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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 rates remain significantly below rates for other common childhood vaccines, which has implications for future rates of HPV-associated oropharyngeal squamous cell carcinoma (OPSCC).ObjectiveTo assess whether individuals who were aware of the association between HPV and OPSCC would be more likely to have been previously vaccinated.Design, setting, and participantsThis survey study included patients aged 18 to 45 years who sought routine outpatient care at the otolaryngology clinic at Boston Medical Center from September 1, 2020, to May 19, 2021. A survey (HPV-Associated Head and Neck Cancer Epidemiology, Awareness and Demographics) [HEAD]) composed of validated questions to assess patient knowledge of HPV and HPV vaccination and barriers to vaccination was delivered to participants. The survey was paired with a novel point-of-care vaccination program housed within an otolaryngology department.Main outcomes and measuresThe main outcome was prevalence of knowledge of the relationship between HPV infection and OPSCC based on survey responses. The association of knowledge of HPV-associated OPSCC with likelihood of having been vaccinated was assessed in the overall cohort and by demographic characteristics using multivariate logistic regression.ResultsOf 405 patients given the survey, 288 (71.1%) responded. Of these patients, 271 (94.1%) had surveys included; 158 (58.3%) were female, and median age was 29 years (IQR, 24-35 years). The baseline vaccination rate in the surveyed population was low (26.6%; n = 72) overall (10.6% among men [12 of 113]; 37.9% among women [60 of 158]). Few participants understood the relationship between HPV infection and OPSCC (63 of 271 [23.3%]) or that HPV-associated OPSCC is the most common HPV-associated cancer type (9 of 121 [7.4%]). Compared with men, women were more likely to have been previously vaccinated (odds ratio [OR], 6.5; 95% CI, 3.0-13.9), more aware that HPV causes cancer (OR, 3.7; 95% CI, 1.9-7.1), and more likely to have heard about HPV and HPV vaccination from their health care practitioner (OR, 2.6; 95% CI, 1.2-5.7). Knowledge of the relationship between HPV infection and cancer and between HPV and OPSCC was associated with increased likelihood of having been vaccinated (HPV and cancer: OR, 4.1 [95% CI, 1.8-9.5]; HPV and OPSCC: OR, 3.7 [95% CI, 1.8-7.6]). Among 156 unvaccinated participants, 12 of 98 men (12.2%) and 7 of 131 women (5.3%) received point-of-care vaccination.ConclusionsMost participants in this survey study were unaware that HPV causes OPSCC. Understanding that HPV causes OPSCC was associated with increased likelihood of having been vaccinated. However, most patients surveyed were not informed of this relationship by their health care practitioners. Targeted education aimed at unvaccinated adults establishing the relationship between HPV infection and OPSCC, paired with point-of-care vaccination, may be an innovative strategy for increasing HPV vaccination rates in adults.

Dataset Information

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

Publications

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

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