive values of different modalities were simulated under varying levels of HPV vaccination and therefore HPV prevalence.ResultsIn a simulated population of 1000 women aged 25 years and older with an HPV prevalence of 2%, HPV-based modalities outperformed LBC-based approaches, detecting 19% more true positives (HPV test sensitivity, 89.9% [95% CI, 88.6%-91.1%]; LBC test sensitivity, 75.5% [95% CI, 66.6%-82.7%]). While cotesting markedly reduced missed cases, detecting 29% more true positives than LBC alone (19.5 [95% CI, 19.3-19.7] per 1000 women screened vs 15.1 [95% CI, 13.3-16.5] per 1000 women screened), it unacceptably increased excess colposcopy referral by 94% (184.4 [95% CI, 181.8-188.0] false positives per 1000 women screened vs 95.1 [95% CI, 93.1-97.0] false positives per 1000 women screened). By contrast, triage testing with reflex screening substantially reduced false positives by a factor of approximately 10 (eg, HPV with LBC triage, 9.6 [95% CI, 9.3-10.0] per 1000 women screened). Over a lifetime of screening, reflex approaches with appropriate test intervals maximized therapeutic efficacy; as HPV vaccination rates increased, HPV-based screening approaches resulted in fewer unnecessary colposcopies than LBC approaches (HPV testing, 80% vaccine coverage: 44.1 [95% CI, 40-45.9] excess colposcopies; LBC testing, 80% vaccine coverage: 96.9 [95% CI, 96.8-97.0] excess colposcopies).Conclusions and relevanceIn this decision analytic model, the effectiveness of cervical cancer screening was dependent on the prevalence of cervical dysplasia and/or HPV infection or vaccination in a population as well as the sensitivity and specificity of various modalities. Although screening is lifesaving, overtesting or modalities inappropriate to the target population may cause significant harm, including overtreatment.

Project description:BackgroundTo provide quantitative insight into current U.S. policy choices for cervical cancer prevention, we developed a model of human papillomavirus (HPV) and cervical cancer, explicitly incorporating uncertainty about the natural history of disease.MethodsWe developed a stochastic microsimulation of cervical cancer that distinguishes different HPV types by their incidence, clearance, persistence, and progression. Input parameter sets were sampled randomly from uniform distributions, and simulations undertaken with each set. Through systematic reviews and formal data synthesis, we established multiple epidemiologic targets for model calibration, including age-specific prevalence of HPV by type, age-specific prevalence of cervical intraepithelial neoplasia (CIN), HPV type distribution within CIN and cancer, and age-specific cancer incidence. For each set of sampled input parameters, likelihood-based goodness-of-fit (GOF) scores were computed based on comparisons between model-predicted outcomes and calibration targets. Using 50 randomly resampled, good-fitting parameter sets, we assessed the external consistency and face validity of the model, comparing predicted screening outcomes to independent data. To illustrate the advantage of this approach in reflecting parameter uncertainty, we used the 50 sets to project the distribution of health outcomes in U.S. women under different cervical cancer prevention strategies.ResultsApproximately 200 good-fitting parameter sets were identified from 1,000,000 simulated sets. Modeled screening outcomes were externally consistent with results from multiple independent data sources. Based on 50 good-fitting parameter sets, the expected reductions in lifetime risk of cancer with annual or biennial screening were 76% (range across 50 sets: 69-82%) and 69% (60-77%), respectively. The reduction from vaccination alone was 75%, although it ranged from 60% to 88%, reflecting considerable parameter uncertainty about the natural history of type-specific HPV infection. The uncertainty surrounding the model-predicted reduction in cervical cancer incidence narrowed substantially when vaccination was combined with every-5-year screening, with a mean reduction of 89% and range of 83% to 95%.ConclusionWe demonstrate an approach to parameterization, calibration and performance evaluation for a U.S. cervical cancer microsimulation model intended to provide qualitative and quantitative inputs into decisions that must be taken before long-term data on vaccination outcomes become available. This approach allows for a rigorous and comprehensive description of policy-relevant uncertainty about health outcomes under alternative cancer prevention strategies. The model provides a tool that can accommodate new information, and can be modified as needed, to iteratively assess the expected benefits, costs, and cost-effectiveness of different policies in the U.S.

Project description:ImportanceHuman papillomavirus (HPV) vaccination coverage is suboptimal in the US. The association between HPV vaccination requirements for school entry and HPV vaccination coverage remains to be studied.ObjectiveTo examine the association between HPV vaccination school-entry requirements and vaccination initiation in jurisdictions with such vaccination policies (ie, Virginia, the District of Columbia, and Rhode Island) compared with other regions of the US, as determined by the National Center for Chronic Disease Prevention and Health Promotion.Design, setting, and participantsIn a population-based, cross-sectional study, 2017 data from the National Immunization Survey-Teen database were used to determine HPV vaccination initiation. Data from 2008 to 2017 were then examined to assess the association between HPV vaccination school-entry policies and vaccination initiation. Data were obtained for adolescents aged 13 to 17 years in the US with health care professional-reported HPV vaccination histories (cross-sectional study, n = 4784; pre-post policy comparisons, n = 42 431). This study was conducted from May 1, 2019, to March 31, 2020.ExposuresState-level HPV vaccination school-entry requirements from 2008 to 2017.Main outcomes and measuresHealth care professional-confirmed HPV vaccination initiation.ResultsThe 2017 cross-sectional study included 4784 adolescents aged 13 to 17 years (2228 [46.6%] girls; 2556 [53.4%] boys; mean [SD] age, 15.0 [1.4] years; interquartile range, 14-16 years). Compared with nonpolicy jurisdictions within the same region, Rhode Island and the District of Columbia, which have HPV immunization school-entry requirements, had higher levels of HPV vaccination initiation (Rhode Island: adjusted odds ratio [aOR], 4.34; 95% CI, 2.16-10.00; District of Columbia: aOR, 2.35; 95% CI, 1.39-4.19). However, compared with regional nonpolicy states, Virginia's HPV vaccination initiation did not differ significantly (aOR, 1.01; 95% CI, 0.72-1.42). The 2008-2017 pre-post policy comparisons involved 42 431 adolescents aged 13-17 years (22 362 [52.7%] girls; 20 069 [47.3%] boys; mean [SD] age, 15.0 [1.4] years; interquartile range, 14-16 years). Postpolicy levels of HPV vaccination initiation in girls was significantly higher in Rhode Island (aOR, 3.12; 95% CI, 1.92-5.07) than prepolicy values. Similar changes were noted for postpolicy HPV vaccination initiation in boys in the District of Columbia (aOR, 6.36; 95% CI, 4.27-9.46) and Rhode Island (aOR, 5.84; 95% CI, 3.92-8.69) compared with prepolicy measures. With respect to regional nonpolicy states during the same period, both girls and boys in Rhode Island and boys in the District of Columbia experienced larger increases in HPV vaccination initiation. For example, in Rhode Island, boys aged 16 to 17 years had 7.32 (95% CI, 3.56-15.06) times the change in pre-post policy HPV vaccination initiation, while girls aged 16 to 17 years had 1.28 (95% CI, 0.60-2.73) times the change. In the District of Columbia, boys had 6.36 (95% CI, 4.27-9.46) times the change in pre-post policy HPV vaccination initiation.Conclusions and relevanceThe findings of this study suggest that HPV vaccination school-entry requirements are associated with increases in vaccination initiation. Expanding such policies may increase HPV vaccination in the US.

Dataset Information

Impacts of human papillomavirus vaccination for different populations: A modeling study.

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Impacts of human papillomavirus vaccination for different populations: A modeling study.

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