Estimating the number needed to vaccinate to prevent diseases and death related to human papillomavirus infection

Projected Public Health Impact of a Universal Rotavirus Vaccination Program in France

OBJECTIVE

In June 2022, French health authorities issued a universal recommendation for routine administration and reimbursement of rotavirus vaccines in infants. Given this recent recommendation by French health authorities, we sought to understand the public health impact of a universal rotavirus vaccination strategy compared with no vaccination.

MATERIALS AND METHODS

A deterministic, age-structured, nonlinear dynamic transmission model, accounting for herd immunity, was developed. We considered 3 vaccination coverage scenarios: high (95%), medium (75%) and low (55%). Model parameter values were based on published modeling and epidemiological literature. Model outcomes included rotavirus gastroenteritis (RVGE) cases and healthcare resource utilization due to RVGE (hospitalizations, general practitioner or emergency department visits), as well as the number needed to vaccinate to prevent 1 RVGE case (mild or severe) and 1 RVGE-related hospitalization. Model calibration and analyses were conducted using Mathematica 11.3.

RESULTS

Over 5 years following implementation, RVGE cases for children under 5 years are estimated to be reduced by 84% under a high vaccination coverage scenario, by 72% under a medium vaccination coverage scenario and by 47% under a low vaccination coverage scenario. Across all scenarios, the number needed to vaccinate to avert 1 RVGE case and hospitalization varied between 1.86-2.04 and 24.15-27.44, respectively.

CONCLUSIONS

Rotavirus vaccination with high vaccination coverage in France is expected to substantially reduce the number of RVGE cases and associated healthcare resource utilization.

Bilateral salpingectomy as an option of permanent contraception at time of caesarean section: A survey of practice

BACKGROUND

Opportunistic bilateral salpingectomy during benign gynaecologic surgery is advocated as a risk-reducing strategy due to the inverse association of epithelial ovarian cancers observed in epidemiological studies in a low-risk setting. Currently, no formal guidance exists for permanent surgical contraception at time of caesarean section in Australia.

AIMS

Our aim was to survey Fellows of the Royal Australian and New Zealand College of Obstetricians and Gynaecologists (RANZCOG) regarding bilateral salpingectomy compared to other procedures offered for permanent contraception at the time of caesarean section.

MATERIALS AND METHODS

An online survey was utilised to collect clinician demographics, opinions, barriers, and justifications in regard to options of permanent surgical contraception at time of caesarean section.

RESULTS

Bilateral salpingectomy was identified as the most effective method of permanent contraception at time of caesarean section. However, only 62% of respondents offer the procedure as a method of permanent contraception. The two most common reasons for clinicians to offer bilateral salpingectomy at time of caesarean section were evidence suggesting a link between the fallopian tube and gynaecological cancer (80%) and efficacy as a permanent form of contraception (16%). The primary barrier identified by 51% of respondents was perceived increased risk of surgical complications, followed by reasoning that it would not allow the possibility of future tubal reversal.

CONCLUSION

This study identifies diverse opinions on surgical approach to permanent contraception at time of caesarean section and offered by clinicians of RANZCOG. Further research is required to establish safety profiles and short- and long-term risks of bilateral salpingectomy.

Number needed to vaccinate with a COVID-19 booster to prevent a COVID-19-associated hospitalization during SARS-CoV-2 Omicron BA.1 variant predominance, December 2021-February 2022, VISION Network: a retrospective cohort study

Background

Understanding the usefulness of additional COVID-19 vaccine doses-particularly given varying disease incidence-is needed to support public health policy. We characterize the benefits of COVID-19 booster doses using number needed to vaccinate (NNV) to prevent one COVID-19-associated hospitalization or emergency department encounter.

Methods

We conducted a retrospective cohort study of immunocompetent adults at five health systems in four U.S. states during SARS-CoV-2 Omicron BA.1 predominance (December 2021-February 2022). Included patients completed a primary mRNA COVID-19 vaccine series and were either eligible to or received a booster dose. NNV were estimated using hazard ratios for each outcome (hospitalization and emergency department encounters), with results stratified by three 25-day periods and site.

Findings

1,285,032 patients contributed 938 hospitalizations and 2076 emergency department encounters. 555,729 (43.2%) patients were aged 18-49 years, 363,299 (28.3%) 50-64 years, and 366,004 (28.5%) ≥65 years. Most patients were female (n = 765,728, 59.6%), White (n = 990,224, 77.1%), and non-Hispanic (n = 1,063,964, 82.8%). 37.2% of patients received a booster and 62.8% received only two doses. Median estimated NNV to prevent one hospitalization was 205 (range 44-615) and NNV was lower across study periods for adults aged ≥65 years (110, 46, and 88, respectively) and those with underlying medical conditions (163, 69, and 131, respectively). Median estimated NNV to prevent one emergency department encounter was 156 (range 75-592).

Interpretation

The number of patients needed to receive a booster dose was highly dependent on local disease incidence, outcome severity, and patient risk factors for moderate-to-severe disease.

Funding

Funding was provided by the Centers for Disease Control and Prevention though contract 75D30120C07986 to Westat, Inc. and contract 75D30120C07765 to Kaiser Foundation Hospitals.

Cost-Effectiveness Analysis of Vaccination With Recombinant Zoster Vaccine Among Hematopoietic Cell Transplant Recipients and Persons With Other Immunocompromising Conditions Aged 19 to 49 Years

OBJECTIVES

This study aimed to estimate the cost-effectiveness of the use of recombinant zoster vaccine (RZV) (Shingrix), which protects against herpes zoster (HZ), among immunocompromised adults aged 19 to 49 years, as a contribution to deliberations of the Advisory Committee on Immunization Practices.

METHODS

Hematopoietic cell transplant (HCT) recipients experience a high incidence of HZ, and the efficacy of RZV in preventing HZ has been studied in clinical trials. The cost-effectiveness model calculated incremental cost-effectiveness ratios that compared vaccination with RZV with a no vaccination strategy among adults aged 19 to 49 years. Costs and outcomes were calculated until age 50 years using the healthcare sector perspective and summarized as cost per quality-adjusted life-year (QALY) gained. The base case represents HCT recipients, with scenario analyses representing persons with other immunocompromising conditions, including hematologic malignancies, human immunodeficiency virus, and autoimmune and inflammatory conditions. Uncertainty was investigated using univariate, multivariate, and probabilistic sensitivity analyses.

RESULTS

Base-case results indicated vaccination with RZV would avert approximately 35% of HZ episodes and complications, while saving approximately 11% of net costs. Compared with no vaccination, vaccination of HCT recipients with RZV generated cost-savings (ie, lower costs and improved health) in the base case and in 81% of simulations in the probabilistic analysis. In scenario analyses, vaccination cost US dollar ($) 9500/QALY among patients with hematologic malignancies, $79 000/QALY among persons living with human immunodeficiency virus, and $208 000/QALY among persons with selected autoimmune and inflammatory conditions.

CONCLUSIONS

Generally favorable economic estimates supported recommendations for vaccination of immunocompromised adults with RZV to prevent episodes of HZ and related complications.

Risk of Guillain-Barré syndrome after vaccination against human papillomavirus: a systematic review and meta-analysis, 1 January 2000 to 4 April 2020

BackgroundGuillain-Barré syndrome (GBS) is a rare autoimmune disease that can follow viral infections and has in a few cases been linked to vaccinations. Pre-licensure clinical trials did not observe an association between human papillomavirus (HPV) vaccination and GBS, a post-marketing study from 2017 reported an increased relative risk.AimWe assessed the risk of GBS after HPV vaccination through a systematic literature review and meta-analysis.MethodsWe searched Embase, MEDLINE and Cochrane for studies reporting on the risk of GBS after HPV vaccination in individuals aged ≥ 9 years, published between 1 January 2000 and 4 April 2020, excluding studies without a comparator group. Seven studies reporting relative effect sizes were pooled using random-effects meta-analysis. We assessed quality of evidence using the GRADE approach. Study protocol was registered (PROSPERO No. #CRD42019123533).ResultsOf 602 identified records, we included 25 studies. Based on over 10 million reports, cases of GBS were rare. In 22 studies no increased risk was observed, while in three studies a signal of increased risk of GBS after HPV vaccination was identified. Meta-analysis yielded a pooled random-effects ratio of 1.21 (95% CI: 0.60-2.43); I2 = 72% (95% CI: 36-88). This translates to a number needed to harm of one million to be vaccinated to generate one GBS case. Quality of evidence was very low.ConclusionsThe absolute and relative risk of GBS after HPV vaccination is very low and lacks statistical significance. This is reassuring for the already implemented vaccination programmes and should be used in respective communication activities.

A retrospective cohort study of tubal occlusion or salpingectomy for permanent contraception in Australia

BACKGROUND

Laparoscopic permanent contraception was previously accomplished most commonly using tubal occlusion procedures. Bilateral salpingectomy (BS) has recently been introduced as an alternative due to possibly superior contraception and greater protection against ovarian cancer.

AIMS

The aim of this study is to assess uptake, feasibility and perioperative outcomes of laparoscopic BS as an alternative to tubal occlusion in Australia.

MATERIALS AND METHODS

A retrospective review of permanent female contraception at two Australian hospitals from January 2014 through December 2020 was performed. The primary outcome was the uptake of BS. Secondary outcomes were feasibility, procedure length, number of ports, perioperative complications and admission length.

RESULTS

A total of 414 women were included; 92 (22.2%) underwent BS and 322 (77.8%) underwent tubal occlusion. There was a slow uptake of BS from 2014 to 2016 (0-3.2%), with a steep uptake from 2017 to 2020 (30-72%) (P = 0.001). Procedure feasibility was 96.8% (62/64) and 99.3% (282/284) for BS and tubal occlusion group, respectively (P = 0.64). BS procedure time was longer by 23 min (P < 0.001). Three or more surgical ports were used in all cases of BS compared to 4.5% of the tubal occlusion group (P < 0.001). There were no intraoperative complications. There were nine and six postoperative complications in the tubal occlusion versus BS group, respectively (P = 0.10). The median admission length was 7.1 (tubal occlusion) versus 7.3 (BS) h (P = 0.10), with five unintended overnight admissions.

CONCLUSION

BS is an increasing choice for permanent contraception. It appears equally feasible as tubal occlusion but typically requires a longer procedure time and a minimum of three surgical ports.

Estimated Impact of World Health Organization Latent Tuberculosis Screening Guidelines in a Region With a Low Tuberculosis Incidence: Retrospective Cohort Study

BACKGROUND

Latent tuberculosis infection (LTBI) screening and treatment is a key component of the World Health Organization (WHO) EndTB Strategy, but the impact of LTBI screening and treatment at a population level is unclear. We aimed to estimate the impact of LTBI screening and treatment in a population of migrants to British Columbia (BC), Canada.

METHODS

This retrospective cohort included all individuals (N = 1 080 908) who immigrated to Canada as permanent residents between 1985 and 2012 and were residents in BC at any time up to 2013. Multiple administrative databases were linked to identify people with risk factors who met the WHO strong recommendations for screening: people with tuberculosis (TB) contact, with human immunodeficiency virus, on dialysis, with tumor necrosis factor-alpha inhibitors, who had an organ/haematological transplant, or with silicosis. Additional TB risk factors included immunosuppressive medications, cancer, diabetes, and migration from a country with a high TB burden. We defined active TB as preventable if diagnosed ≥6 months after a risk factor diagnosis. We estimated the number of preventable TB cases, given optimal LTBI screening and treatment, based on these risk factors.

RESULTS

There were 16 085 people (1.5%) identified with WHO strong risk factors. Of the 2814 people with active TB, 118 (4.2%) were considered preventable through screening with WHO risk factors. Less than half (49.4%) were considered preventable with expanded screening to include people migrating from countries with high TB burdens, people who had been prescribed immunosuppressive medications, or people with diabetes or cancer.

CONCLUSIONS

The application of WHO LTBI strong recommendations for screening would have minimally impacted the TB incidence in this population. Further high-risk groups must be identified to develop an effective LTBI screening and treatment strategy for low-incidence regions.

Potential lives saved in 73 countries by adopting multi-cohort vaccination of 9-14-year-old girls against human papillomavirus

Up to 2016, low- and middle-income countries mostly introduced routine human papillomavirus (HPV) vaccination for just a single age-cohort of girls each year. However, high-income countries have reported large reductions in HPV prevalence following "catch-up" vaccination of multiple age-cohorts in the year of HPV vaccine introduction. We used the mathematical model PRIME to project the incremental impact of vaccinating 10- to 14-year-old girls compared to routine HPV vaccination only in the same year that routine vaccination is expected to be introduced for 9-year-old girls across 73 low- and lower-middle-income countries. Adding multiple age-cohort vaccination could increase the number of cervical cancer deaths averted by vaccine introductions in 2015-2030 by 30-40% or an additional 1.23-1.79 million over the lifetime of the vaccinated cohorts. The number of girls needed to vaccinate to prevent one death is 101 in the most pessimistic scenario, which is only slightly greater than that for routine vaccination of 9-year-old girls (87). These results hold even when assuming that girls who have sexually debuted do not benefit from vaccination. Results suggest that multiple age-cohort vaccination of 9- to 14-year-old girls could accelerate HPV vaccine impact and be cost-effective.

Rethinking number-needed-to-vaccinate for pneumococcal conjugate vaccines in older adults: Current and future implications

BACKGROUND

Number-needed-to-vaccinate (NNV) is increasingly used to inform decisions about vaccine use, but it is not calculated uniformly across studies. This study compared two methodologies for calculating NNV with 13-valent pneumococcal conjugate vaccine (PCV13) to prevent one case of community-acquired pneumonia (CAP) among US adults aged ≥65years: (i) using one-year absolute rate differences as was originally performed by the Centers for Disease Control and Prevention (CDC) and (ii) using absolute risk reduction over 5years.

METHODS

We constructed a hypothetical fixed cohort of 200,000 adults aged ≥65years equally separated into PCV13-vaccinated and PCV13-unvaccinated groups. We incorporated the same conservative assumptions used by CDC in 2014 regarding annual incidence of hospitalized (1375 per 100,000) and outpatient (2010 per 100,000) CAP, the initial (2014) proportion of adult PCV13-type CAP (10%), and PCV13 efficacy against vaccine-type CAP (45%). To model PCV13 impact over time, we assumed annual mortality was 5% for both groups, the percentage of adult PCV13-type CAP declined annually due to pediatric herd effects, and PCV13 efficacy did not wane over 5years.

RESULTS

Among adults aged ≥65years, NNV with PCV13 to prevent one hospitalized and one outpatient case of CAP as originally calculated by CDC in 2014 were 1620 and 1110, respectively. Accounting for 5-year cumulative effects, NNV with PCV13 to prevent one hospitalized and one outpatient case of CAP over 5years were 576 and 394, respectively. These revised NNV estimates are roughly one third of initial estimates in which cumulative effects were ignored. NNV to prevent any CAP (inpatient or outpatient) over 5years with one PCV13 dose was 234.

CONCLUSION

Accounting for cumulative preventive effects of PCV13 vaccination over time is critical. Failing to do so, even when using conservative disease burden parameters, can grossly underestimate the public health impact of adult PCV13 use.

Role of salpingectomy at the time of urogynecologic surgery

PURPOSE OF REVIEW

This article reviews the current literature about prophylactic bilateral salpingectomy and provides guidelines for clinicians in regard to the inclusion of salpingectomy at the time of urogynecologic surgery.

RECENT FINDINGS

After the Nurses' Health Study showed that all-cause mortality was increased in women undergoing oophorectomy at the time of hysterectomy for benign indications, there was a shift in focus toward ovarian conservation at the time of gynecologic surgery. As there has been continued interest in the fallopian tube as the origin of ovarian cancer, a move toward prophylactic salpingectomy has occurred. This strategy has become widely accepted in high-risk women, but is not universal in either premenopausal or postmenopausal women who are primarily served by the urogynecologic community.

SUMMARY

Current literature supports that, if easily accessible, the fallopian tubes should be removed at the time of urogynecologic surgery. In premenopausal women, salpingectomy does not likely affect ovarian reserve, but this possibility should be discussed with patients. If inaccessible (i.e., at the time of a midurethral sling), there should not be additional surgery performed to access the fallopian tubes. In addition, the pathologic evaluation of the fallopian tubes should include complete examination of the fimbriae and a representative section of the nonfimbriated portion.

Opportunistic salpingectomy for ovarian cancer prevention

Recently accumulated evidence has strongly indicated that the fallopian tube is the site of origin for the majority of high-grade serous ovarian or peritoneal carcinomas. As a result, recommendations have been made to change surgical practice in women at general population risk for ovarian cancer and perform bilateral salpingectomy at the time of hysterectomy without oophorectomy and in lieu of tubal ligation, a practice that has been termed opportunistic salpingectomy (OS). Despite suggestions that bilateral salpingectomy may be used as an interim procedure in women with BRCA1/2 mutations, enabling them to delay oophorectomy, there is insufficient evidence to support this practice as a safe alternative and risk-reducing bilateral salpingo-oophorectomy remains the recommended standard of care for high-risk women. While evidence on uptake of OS is sparse, it points toward increasing practice of OS during hysterectomy. The practice of OS for sterilization purposes, although expanding, appears to be less common. Operative and perioperative complications as measured by administered blood transfusions, hospital length of stay and readmissions were not increased with the addition of OS either at time of hysterectomy or for sterilization. Additional operating room time was 16 and 10 min for OS with hysterectomy and OS for sterilization, respectively. Short-term studies of the consequences of OS on ovarian function indicate no difference between women undergoing hysterectomy alone and hysterectomy with OS, but no long-term data exist. There is emerging evidence of effectiveness of excisional sterilization on reducing ovarian cancer rates from Rochester (OR = 0.36 95 % CI 0.13, 1.02), and bilateral salpingectomy from Denmark (OR = 0.58 95 % CI 0.36, 0.95) and Sweden (HR = 0.35, 95 % CI 0.17, 0.73), but these studies suffer from limitations, including that they were performed for pathological rather than prophylactic purposes. Initial cost-effectiveness modeling indicates that OS is cost-effective over a wide range of costs and risk estimates. While preliminary safety, efficacy, and cost-effectiveness data are promising, further research is needed (particularly long-term data on ovarian function) to firmly establish the safety of the procedure. The marginal benefit of OS compared with tubal ligation or hysterectomy alone needs to be established through large prospective studies of OS done for prophylaxis.

Costs and benefits of opportunistic salpingectomy as an ovarian cancer prevention strategy

OBJECTIVE

To conduct a cost-effectiveness analysis of opportunistic salpingectomy (elective salpingectomy at hysterectomy or instead of tubal ligation).

METHODS

A Markov Monte Carlo simulation model estimated the costs and benefits of opportunistic salpingectomy in a hypothetical cohort of women undergoing hysterectomy for benign gynecologic conditions or surgical sterilization. The primary outcome measure was the incremental cost-effectiveness ratio. Effectiveness was measured in terms of life expectancy gain. Sensitivity analyses accounted for uncertainty around various parameters. Monte Carlo simulation estimated the number of ovarian cancer cases associated with each strategy in the Canadian population.

RESULTS

Salpingectomy with hysterectomy was less costly ($11,044.32 ± $1.56) than hysterectomy alone ($11,206.52 ± $29.81) or with bilateral salpingo-oophorectomy ($12,626.84 ± $13.11) but more effective at 21.12 ± 0.02 years compared with 21.10 ± 0.03 and 20.94 ± 0.03 years, representing average gains of 1 week and 2 months, respectively. For surgical sterilization, salpingectomy was more costly ($9,719.52 ± $3.74) than tubal ligation ($9,339.48 ± $26.74) but more effective at 22.45 ± 0.02 years compared with 22.43 ± 0.02 years (average gain of 1 week) with an incremental cost-effectiveness ratio of $27,278 per year of life gained. Our results were stable over a wide range of costs and risk estimates. Monte Carlo simulation predicted that salpingectomy would reduce ovarian cancer risk by 38.1% (95% confidence interval [CI] 36.5-41.3%) and 29.2% (95% CI 28.0-31.4%) compared with hysterectomy alone or tubal ligation, respectively.

CONCLUSION

Salpingectomy with hysterectomy for benign conditions will reduce ovarian cancer risk at acceptable cost and is a cost-effective alternative to tubal ligation for sterilization. Opportunistic salpingectomy should be considered for all women undergoing these surgical procedures.

Examining Provincial HPV Vaccination Schemes in Canada: Should We Standardise the Grade of Vaccination or the Number of Doses?

Human papillomavirus (HPV) infection is the most common sexually transmitted infection, which is linked to several cancers and genital warts. Depending on the Canadian province, the quadrivalent vaccine is given to girls in grades 4 through 10 with either a two- or three-dose schedule. We use a mathematical model to address the following research questions: (1) Does the grade at which the girls are vaccinated significantly affect the outcome of the program? (2) What coverage rate must the provinces reach in order to reduce the impact of HPV on the Canadian population? (3) What are the implications of vaccinating with two versus three doses? The model suggests the grade of vaccination and the number of doses do not make a significant difference to the outcome of the public vaccination program. The most significant factor is the coverage rate of children and adults. We recommend that provinces vaccinate as early as possible to avoid vaccine failure due to previous infection. We also recommend that the main focus of the program should be on obtaining a large enough coverage rate for children and/or adults in order to achieve the desired outcome with either two or three doses of the vaccine.

How and why researchers use the number needed to vaccinate to inform decision making--a systematic review

BACKGROUND

The number needed to vaccinate (NNV) is a measure that has been widely used in the scientific literature to draw conclusions about the usefulness and cost-effectiveness of various immunization programmes. The main objective of this review is to examine how and why the NNV has been used and reported in the published literature.

METHODS

Electronic databases were searched and records were screened against the eligibility criteria by two independent authors. We included papers that reported and interpreted NNV.

RESULTS

We identified 27 studies, the designs including observational studies, economic analyses, systematic reviews, and commentaries. The NNV has been used in the literature to describe three main themes: potential benefits of vaccination programmes, cost-effectiveness, and economic analyses, and modelling studies to compare different vaccination strategies.

CONCLUSIONS

NNV has been used in a wide variety of ways in the literature, yet there are no defined thresholds for what is a favourable NNV. Furthermore, the generalizability of the NNV is usually limited. Further work is required to determine the most appropriate use of this measure.

A cocoon immunisation strategy against pertussis for infants: does it make sense for Ontario?

Pertussis deaths occur primarily among infants who have not been fully immunised. In Ontario, Canada, an adult booster dose was recently added to the publicly funded immunisation programme. We applied number-needed-to-treat analyses to estimate the number of adults that would need to be vaccinated (NNV) to prevent pertussis disease, hospitalisation and death among infants if a cocoon strategy were implemented. NNV=1/(P(M) X R) + 1/(P(F) X R), where P(M),P(F) (proportion of infants infected by mothers, fathers) were sourced from several studies. Rates of disease, hospitalisation or death (R) were derived from Ontario's reportable disease data and Discharge Abstract Database. After adjusting for under-reporting, the NNV to prevent one case, hospitalisation or death from pertussis was between 500-6,400, 12,000-63,000 and 1.1-12.8 million, respectively. Without adjustment, NNV increased to 5,000-60,000, 55,000-297,000 and 2.5-30.2 million, respectively. Rarer outcomes were associated with higher NNV. These analyses demonstrate the relative inefficiency of a cocoon strategy in Ontario, which has a well-established universal immunisation programme with relatively high coverage and low disease incidence. Other jurisdictions considering a cocoon programme should consider their local epidemiology.

Human papilloma virus vaccination programs reduce health inequity in most scenarios: a simulation study

BACKGROUND

The global and within-country epidemiology of cervical cancer exemplifies health inequity. Public health programs may reduce absolute risk but increase inequity; inequity may be further compounded by screening programs. In this context, we aimed to explore what the impact of human papillomavirus (HPV) vaccine might have on health equity allowing for uncertainty surrounding the long-term effect of HPV vaccination programs.

METHODS

A simple static multi-way sensitivity analysis was carried out to compare the relative risk, comparing after to before implementation of a vaccination program, of infections which would cause invasive cervical cancer if neither prevented nor detected, using plausible ranges of vaccine effectiveness, vaccination coverage, screening sensitivity, screening uptake and changes in uptake.

RESULTS

We considered a total number of 3,793,902 scenarios. In 63.9% of scenarios considered, vaccination would lead to a better outcome for a population or subgroup with that combination of parameters. Regardless of vaccine effectiveness and coverage, most simulations led to lower rates of disease.

CONCLUSIONS

If vaccination coverage and screening uptake are high, then communities are always better off with a vaccination program. The findings highlight the importance of achieving and maintaining high immunization coverage and screening uptake in high risk groups in the interest of health equity.

Time for change? An economic evaluation of integrated cervical screening and HPV immunization programs in Canada

Many jurisdictions have implemented universal human papillomavirus (HPV) immunization programs in preadolescent females. However, the cost-effectiveness of modified cervical screening guidelines and/or catch-up immunization in older females in Canada has not been evaluated. We conducted a cost-utility analysis of screening and immunization with the bivalent vaccine for the Canadian setting from the Ministry of Health perspective. We used a dynamic model to capture herd immunity and included cross-protection against strains not included in the vaccine. We found that adding catch-up immunization to the current program would be cost-effective, and that combining catch-up immunization with delaying the age at which screening is first initiated could result in cost savings and net health gains.

Childhood immunization: when physicians and parents disagree

Persistent fears about the safety and efficacy of vaccines, and whether immunization programs are still needed, have led a significant minority of parents to refuse vaccination. Are parents within their rights when refusing to consent to vaccination? How ought physicians respond? Focusing on routine childhood immunization, we consider the ethical, legal, and clinical issues raised by 3 aspects of parental vaccine refusal: (1) physician counseling; (2) parental decision-making; and (3) continuing the physician-patient relationship despite disagreement. We also suggest initiatives that could increase confidence in immunization programs.

The paradox of HPV vaccines: how to reach sexually inexperienced women for protection against a sexually transmitted infection

PURPOSE

The current study examined the impact of a human papillomavirus (HPV) vaccine message tailored for sexually inexperienced women.

METHODS

We included 193 young women, aged 17 to 26, attending university, who completed an on-line questionnaire. The participants were randomly assigned to three conditions that manipulated the type of information they received on HPV and the vaccine: control (minimal information, sexual transmission information omitted), detailed (emphasized sexual transmission of HPV), or tailored (the same as detailed, but also emphasized the benefit to sexually inexperienced women).

RESULTS

Women with no sexual experience intended to receive an HPV vaccine more in the tailored condition than the detailed condition (q = 3.46; p < .05) and the control condition (q = 5.11; p < .01). There was no difference between the detailed condition compared with the control condition (q = 1.45; p = NS).

CONCLUSION

This study found that a message tailored for sexually inexperienced women resulted in higher intentions to receive the HPV vaccine compared with messages that were not tailored. When providing information about HPV vaccines to sexually inexperienced patients, it may be particularly important to emphasize that HPV vaccines are most efficacious if received before the onset of sexual activity. The results suggest that this is more effective in increasing sexually inexperienced women's interest in the vaccine than avoiding information about sexual transmission altogether.

Longer term efficacy of a prophylactic monovalent human papillomavirus type 16 vaccine

We conducted an extended follow-up study (March 2006-May 2008) to assess the longer term efficacy of a prophylactic monovalent human papillomavirus (HPV) type 16 L1 virus-like particle vaccine in women (n=290) who had enrolled in a randomized controlled trial of this vaccine (October 1998-November 1999) in Seattle and remained HPV-16 DNA negative during the course of that trial. During the extended follow-up period, in the per-protocol susceptible population, none of the vaccine recipients was found to be infected with HPV-16 or developed HPV-16-related cervical lesions; among placebo recipients, 6 women were found to be infected with HPV-16 (vaccine efficacy [VE]=100%; 95% confidence interval [CI]: 29-100%) and 3 women developed HPV-16-related cervical lesions (VE=100%; 95% CI: <0-100%). Approximately 86% of vaccine recipients remained HPV-16 competitive Luminex immunoassay seropositive at an average of 8.5 years of follow-up. During the combined original trial and extended follow-up period, in the intention-to-treat population, 20 and 22 women developed any cervical lesion regardless of HPV type among the vaccine and placebo recipients, respectively (VE=15%; 95% CI: <0-56%). The results suggest that this monovalent HPV-16 vaccine remains efficacious through 8.5 years after its administration.

Defining a strategy to evaluate cervical cancer prevention and early detection in the era of HPV vaccination

OBJECTIVE

The purpose of this paper is to outline the short-, medium- and long-term requirements of a strategy to evaluate the impact of HPV immunization and to define a framework to facilitate planning and evaluation.

METHOD

This strategy was developed in Ontario from January to August 2008. Literature review was completed to assess existing material relevant to vaccine evaluation, and HPV vaccine specifically. Scientists and epidemiologists within our organization attended meetings to brainstorm and identify key requirements for vaccine evaluation. Other selected internal and external experts were consulted to review preliminary lists of potential indicators and questions for inclusion in an evaluation strategy.

RESULTS

Results are reported in three sections--literature review, proposed evaluation framework and data requirements.

CONCLUSION

The first vaccine evaluation strategy that integrates primary and secondary prevention of cervical cancer is presented. Among women who are neither screened nor immunized, customized interventions will be required to ensure that they are aware of potential risks and benefits. This evaluation strategy may serve as a useful outline for jurisdictions in Canada and elsewhere. This new paradigm of combined primary and secondary intervention will encourage cooperation for effective evaluation of an integrated approach for control of cervical cancer and other HPV-related disease.

Estimating the number needed to vaccinate to prevent herpes zoster-related disease, health care resource use and mortality

BACKGROUND

A clinical trial has shown that a live-attenuated varicella-zoster virus vaccine is effective against herpes zoster (HZ) and post-herpetic neuralgia (PHN). The aim of the study was to estimate the number needed to vaccinate (NNV) to prevent HZ-related outcomes.

METHODS

A cohort model of HZ associated disease, health care resource use and mortality was developed. Canadian population-based data were used to estimate age-specific incidence, hospitalization, quality-adjusted life-year (QALY) lost and mortality. NNV was calculated as the number of individuals needed to be vaccinated to prevent a specific HZ-related outcome during their lifetime. Different ages at vaccination were examined and probabilistic sensitivity analysis was performed.

RESULTS

For 65 year olds, the NNV (HZ vaccine efficacy=63%, PHN vaccine efficacy=67%, no waning) to prevent a case of HZ, a case of PHN, a HZ death, a life-year lost and a QALY lost is estimated to be 11 (90% Crl: 10-13), 43 (90% Crl: 33-53), 23,319 (90% Crl: 15,312-33,139), 3762 (90% Crl: 1650-4629) and 165 (90% Crl: 105-197), respectively. Results were most sensitive to the duration of vaccine protection and the age at vaccination.

DISCUSSION

The predicted NNV to prevent HZ and PHN are low even though vaccine efficacy is between 50-70%, which reflects the high incidence of these diseases among older adults. Results clearly show that the main benefit of HZ vaccination is prevention of morbidity caused by pain (as measured by QALYs lost) rather than mortality.

Cost-effectiveness evaluation of a quadrivalent human papillomavirus vaccine in Belgium

BACKGROUND

The introduction of a quadrivalent human papillomavirus (HPV; types 6, 11, 16, 18) vaccine is expected to significantly reduce the burden of cervical cancer, cervical intraepithelial neoplasia (CIN), genital warts and other HPV-related diseases.

OBJECTIVE

To determine the cost effectiveness of providing a quadrivalent (6,11,16,18) HPV vaccine programme in adolescent females aged 12 years in addition to the existing cervical cancer screening programme in Belgium.

METHODS

A Markov state-transition model was developed for the Belgian context in order to evaluate the long-term impact of vaccinating a cohort of girls aged 12 years alongside the existing screening programme. Women were followed until the age of 85 years. A vaccine that would prevent 100% of diseases associated with HPV-6, -11, -16 and -18, with lifetime duration of efficacy, 80% coverage, in conjunction with current screening, was compared with screening alone. For this analysis, 35% of cases of CIN-1, 55% of CIN-2/3, 75% of cervical cancer and 90% of genital warts were considered to be attributable to HPV-6, -11, -16 or -18. The model estimated lifetime risks and total lifetime healthcare costs, survival and QALYs for cervical cancer, CIN and genital warts. Outcomes validation was applied. Model outcomes also included incremental costs per life-year gained and incremental costs per QALY gained. The analysis was conducted from the perspective of the Belgian healthcare payer, and costs were in year 2006 values.

RESULTS

The model estimated a reduction in the lifetime risk of cervical cancer from 0.94% to 0.34%, therefore preventing 362 cases of cervical cancer and 131 related deaths in a cohort of 60,000 girls aged 12 years in Belgium. The base-case scenario suggests quadrivalent HPV vaccination in addition to current cervical screening in Belgium to be cost effective at euro 10,546 per QALY. This is within the accepted range of cost-effective interventions in Europe. This cost effectiveness is maintained for different parameter assumptions in the sensitivity analysis, with the exception of very high discount rates for costs and medical benefits, but, even in the worst case, ratios were still less than euro 50,000 per QALY. Even when a separate scenario modelled the requirement for a booster vaccination to sustain a lifetime duration of protection, the results remained cost effective at eruo 17,388 per QALY.

CONCLUSIONS

Vaccination with a quadrivalent HPV vaccine appears to be a cost-effective public health intervention in conjunction with the existing screening programme in Belgium. The additional costs of introducing vaccination to the established screening programme would be offset by the potential savings from not having to treat the diseases caused by HPV-6, -11, -16 or -18.

Modeling cervical cancer prevention in developed countries

Cytology-based screening has reduced cervical cancer mortality in countries able to implement, sustain and financially support organized programs that achieve broad coverage. These ongoing secondary prevention efforts considerably complicate the question of whether vaccination against human papillomavirus (HPV) types 16 and 18 should be introduced. Policy questions focus primarily on the target ages of vaccination, appropriate ages for a temporary "catch-up" program, possible revisions in screening policies to optimize synergies with vaccination, including the increased used of HPV DNA testing, and the inclusion of boys in the vaccination program. Decision-analytic models are increasingly being developed to simulate disease burden and interventions in different settings in order to evaluate the benefits and cost-effectiveness of primary and secondary interventions for informed decision-making. This article is a focused review on existing mathematical models that have been used to evaluate HPV vaccination in the context of developed countries with existing screening programs. Despite variations in model assumptions and uncertainty in existing data, pre-adolescent vaccination of girls has been consistently found to be attractive in the context of current screening practices, provided there is complete and lifelong vaccine protection and widespread vaccination coverage. Questions related to catch-up vaccination programs, potential benefits of other non-cervical cancer outcomes and inclusion of boys are subject to far more uncertainty, and results from these analyses have reached conflicting conclusions. Most analyses find that some catch-up vaccination is warranted but becomes increasingly unattractive as the catch-up age is extended, and vaccination of boys is unlikely to be cost-effective if reasonable levels of coverage are achieved in girls or coverage among girls can be improved. The objective of this review is to highlight points of consensus and qualitative themes, to discuss the areas of divergent findings, and to provide insight into critical decisions related to cervical cancer prevention.