Impact of transmission dynamics on the cost-effectiveness of rotavirus vaccination

On spillovers in economic evaluations: definition, mapping review and research agenda

An important issue in economic evaluations is determining whether all relevant impacts are considered, given the perspective chosen for the analysis. Acknowledging that patients are not isolated individuals has important implications in this context. Increasingly, the term "spillovers" is used to label consequences of health interventions on others. However, a clear definition of spillovers is lacking, and as a result, the scope of the concept remains unclear. In this study, we aim to clarify the concept of spillovers by proposing a definition applicable in health economic evaluations. To illustrate the implications of this definition, we highlight the diversity of potential spillovers through an expanded impact inventory and conduct a mapping review that outlines the evidence base for the different types of spillovers. In the context of economic evaluations of health interventions, we define spillovers as all impacts from an intervention on all parties or entities other than the users of the intervention under evaluation. This definition encompasses a broader range of potential costs and effects, beyond informal caregivers and family members. The expanded impact inventory enables a systematic approach to identifying broader impacts of health interventions. The mapping review shows that the relevance of different types of spillovers is context-specific. Some spillovers are regularly included in economic evaluations, although not always recognised as such, while others are not. A consistent use of the term "spillovers", improved measurement of these costs and effects, and increased transparency in reporting them are still necessary. To that end, we propose a research agenda.

A Systematic Review of Methods Used by Pediatric Cost-Utility Analyses to Include Family Spillover Effects

BACKGROUND

A child's health condition affects family members' health and well-being. However, pediatric cost-utility analysis (CUA) commonly ignores these family spillover effects leading to an incomplete understanding of the cost and benefits of a child's health intervention. Methodological challenges exist in assessing, valuing, and incorporating family spillover effects.

OBJECTIVE

This study systematically reviews and compare methods used to include family spillover effects in pediatric CUAs.

METHODS

A literature search was conducted in MEDLINE, Embase, EconLit, Cochrane collection, CINAHL, INAHTA, and the Pediatric Economic Database Evaluation (PEDE) database from inception to 2020 to identify pediatric CUAs that included family spillover effects. The search was updated to 2021 using PEDE. The data describing in which family members spillover effects were measured, and how family spillover effects were measured, incorporated, and reported, were extracted. Common approaches were grouped conceptually. Further, this review identified theories or theoretical frameworks used to justify approaches for integrating family spillover effects into CUA.

RESULTS

Of 878 pediatric CUAs identified, 35 included family spillover effects. Most pediatric CUAs considered family spillover effects on one family member. Pediatric CUAs reported eight different approaches to measure the family spillover effects. The most common method was measuring the quality-adjusted life years (QALY) loss of the caregiver(s) or parent(s) due to a child's illness or disability using an isolated approach whereby family spillover effects were quantified in individual family members separately from other health effects. Studies used four approaches to integrate family spillover effects into CUA. The most common method was to sum children's and parents/caregivers' QALYs. Only two studies used a theoretical framework for incorporation of family spillover effects.

CONCLUSIONS

Few pediatric CUAs included family spillover effects and the observed variation indicated no consensus among researchers on how family spillover effects should be measured and incorporated. This heterogeneity is mirrored by a lack of practical guidelines by Health Technology Assessment (HTA) agencies or a theoretical foundation for including family spillover effects in pediatric CUA. The results from this review may encourage researchers to develop a theoretical framework and HTA agencies to develop guidelines for including family spillover effects. Such guidance may lead to more rigorous and standardized methods for including family spillover effects and better-quality evidence to inform decision-makers on the cost-effectiveness of pediatric health interventions.

Systematic review of rotavirus vaccination cost-effectiveness in high income settings utilising dynamic transmission modelling techniques

PURPOSE

This systematic review presents cost-effectiveness studies of rotavirus vaccination in high-income settings based on dynamic transmission modelling to inform policy decisions about implementing rotavirus vaccination programmes.

METHODS

We searched CEA Registry, MEDLINE, Embase, Health Technology Assessment Database, Scopus, and the National Health Service Economic Evaluation Database for studies published since 2002. Full economic evaluation studies based on dynamic transmission models, focusing on high-income countries, live oral rotavirus vaccine and children ≤ 5 years of age were eligible for inclusion. Included studies were appraised for quality and risk of bias using the Consensus on Health Economic Criteria (CHEC) list and the Philips checklist. The review protocol was prospectively registered with PROSPERO (CRD42020208406).

RESULTS

A total of four economic evaluations were identified. Study settings included England and Wales, France, Norway, and the United States. All studies compared either pentavalent or monovalent rotavirus vaccines to no intervention. All studies were cost-utility analyses that reported incremental cost per quality-adjusted life year (QALY) gained. Included studies consistently concluded that rotavirus vaccination is cost-effective compared with no vaccination relative to the respective country's willingness to pay threshold when herd protection benefits are incorporated in the modelling framework.

CONCLUSIONS

Rotavirus vaccination was found to be cost-effective in all identified studies that used dynamic transmission models in high-income settings where child mortality rates due to rotavirus gastroenteritis are close to zero. Previous systematic reviews of economic evaluations considered mostly static models and had less conclusive findings than the current study. This review suggests that modelling choices influence cost-effectiveness results for rotavirus vaccination. Specifically, the review suggests that dynamic transmission models are more likely to account for the full impact of rotavirus vaccination than static models in cost-effectiveness analyses.

Imperfect vaccine can yield multiple Nash equilibria in vaccination games

As infectious diseases continue to threaten communities across the globe, people are faced with a choice to vaccinate, or not. Many factors influence this decision, such as the cost of the disease, the chance of contracting the disease, the population vaccination coverage, and the efficacy of the vaccine. While the vaccination games in which individuals decide whether to vaccinate or not based on their own interests are gaining in popularity in recent years, the vaccine imperfection has been an overlooked aspect so far. In this paper we investigate the effects of an imperfect vaccine on the outcomes of a vaccination game. We use a simple SIR compartmental model for the underlying model of disease transmission. We model the vaccine imperfection by adding vaccination at birth and maintain a possibility for the vaccinated individual to become infected. We derive explicit conditions for the existence of different Nash equilibria, the solutions of the vaccination game. The outcomes of the game depend on the complex interplay between disease transmission dynamics (the basic reproduction number), the relative cost of the infection, and the vaccine efficacy. We show that for diseases with relatively low basic reproduction numbers (smaller than about 2.62), there is a little difference between outcomes for perfect or imperfect vaccines and thus the simpler models assuming perfect vaccines are good enough. However, when the basic reproduction number is above 2.62, then, unlike in the case of a perfect vaccine, there can be multiple equilibria. Moreover, unless there is a mandatory vaccination policy in place that would push the vaccination coverage above the value of unstable Nash equilibrium, the population could eventually slip to the "do not vaccinate" state. Thus, for diseases that have relatively high basic reproduction numbers, the potential for the vaccine not being perfect should be explicitly considered in the models.

Systematic Review of Cost-Utility Analyses That Have Included Carer and Family Member Health-Related Quality of Life

OBJECTIVES

Health interventions for patients can also affect the health of their informal carers and family members. These changes in carer or family member health could be reflected in cost-utility analyses (CUAs) through the inclusion of their quality-adjusted life-years (QALYs). We conducted a systematic review to identify and describe all CUAs that have included family member health-related QALYs.

METHODS

A total of 4 bibliographic databases were searched from inception to July 2021. A 2-stage sifting process for inclusion of studies was undertaken. We performed data extraction using a standardized data extraction form and performed a narrative synthesis of the evidence.

RESULTS

A total of 40 CUAs published between 1999 and 2021 were identified. CUAs were conducted in 15 different countries. CUAs examined 13 different conditions including 15 CUAs on vaccination, 5 on Alzheimer's disease, 2 on Parkinson's disease, 3 on dementia, and 2 on terminal illness. The EQ-5D was the most commonly used measure of family member health. Generally, including carer QALYs resulted in lower incremental cost-effectiveness ratios.

CONCLUSIONS

When considering the total number of economic evaluations published, few have included family member QALYs and the methods for doing so are often inconsistent and data sources often limited. Estimation of family member QALYs in patient CUAs was regularly uncertain and often substantial in magnitude. The findings highlight the variation among methods and call for greater consistency in methods for incorporating family member QALYs in patient CUAs.

Overcoming roadblocks in the development of vaccines for leishmaniasis

INTRODUCTION

The leishmaniases represent a group of parasitic diseases caused by infection with one of several species of Leishmania parasites. Disease presentation varies because of differences in parasite and host genetics and may be influenced by additional factors such as host nutritional status or co-infection. Studies in experimental models of Leishmania infection, vaccination of companion animals and human epidemiological data suggest that many forms of leishmaniasis could be prevented by vaccination, but no vaccines are currently available for human use.

AREAS COVERED

We describe some of the existing roadblocks to the development and implementation of an effective leishmaniasis vaccine, based on a review of recent literature found on PubMed, BioRxiv and MedRxiv. In addition to discussing scientific unknowns that hinder vaccine candidate identification and selection, we explore gaps in knowledge regarding the commercial and public health value propositions underpinning vaccine development and provide a route map for future research and advocacy.

EXPERT OPINION

Despite significant progress, leishmaniasis vaccine development remains hindered by significant gaps in understanding that span the vaccine development pipeline. Increased coordination and adoption of a more holistic view to vaccine development will be required to ensure more rapid progress in the years ahead.

The impact of childhood RSV infection on children's and parents' quality of life: a prospective multicenter study in Spain

Background

 Several immunisation candidates against RSV are in late-stage clinical trials. To evaluate the benefits of a potential vaccination programme, both economic and health benefits will be needed. Health benefits are usually measured in Health-related Quality of Life (HRQoL) loss using standardised questionnaires. However, there are no RSV-specific questionnaires validated for children under 2 years, in whom most RSV episodes occur. Therefore, HRQoL estimates are taken from literature or inadequate tools. We determined HRQoL loss and direct costs due to an RSV episode in children younger than 2 years and their caregivers during a month of follow up, using a new questionnaire administered online.

Methods

 An observational prospective multicentre surveillance study was conducted in children aged younger than two years. Children were recruited from 8 primary care centres and 1 hospital in the Valencia region and Catalonia (Spain). RSV-positive cases were obtained by immunochromatographic test. HRQoL was assessed using a new ad-hoc 38 item-questionnaire developed. Parents of infected children completed 4 questionnaires at four timepoints (day 0, 7, 14 and 30) after diagnosis.

Results

 117 children were enrolled in the study and 86 (73.5%) were RSV + . Median (interquartile range; IQR) scores were 0.52 (0.42–0.68), 0.65 (0.49–0.79), 0.82 (0.68–0.97) and 0.94 (0.81–1), for days 0, 7, 14 and 30, respectively. Compared to total recovery (Q30), HRQoL loss was 37.5%, 31.5% and 8.9% on days 0, 7 and 14 since diagnosis of the disease. The total median cost per patient (including treatments) was €598.8 (IQR: 359.63–2425.85).

Conclusions

 RSV had almost 40% impact on HRQoL during the first week since onset of symptoms and the median cost per episode and patient was about €600. These results represent a substantial input for health-economic evaluations of future RSV-related interventions such as vaccination.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06629-z.

Cost-utility Analysis of Rotavirus Vaccines Including the Latest Evidence and Data as of June 2020 in Japan

BACKGROUND

In several health economic analyses of rotavirus vaccines in Japan, all were not cost-effective from the healthcare payer perspective (HPP) but generally cost-effective from the societal perspective (SP). However, few studies have incorporated clinically significant factors of vaccine herd immunity, convulsions with gastroenteritis, encephalopathies, nosocomial infections, death, and intussusception as a vaccine side effect. A cost-utility analysis incorporating these were conducted.

METHODS

We used Bakir's decision-tree model and data in Japan with 94% coverage rate, 5-year time horizon, and 2% discount. We compared the incremental cost-effectiveness ratio (ICER) with a willingness-to-pay of Japanese Yen (JPY) 5 million from HPP and SP. Scenario 1 examined items based on existing research; scenario 2 additionally examined the above-mentioned items. In scenario 2, break-even prices were determined, and one-way and probabilistic sensitivity analyses were performed.

RESULTS

In scenario 1, the ICER was JPY 6,057,281 from the HPP and dominant from the SP. In scenario 2, it was JPY 3,713,488 from the HPP. From the HPP in scenario 2, break-even prices were JPY 34,227 for an ICER of JPY 5 million and JPY 17,798 for cost-saving. One-way sensitivity analysis showed ICERs fluctuated widely with ambulatory visits and vaccination costs. In the probabilistic sensitivity analysis, ICERs of 54.8% were less than the willingness-to-pay. In scenario 2, from the SP, vaccines were dominant.

CONCLUSION

From the HPP in scenario 2, the vaccines were cost-effective. In the sensitivity analyses, ICERs also improved from the HPP over previous studies. Herd immunity for ambulatory visits contributed most to the decline.

Modeling of rotavirus transmission dynamics and impact of vaccination in Ghana

Background:

Rotavirus incidence remains relatively high in low-income countries (LICs) compared to high-income countries (HICs) after vaccine introduction. Ghana introduced monovalent rotavirus vaccine in April 2012 and despite the high coverage, vaccine performance has been modest compared to developed countries. The predictors of low vaccine effectiveness in LICs are poorly understood, and the drivers of subnational heterogeneity in rotavirus vaccine impact are unknown.

Methods:

We used mathematical models to investigate variations in rotavirus incidence in children <5 years old in Ghana. We fit models to surveillance and case-control data from three different hospitals: Korle-Bu Teaching Hospital in Accra, Komfo Anokye Teaching Hospital in Kumasi, and War Memorial Hospital in Navrongo. The models were fitted to both pre- and post-vaccine data to estimate parameters describing the transmission rate, waning of maternal immunity, and vaccine response rate.

Results:

The seasonal pattern and age distribution of rotavirus cases varied among the three study sites in Ghana. Our model was able to capture the spatio-temporal variations in rotavirus incidence across the three sites and showed good agreement with the age distribution of observed cases. The rotavirus transmission rate was highest in Accra and lowest in Navrongo, while the estimated duration of maternal immunity was longer (∼5 months) in Accra and Kumasi and shorter (∼3 months) in Navrongo. The proportion of infants who responded to the vaccine was estimated to be high in Accra and Kumasi and low in Navrongo.

Conclusions:

Rotavirus vaccine impact varies within Ghana. A low vaccine response rate was estimated for Navrongo, where rotavirus is highly seasonal and incidence limited to a few months of the year. Our findings highlight the need to further explore the relationship between rotavirus seasonality, maternal immunity, and vaccine response rate to determine how they influence vaccine effectiveness and to develop strategies to improve vaccine impact.

Family Spillover Effects in Pediatric Cost-Utility Analyses

BACKGROUND

Childhood illness can impose significant costs and health strains on family members, but these are not routinely captured by pediatric economic evaluations. This review investigated how family "spillover effects" related to costs and health outcomes are considered in pediatric cost-utility analyses (CUAs).

METHODS

We reviewed pediatric CUAs published between 2000 and 2015 using the Tufts Medical Center Cost-effectiveness Analysis (CEA) Registry and the Pediatric Economic Database Evaluation (PEDE) Registry. We selected studies conducted from the societal perspective and included in both registries. We investigated how frequently family spillover was incorporated into analyses, and how the inclusion of spillover health effects and costs changed CUA results.

RESULTS

We found 142 pediatric CUAs meeting inclusion criteria. Of those, 105 (72%) considered either family spillover costs (n = 98 time costs, n = 33 out-of-pocket costs, n = 2 caregiver healthcare costs) or health outcomes (n = 15). Twenty-four studies included 43 pairs of incremental cost-effectiveness ratios (ICERs) with and without spillover. In 19 pairs of ICERs, adding spillover changed the ICER enough to cross a common cost-effectiveness threshold (i.e., $50,000/QALY, $100,000/QALY, $150,000/QALY; values are in 2016 US$). Incorporating spillover generally made interventions more cost-effective (n = 18; 42%), or did not change CUA results enough to cross a threshold (n = 24; 56%). Including family spillover reduced ICERs by 31% ($40,000/QALY) on average.

CONCLUSION

Most pediatric CUAs conducted from a societal perspective include family costs but fewer include family health effects. Inclusion of family spillover effects tends to make CUA results more favorable. Future pediatric CUAs should aim to more fully incorporate the family burden of illness.

Geographical and Historical Patterns in the Emergences of Novel Highly Pathogenic Avian Influenza (HPAI) H5 and H7 Viruses in Poultry

Over the years, the emergence of novel H5 and H7 highly pathogenic avian influenza viruses (HPAI) has been taking place through two main mechanisms: first, the conversion of a low pathogenic into a highly pathogenic virus, and second, the reassortment between different genetic segments of low and highly pathogenic viruses already in circulation. We investigated and summarized the literature on emerging HPAI H5 and H7 viruses with the aim of building a spatio-temporal database of all these recorded conversions and reassortments events. We subsequently mapped the spatio-temporal distribution of known emergence events, as well as the species and production systems that they were associated with, the aim being to establish their main characteristics. From 1959 onwards, we identified a total of 39 independent H7 and H5 LPAI to HPAI conversion events. All but two of these events were reported in commercial poultry production systems, and a majority of these events took place in high-income countries. In contrast, a total of 127 reassortments have been reported from 1983 to 2015, which predominantly took place in countries with poultry production systems transitioning from backyard to intensive production systems. Those systems are characterized by several co-circulating viruses, multiple host species, regular contact points in live bird markets, limited biosecurity within value chains, and frequent vaccination campaigns that impose selection pressures for emergence of novel reassortants. We conclude that novel HPAI emergences by these two mechanisms occur in different ecological niches, with different viral, environmental and host associated factors, which has implications in early detection and management and mitigation of the risk of emergence of novel HPAI viruses.

Inclusion of the value of herd immunity in economic evaluations of vaccines. A systematic review of methods used

OBJECTIVE

The objectives of this review were to identify vaccine economic evaluations that include herd immunity and describe the methodological approaches used.

METHODS

We used Kim and Goldie's search strategy from a systematic review (1976-2007) of modelling approaches used in vaccine economic evaluations and additionally searched PubMed/MEDLINE and Embase for 2007-2015. Studies were classified according to modelling approach used. Methods for estimating herd immunity effects were described, in particular for the static models.

RESULTS

We identified 625 economic evaluations of vaccines against human-transmissible diseases from 1976 to 2015. Of these, 172 (28%) included herd immunity. While 4% of studies included herd immunity in 2001, 53% of those published in 2015 did this. Pneumococcal, human papilloma and rotavirus vaccines represented the majority of studies (63%) considering herd immunity. Ninety-five of the 172 studies utilised a static model, 59 applied a dynamic model, eight a hybrid model and ten did not clearly state which method was used. Relatively crude methods and assumptions were used in the majority of the static model studies.

CONCLUSION

The proportion of economic evaluations using a dynamic model has increased in recent years. However, 55% of the included studies used a static model for estimating herd immunity. Values from a static model can only be considered reliable if high quality surveillance data are incorporated into the analysis. Without this, the results are questionable and they should only be included in sensitivity analysis.

Re-evaluation of the cost-effectiveness and effects of childhood rotavirus vaccination in Norway

Background

Rotavirus vaccination was included into the Norwegian childhood immunisation programme in 2014. Before implementation, rotavirus vaccination was found to be cost–effective from a societal perspective, but not from a healthcare perspective. Since introduction, new data on the incidence and economic effects of rotavirus disease have become available. We assessed early epidemiological effects of the rotavirus vaccination programme and re–evaluated its cost–effectiveness in Norway for the years 2015–2019.

Methods

Using a dynamic transmission model, we compared the epidemiological effects of the ongoing two–dose vaccination programme with Rotarix^®, and a hypothetical 3–dose programme with RotaTeq^® with no vaccination. A baseline cost of € 54 per fully vaccinated child was used. Cost–effectiveness was computed from a healthcare and societal perspective, using a decision analytical model. Data on healthcare use and costs, productivity losses and health utilities were based on published and own estimates. Uncertainty was accounted for in one–way, multi–way, and probabilistic sensitivity analyses.

Results

During 2015–2019, 114,658 home care cases, 34,571 primary care cases, 7,381 severe cases, and 2 deaths associated with rotavirus disease were avoided due to vaccination. Under baseline assumptions vaccination was cost–effective from a healthcare perspective with a cost per QALY of € 47,447 for Rotarix^® and € 52,709 for RotaTeq^®. The break–even price was € 70 for Rotarix^® and € 67 for RotaTeq^®. Vaccination was cost–saving from the societal perspective, and also from a healthcare perspective for vaccine prices below € 25 and € 22 per vaccinated child for Rotarix^® and RotaTeq^®, respectively.

Conclusion

Ongoing childhood rotavirus vaccination in Norway has reduced the rotavirus disease burden substantially, and is cost–effective compared with no vaccination.

Cost-Effectiveness of Dengue Vaccination Programs in Brazil

The first approved dengue vaccine, CYD-TDV, a chimeric, live-attenuated, tetravalent dengue virus vaccine, was recently licensed in 13 countries, including Brazil. In light of recent vaccine approval, we modeled the cost-effectiveness of potential vaccination policies mathematically based on data from recent vaccine efficacy trials that indicated that vaccine efficacy was lower in seronegative individuals than in seropositive individuals. In our analysis, we investigated several vaccination programs, including routine vaccination, with various vaccine coverage levels and those with and without large catch-up campaigns. As it is unclear whether the vaccine protects against infection or just against disease, our model incorporated both direct and indirect effects of vaccination. We found that in the presence of vaccine-induced indirect protection, the cost-effectiveness of dengue vaccination decreased with increasing vaccine coverage levels because the marginal returns of herd immunity decreases with vaccine coverage. All routine dengue vaccination programs that we considered were cost-effective, reducing dengue incidence significantly. Specifically, a routine dengue vaccination of 9-year-olds would be cost-effective when the cost of vaccination per individual is less than $262. Furthermore, the combination of routine vaccination and large catch-up campaigns resulted in a greater reduction of dengue burden (by up to 93%) than routine vaccination alone, making it a cost-effective intervention as long as the cost per course of vaccination is $255 or less. Our results show that dengue vaccination would be cost-effective in Brazil even with a relatively low vaccine efficacy in seronegative individuals.

Global economic evaluations of rotavirus vaccines: A systematic review

INTRODUCTION

World Health Organization (WHO) recommends Rotavirus vaccines to prevent and control rotavirus infections. Economic evaluations (EE) have been considered to support decision making of national policy. Summarizing global experience of the economic value of rotavirus vaccines is crucial in order to encourage global WHO recommendations for vaccine uptake. Therefore, a systematic review of economic evaluations of rotavirus vaccine was conducted.

METHODS

We searched Medline, Embase, NHS EED, EconLit, CEA Registry, SciELO, LILACS, CABI-Global Health Database, Popline, World Bank - e-Library, and WHOLIS. Full economic evaluations studies, published from inception to November 2015, evaluating Rotavirus vaccines preventing Rotavirus infections were included. The methods, assumptions, results and conclusions of the included studies were extracted and appraised using WHO guide for standardization of EE of immunization programs.

RESULTS

104 relevant studies were included. The majority of studies were conducted in high-income countries. Cost-utility analysis was mostly reported in many studies using incremental cost-effectiveness ratio per DALY averted or QALY gained. Incremental cost per QALY gained was used in many studies from high-income countries. Mass routine vaccination against rotavirus provided the ICERs ranging from cost-saving to highly cost-effective in comparison to no vaccination among low-income countries. Among middle-income countries, vaccination offered the ICERs ranging from cost-saving to cost-effective. Due to low- or no subsidized price of rotavirus vaccines from external funders, being not cost-effective was reported in some high-income settings.

CONCLUSION

Mass vaccination against rotavirus was generally found to be cost-effective, particularly in low- and middle-income settings according to the external subsidization of vaccine price. On the other hand, it may not be a cost-effective intervention at market price in some high-income settings. This systematic review provides supporting information to health policy-makers and health professionals when considering rotavirus vaccination as a national program.

Dengue Dynamics and Vaccine Cost-Effectiveness Analysis in the Philippines

Dengue is one of the most problematic vector-borne diseases in the Philippines, with an estimated 842,867 cases resulting in medical costs of $345 million U.S. dollars annually. In December 2015, the first dengue vaccine, known as chimeric yellow fever virus-dengue virus tetravalent dengue vaccine, was approved for use in the Philippines and is given to children 9 years of age. To estimate the cost-effectiveness of dengue vaccination in the Philippines, we developed an age-structured model of dengue transmission and vaccination. Using our model, we compared two vaccination scenarios entailing routine vaccination programs both with and without catch-up vaccination. Our results indicate that the higher the cost of vaccination, the less cost-effective the dengue vaccination program. With the current dengue vaccination program that vaccinates children 9 years of age, dengue vaccination is cost-effective for vaccination costs up to $70 from a health-care perspective and up to $75 from a societal perspective. Under a favorable scenario consisting of 1 year of catch-up vaccinations that target children 9-15 years of age, followed by regular vaccination of 9-year-old children, vaccination is cost-effective at costs up to $72 from a health-care perspective and up to $78 from a societal perspective. In general, dengue vaccination is expected to reduce the incidence of both dengue fever and dengue hemorrhagic fever /dengue shock syndrome. Our results demonstrate that even at relatively low vaccine efficacies, age-targeted vaccination may still be cost-effective provided the vaccination cost is sufficiently low.

Time series investigation of changes in seasonality of acute diarrhea hospitalizations before and after rotavirus vaccine in Southern Brazil

Diarrhea by rotavirus is one of the main causes of mortality in children in developing countries, although the hospitalization rates (HR) for acute diarrhea have been found to have fallen since the introduction of the rotavirus vaccine. However, the patterns of the rotavirus are still not well understood and seasonal peaks occur throughout the year, with variations between countries and over time. The main objective of this study was to analyze the temporal behavior of HR caused by acute diarrhea in children under the age of one in the south of Brazil, between 2000 and 2011, and to explore changes in seasonality patters after the introduction of the vaccine against the rotavirus in 2006. Harmonic and multiscale wavelet analyses were used to detect seasonality and the points of change in the temporal scale. The statistical significance of each seasonality that was identified was tested using Fisher's test. The harmonic and wavelet analyses show annual seasonal and six-monthly patterns for HR, as well as a clear change after the introduction of the vaccine in 2006.

Cost Effectiveness of Influenza Vaccine for U.S. Children: Live Attenuated and Inactivated Influenza Vaccine

INTRODUCTION

Prior studies showed that live attenuated influenza vaccine (LAIV) is more effective than inactivated influenza vaccine (IIV) in children aged 2-8 years, supporting the Centers for Disease Control and Prevention (CDC) recommendations in 2014 for preferential LAIV use in this age group. However, 2014-2015 U.S. effectiveness data indicated relatively poor effectiveness of both vaccines, leading CDC in 2015 to no longer prefer LAIV.

METHODS

An age-structured model of influenza transmission and vaccination was developed, which incorporated both direct and indirect protection induced by vaccination. Based on this model, the cost effectiveness of influenza vaccination strategies in children aged 2-8 years in the U.S. was estimated. The base case assumed a mixed vaccination strategy where 33.3% and 66.7% of vaccinated children aged 2-8 years receive LAIV and IIV, respectively. Analyses were performed in 2014-2015.

RESULTS

Using published meta-analysis vaccine effectiveness data (83% LAIV and 64% IIV), exclusive LAIV use would be a cost-effective strategy when vaccinating children aged 2-8 years, whereas IIV would not be preferred. However, when 2014-2015 U.S. effectiveness data (0% LAIV and 15% IIV) were used, IIV was likely to be preferred.

CONCLUSIONS

The cost effectiveness of influenza vaccination in children aged 2-8 years is highly dependent on vaccine effectiveness; the vaccine type with higher effectiveness is preferred. In general, exclusive IIV use is preferred over LAIV use, as long as vaccine effectiveness is higher for IIV than for LAIV.

A multifactorial regression analysis of the features of community-acquired rotavirus requiring hospitalization in Spain as represented in the Minimum Basic Data Set

Over 10% of acute rotavirus gastroenteritis (ARGE) requires hospitalization because of complications. The aggravating factors have been widely analysed, but in an isolated way. We aimed to explore the interrelationship between the clinical and epidemiological factors that characterize rotavirus hospitalizations in Spain using information from the Minimum Basic Data Set (MBDS). Using ICD-9-CM codes, we classified acute gastroenteritis (AGE) cases by principal diagnosis fields and then categorized their comorbidities, complications, and epidemiological features by secondary fields. A multivariable, logistic, step-wise regression model was then constructed. We identified 1657 ARGE cases from 17 415 cases of AGE. Rotavirus hospitalizations were associated with place of residence, age, and season (P < 0·0001), as well as with dehydration [odds ratio (OR) 12·44, 95% confidence interval (CI) 1·52-40·38], intravenous rehydration (OR 1·74, 95% CI 1·29-2·35), metabolic acidosis (OR 1·51, 95% CI 1·24-1·83), respiratory tract infections (RTIs) (OR 1·60, 95% CI 1·09-1·98), and concomitant AGE (OR 1·52, 95% CI 1·03-2·25). Dehydration was four times more likely in patients aged <5 years (OR 4·36, 95% CI 1·20-12·96) and was associated with acidosis when ARGE and RTI were present simultaneously (P < 0·0001). Specific co-infecting viruses may play a role in acute respiratory symptoms and aggravation of gastrointestinal manifestations of rotaviruses, thus leading to complications requiring hospitalization.

Cost-Effectiveness of Rotavirus Vaccination in France-Accounting for Indirect Protection

BACKGROUND

Vaccination against rotavirus has shown great potential for reducing the primary cause of severe childhood gastroenteritis. Previous economic evaluations of rotavirus vaccination in France have not modeled the potential impact of vaccines on disease burden via reduced transmission.

OBJECTIVE

To determine the cost-effectiveness of the introduction of pentavalent rotavirus vaccination into the French infant vaccination schedule.

METHODS

We developed an age-structured model of rotavirus transmission calibrated to 6 years of French gastroenteritis incidence and vaccine clinical trial data. We evaluated the cost-effectiveness of pentavalent rotavirus vaccination considering that 75% of infants would receive the three-dose vaccine course.

RESULTS

Our model predicts that rotavirus vaccination will decrease rotavirus gastroenteritis incidence and associated clinical outcomes in vaccinated and unvaccinated individuals, delay the seasonal peak of infection, and increase the age of infection. From the societal perspective, our base-case scenario predicts that vaccination coverage would be cost-effective at €115 or €135 per vaccine course at €28,500 and €39,500/quality-adjusted life-year (QALY) gained, respectively, and suggests that almost 95% of the financial benefits will be recouped within the first 5 years following vaccination implementation. From the third-party payer perspective, incremental cost-effectiveness ratios ranged from €12,500 to €20,000/QALY, respectively. Our uncertainty analysis suggests that findings were sensitive to various assumptions including the number of hospitalizations, outpatient visits, and the extent of QALY losses per rotavirus episode.

CONCLUSIONS

Introducing pentavalent rotavirus vaccination into the French infant vaccination schedule would significantly reduce the burden of rotavirus disease in children, and could be cost-effective under plausible conditions.

Economic evaluation of pediatric influenza immunization program compared with other pediatric immunization programs: A systematic review

This study compared the economic value of pediatric immunisation programmes for influenza to those for rotavirus (RV), meningococcal disease (MD), pneumococcal disease (PD), human papillomavirus (HPV), hepatitis B (Hep B), and varicella reported in recent (2000 onwards) cost-effectiveness (CE) studies identified in a systematic review of PubMed, health technology, and vaccination databases. The systematic review yielded 51 economic evaluation studies of pediatric immunisation - 10 (20%) for influenza and 41 (80%) for the other selected diseases. The quality of the eligible articles was assessed using Drummond's checklist. Although inherent challenges and limitations exist when comparing economic evaluations of immunisation programmes, an overall comparison of the included studies demonstrated cost-effectiveness/cost saving for influenza from a European-Union-Five (EU5) and United States (US) perspective; point estimates for cost/quality-adjusted life-years (QALY) from dominance (cost-saving with more effect) to ≤45,444 were reported. The economic value of influenza programmes was comparable to the other vaccines of interest, with cost/QALY in general considerably lower than RV, Hep B, MD and PD. Independent of the perspective and type of analysis, the economic impact of a pediatric influenza immunisation program was influenced by vaccine efficacy, immunisation coverage, costs, and most significantly by herd immunity. This review suggests that pediatric influenza immunisation may offer a cost effective strategy when compared with HPV and varicella and possibly more value compared with other childhood vaccines (RV, Hep B, MD and PD).

Sources and Characteristics of Utility Weights for Economic Evaluation of Pediatric Vaccines: A Systematic Review

BACKGROUND

Cost-effectiveness analysis of pediatric vaccines for infectious diseases often requires quality-of-life (utility) weights.

OBJECTIVE

To investigate how utility weights have been elicited and used in this context.

METHODS

A systematic review was conducted of studies published between January 1990 and July 2013 that elicited or used utility weights in cost-effectiveness analyses of vaccines for pediatric populations. The review focused on vaccines for 17 infectious diseases and is presented following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) methodology.

RESULTS

A total of 6410 titles and abstracts and 225 full-text articles were reviewed. Of those selected for inclusion (n = 101), 15 articles described the elicitation of utility weights and 86 described economic modeling studies using utilities. Various methods were used to generate utilities, including time trade-off, contingent valuation, and willingness to pay, as well as a preference-based measure with associated value sets, such as the EuroQol five-dimensional questionnaire or the Health Utilities Index. In modeling studies, the source of utilities used was often unclear, poorly reported, or based on weak underlying evidence. We found no articles that reported on the elicitation or use of utilities in diphtheria, polio, or tetanus.

CONCLUSIONS

The scarcity of appropriate utility weights for vaccine-preventable infectious diseases in children and a lack of standardization in their use in economic assessments limit the ability to accurately assess the benefits associated with interventions to prevent infectious diseases. This is an issue that should be of concern to those making decisions regarding the prevention and treatment of infectious childhood illnesses.

Vaccination Programs for Endemic Infections: Modelling Real versus Apparent Impacts of Vaccine and Infection Characteristics

Vaccine effect, as measured in clinical trials, may not accurately reflect population-level impact. Furthermore, little is known about how sensitive apparent or real vaccine impacts are to factors such as the risk of re-infection or the mechanism of protection. We present a dynamic compartmental model to simulate vaccination for endemic infections. Several measures of effectiveness are calculated to compare the real and apparent impact of vaccination, and assess the effect of a range of infection and vaccine characteristics on these measures. Although broadly correlated, measures of real and apparent vaccine effectiveness can differ widely. Vaccine impact is markedly underestimated when primary infection provides partial natural immunity, when coverage is high and when post-vaccination infectiousness is reduced. Despite equivalent efficacy, 'all or nothing' vaccines are more effective than 'leaky' vaccines, particularly in settings with high risk of re-infection and transmissibility. Latent periods result in greater real impacts when risk of re-infection is high, but this effect diminishes if partial natural immunity is assumed. Assessments of population-level vaccine effects against endemic infections from clinical trials may be significantly biased, and vaccine and infection characteristics should be considered when modelling outcomes of vaccination programs, as their impact may be dramatic.

Qualitative Effects of Monovalent Vaccination Against Rotavirus: A Comparison of North America and South America

Rotavirus is the most common cause of severe gastroenteritis in young children worldwide. The introduction of vaccination programs has led to a significant reduction in number of hospitalizations due to rotavirus in North and South American countries. Little work has been done, however, to examine the differential impact of vaccination as a function of strain distribution and strain-specific vaccine efficacy. We developed a two-strain epidemiological model of rotavirus transmission, and used it to examine the effects of a monovalent vaccine (Rotarix) on the qualitative behaviors of infection levels in a population. For contrast, we parameterized our model with strain distribution data from North America and from South America. In all cases, the introduction of the vaccine led to significant decreases in the prevalence of primary infection due to both strains for a decade or more, after which the overall prevalence recovers to near pre-vaccination levels. The prevalence of G1P[8] is significantly higher in North America (73 % of all rotavirus infections) compared to that in South America (34 %). Our model predicts that the introduction of Rotarix might result in major strain replacement in regions such as North America where the prevalence of G1P[8] is relatively high, due to higher efficacy of Rotarix against infection caused by G1P[8], while regions with lower prevalence of G1P[8], such as South America, are not susceptible to major strain replacement.

Dissecting the indirect effects caused by vaccines into the basic elements

Vaccination directly protects vaccinated individuals, but it also has the potential for indirectly protecting the unvaccinated in a population (herd protection). Unintended negative consequences such as the re-manifestation of infection, mainly expressed as age shifts, result from vaccination programs as well. We discuss the necessary conditions for achieving optimal herd protection (i.e., high quality vaccine-induced immunity, substantial effect on the force of infection, and appropriate vaccine coverage and distribution), as well as the conditions under which age shifts are likely to occur. We show examples to illustrate these effects. Substantial ambiguity in observing and quantifying these indirect vaccine effects makes accurate evaluation troublesome even though the nature of these outcomes may be critical for accurate assessment of the economic value when decision makers are evaluating a novel vaccine for introduction into a particular region or population group. More investigation is needed to identify and develop successful assessment methodologies for precisely analyzing these outcomes.

Quantifying Parameter and Structural Uncertainty of Dynamic Disease Transmission Models Using MCMC: An Application to Rotavirus Vaccination in England and Wales

BACKGROUND

Two vaccines (Rotarix and RotaTeq) are highly effective at preventing severe rotavirus disease. Rotavirus vaccination has been introduced in the United Kingdom and other countries partly based on modeling and cost-effectiveness results. However, most of these models fail to account for the uncertainty about several vaccine characteristics and the mechanism of vaccine action.

METHODS

A deterministic dynamic transmission model of rotavirus vaccination in the United Kingdom was developed. This improves on previous models by 1) allowing for 2 different mechanisms of action for Rotarix and RotaTeq, 2) using clinical trial data to understand these mechanisms, and 3) accounting for uncertainty by using Markov Chain Monte Carlo.

RESULTS

In the long run, Rotarix and RotaTeq are predicted to reduce the overall rotavirus incidence by 50% (39%-63%) and 44% (30%-62%), respectively but with an increase in incidence in primary school children and adults up to 25 y of age. The vaccines are estimated to give more protection than 1 or 2 natural infections. The duration of protection is highly uncertain but has only impact on the predicted reduction in rotavirus burden for values lower than 10 y. The 2 vaccine mechanism structures fit equally well with the clinical trial data. Long-term postvaccination dynamics cannot be predicted reliably with the data available.

CONCLUSION

Accounting for the joint uncertainty of several vaccine characteristics resulted in more insight into which of these are crucial for determining the impact of rotavirus vaccination. Data for up to at least 10 y postvaccination and covering older children and adults are crucial to address remaining questions on the impact of widespread rotavirus vaccination.

Bayesian parameter inference for dynamic infectious disease modelling: rotavirus in Germany

Understanding infectious disease dynamics using epidemic models based on ordinary differential equations requires the calibration of model parameters from data. A commonly used approach in practice to simplify this task is to fix many parameters on the basis of expert or literature information. However, this not only leaves the corresponding uncertainty unexamined but often also leads to biased inference for the remaining parameters because of dependence structures inherent in any given model. In the present work, we develop a Bayesian inference framework that lessens the reliance on such external parameter quantifications by pursuing a more data-driven calibration approach. This includes a novel focus on residual autocorrelation combined with model averaging techniques in order to reduce these estimates' dependence on the underlying model structure. We applied our methods to the modelling of age-stratified weekly rotavirus incidence data in Germany from 2001 to 2008 using a complex susceptible-infectious-susceptible-type model complemented by the stochastic reporting of new cases. As a result, we found the detection rate in the eastern federal states to be more than four times higher compared with that of the western federal states (19.0% vs 4.3%), and also the infectiousness of symptomatically infected individuals was estimated to be more than 10 times higher than that of asymptomatically infected individuals (95% credibility interval: 8.1–19.6). Not only do these findings give valuable epidemiological insight into the transmission processes, we were also able to examine the considerable impact on the model-predicted transmission dynamics when fixing parameters beforehand.

Dynamic modeling of cost-effectiveness of rotavirus vaccination, Kazakhstan

The government of Kazakhstan, a middle-income country in Central Asia, is considering the introduction of rotavirus vaccination into its national immunization program. We performed a cost-effectiveness analysis of rotavirus vaccination spanning 20 years by using a synthesis of dynamic transmission models accounting for herd protection. We found that a vaccination program with 90% coverage would prevent ≈880 rotavirus deaths and save an average of 54,784 life-years for children <5 years of age. Indirect protection accounted for 40% and 60% reduction in severe and mild rotavirus gastroenteritis, respectively. Cost per life year gained was US $18,044 from a societal perspective and US $23,892 from a health care perspective. Comparing the 2 key parameters of cost-effectiveness, mortality rates and vaccine cost at <US $2.78 per dose, vaccination program costs would be entirely offset. To further evaluate efficacy of a vaccine program, benefits of indirect protection conferred by vaccination warrant further study.

Systematic review of the economic value of diarrheal vaccines

Diarrheal disease is a leading cause of child mortality in low-income settings and morbidity across a range of settings. A growing number of studies have addressed the economic value of new and emerging vaccines to reduce this threat. We conducted a systematic review to assess the economic value of diarrheal vaccines targeting a range of pathogens in different settings. The majority of studies focused on the economic value of rotavirus vaccines in different settings, with most of these concluding that vaccination would provide significant economic benefits across a range of vaccine prices. There is also evidence of the economic benefits of cholera vaccines in specific contexts. For other potential diarrheal vaccines data are limited and often hypothetical. Across all target pathogens and contexts, the evidence of economic value focuses the short-term health and economic gains. Additional information is needed on the broader social and long-term economic value of diarrhea vaccines.

Systematic review of incremental non-vaccine cost estimates used in cost-effectiveness analysis on the introduction of rotavirus and pneumococcal vaccines

OBJECTIVE

To review the approaches used in the cost-effectiveness analysis (CEAs) literature to estimate the cost of expanded program on immunization (EPI) activities, other than vaccine purchase, for rotavirus and pneumococcal vaccines.

METHODS

A systematic review in PubMed and NHS EED databases of rotavirus and pneumococcal vaccines CEAs was done. Selected articles were read and information on how EPI costs were calculated was extracted. EPI costing approaches were classified according to the method or assumption used for estimation.

RESULTS

Seventy-nine studies that evaluated cost effectiveness of rotavirus (n=43) or pneumococcal (n=36) vaccines were identified. In general, there are few details on how EPI costs other than vaccine procurement were estimated. While 30 studies used some measurement of that cost, only one study on pneumococcal vaccine used a primary cost evaluation (bottom-up costing analysis) and one study used a costing tool. Twenty-seven studies (17 on rotavirus and 10 on pneumococcal vaccine) assumed the non-vaccine costs. Five studies made no reference to additional costs. Fourteen studies (9 rotavirus and 5 pneumococcal) did not consider any additional EPI cost beyond vaccine procurement. For rotavirus studies, the median for non-vaccine cost per dose was US$0.74 in developing countries and US$6.39 in developed countries. For pneumococcal vaccines, the median for non-vaccine cost per dose was US$1.27 in developing countries and US$8.71 in developed countries.

CONCLUSIONS

Many pneumococcal (52.8%) and rotavirus (60.4%) cost-effectiveness analyses did not consider additional EPI costs or used poorly supported assumptions. Ignoring EPI costs in addition to those for vaccine procurement in CEA analysis of new vaccines may lead to significant errors in the estimations of ICERs since several factors like personnel, cold chain, or social mobilization can be substantially affected by the introduction of new vaccines.

Respiratory syncytial virus immunization program for the United States: impact of performance determinants of a theoretical vaccine

OBJECTIVES

To inform strategic decisions on respiratory syncytial virus (RSV) vaccine development and identify critical endpoints likely to drive the vaccine's medical and economic impact.

DESIGN

A decision-analysis model populated using healthcare utilization data and costs from the literature; vaccine efficacy and duration based on assumptions.

SETTING

Vaccination in the physician office setting in the USA.

PARTICIPANTS

A hypothetical cohort of newborn infants.

INTERVENTION

Vaccination of children at low and high risk of respiratory sequelae with a theoretical RSV vaccine vs palivizumab prophylaxis for children at high risk.

OUTCOME MEASURES

Medical and economic value of RSV vaccination, including cost per quality adjusted life-year (QALY) gained.

RESULTS

Using base-case assumptions (efficacy 50% at birth; half-life 12 months), RSV vaccination would prevent 23,069 hospitalizations and 66 deaths per vaccinated birth cohort in the USA. Excluding vaccination costs, direct medical costs for RSV would reduce by $236 million, and income and productivity losses by $134 million. Assuming a vaccine cost per course similar to Rotarix® in the USA ($232 including administration fees), the cost per QALY gained would be $93,401 (95% CI: $65,815-$126,060) from the healthcare system perspective and $65,115 (95% CI: $41,003-$93,679) from the societal perspective. The net cost (healthcare system perspective) per life-year saved would be $216,120 (95% CI: $161,184-$263,981); the cost per hospitalization averted would be $19,172 (95% CI: $14,679-$22,093). Aside from efficacy, the vaccine's impact is sensitive to the start of protective immunity and the duration of protection.

CONCLUSIONS

Development of an RSV vaccine would substantially reduce inpatient hospitalizations and outpatient visits. It would also have an impact on infant mortality. To demonstrate the full medical and economic value of the vaccine, appropriate endpoints or endpoint surrogates for hospitalization, mortality, and total case reductions should be collected during vaccine development.

A critical literature review of health economic evaluations of rotavirus vaccination

Two licensed vaccines are available to prevent RVGE in infants. A worldwide critical review of economic evaluations of these vaccines was conducted. The objective was to describe differences in methodologies, assumptions and inputs and determine the key factors driving differences in conclusions. 68 economic evaluations were reviewed. RV vaccination was found to be cost-effective in developing countries, while conclusions varied between studies in developed countries. Many studies found that vaccination was likely to be cost-effective under some scenarios, such as lower prices scenarios, inclusion of herd protection, and/or adoption of a societal perspective. Other reasons for variability included uncertainty around healthcare visits incidence and lack of consensus on quality of life (QoL) valuation for infants and caregivers. New evidence on the vaccination effectiveness in real-world, new ways of modeling herd protection and assessments of QoL in children could help more precisely define the conditions under which RV vaccination would be cost-effective in developed countries.

Categorization of methods used in cost-effectiveness analyses of vaccination programs based on outcomes from dynamic transmission models

The aim of this study is to categorize methods used to estimate the cost-effectiveness of vaccination programs using dynamic transmission models, and assess value to decision-makers. A targeted literature search of PubMed has been carried out for this purpose. A review of 43 articles presenting cost-effectiveness analyses of vaccination programs based on dynamic transmission models identified four methods for the estimation of a cost-effectiveness ratio: cumulative population values over a fixed time horizon; population values for a steady-state year; cohort values from time of program initiation; and cohort values at steady state. Cost-effectiveness estimates are sensitive to the choice of time horizon or number of cohorts included. Estimates at steady state are the most comparable to estimates for other healthcare interventions but do not account for pre-steady-state periods. Population values provide estimates of budget impact. In conclusion, four different methods were identified for converting clinical outcomes from a dynamic transmission model to cost-effectiveness estimates. Sensitivity analyses for time horizon or number of cohorts considered should be routinely performed.

Laboratory-Confirmed Rotavirus Disease in Utah Children: Clinical and Economic Impact of Rotavirus Vaccination

BACKGROUND

Rotavirus is the most common cause of infectious diarrhea in children worldwide. Recent studies have described changes in the burden of all-cause gastroenteritis; however, there are limited data on the clinical and economic impact of rotavirus vaccine on cases of laboratory-confirmed rotavirus disease.

METHODS

We performed a retrospective study of laboratory-confirmed rotavirus disease from July 2003 through June 2010 at a children's hospital and a community hospital in Utah. Demographics and hospital costs for children <5 years with rotavirus symptoms and a positive rotavirus enzyme immunoassay test on a stool specimen were abstracted from electronic medical records. We compared the prevaccine period (2003-2007) with the postvaccine period (2008-2010).

RESULTS

The overall incidence of rotavirus gastroenteritis declined in the postvaccine period, from 26.6 to 5.2 cases per 10 000 person-years for Salt Lake County residents. The largest decrease in the incidence of rotavirus gastroenteritis was among children <12 months (-87%; 95% confidence interval [CI], 79-93). Older children (12-23 months) also experienced significant decreases (-81%; 95% CI, 72-88), as did those 24-59 months (-61%; 95% CI, 51-71). In 2009, 3 years after rotavirus vaccine introduction, there was a 79% decrease in emergency department visits and a 78% decrease in hospitalizations across both hospitals. The cost of emergency department visits and hospitalizations for rotavirus gastroenteritis decreased by 79% and 72%, respectively, resulting in annual savings of $790 000 at a children's hospital and $140 000 at a community hospital.

CONCLUSION

Rotavirus vaccination in infants has dramatically decreased the clinical burden and direct medical costs of rotavirus gastroenteritis in both infants and young children.

Distinguishing vaccine efficacy and effectiveness

BACKGROUND

Mathematical models of disease transmission and vaccination typically assume that protective vaccine efficacy (i.e. the relative reduction in the transmission rate among vaccinated individuals) is equivalent to direct effectiveness of vaccine. This assumption has not been evaluated.

METHODS

We used dynamic epidemiological models of influenza and measles vaccines to evaluate the common measures of vaccine effectiveness in terms of both the protection of individuals and disease control within populations. We determined how vaccine-mediated reductions in attack rates translate into vaccine efficacy as well as into the common population measures of 'direct', 'indirect', 'total', and 'overall' effects of vaccination with examples of compartmental models of influenza and measles vaccination.

RESULTS

We found that the typical parameterization of vaccine efficacy using direct effectiveness of vaccine can lead to the underestimation of the impact of vaccine. Such underestimation occurs when the vaccine is assumed to offer partial protection to every vaccinated person, and becomes worse when the level of vaccine coverage is low. Nevertheless, estimates of 'total', 'indirect' and 'overall' effectiveness increase with vaccination coverage in the population. Furthermore, we show how the measures of vaccine efficacy and vaccine effectiveness can be correctly calculated.

CONCLUSIONS

Typical parameterization of vaccine efficacy in mathematical models may underestimate the actual protective effect of the vaccine, resulting in discordance between the actual effects of vaccination at the population level and predictions made by models. This work shows how models can be correctly parameterized from clinical trial data.

Direct and indirect effects of rotavirus vaccination: comparing predictions from transmission dynamic models

Early observations from countries that have introduced rotavirus vaccination suggest that there may be indirect protection for unvaccinated individuals, but it is unclear whether these benefits will extend to the long term. Transmission dynamic models have attempted to quantify the indirect protection that might be expected from rotavirus vaccination in developed countries, but results have varied. To better understand the magnitude and sources of variability in model projections, we undertook a comparative analysis of transmission dynamic models for rotavirus. We fit five models to reported rotavirus gastroenteritis (RVGE) data from England and Wales, and evaluated outcomes for short- and long-term vaccination effects. All of our models reproduced the important features of rotavirus epidemics in England and Wales. Models predicted that during the initial year after vaccine introduction, incidence of severe RVGE would be reduced 1.8–2.9 times more than expected from the direct effects of the vaccine alone (28–50% at 90% coverage), but over a 5-year period following vaccine introduction severe RVGE would be reduced only by 1.1–1.7 times more than expected from the direct effects (54–90% at 90% coverage). Projections for the long-term reduction of severe RVGE ranged from a 55% reduction at full coverage to elimination with at least 80% coverage. Our models predicted short-term reductions in the incidence of RVGE that exceeded estimates of the direct effects, consistent with observations from the United States and other countries. Some of the models predicted that the short-term indirect benefits may be offset by a partial shifting of the burden of RVGE to older unvaccinated individuals. Nonetheless, even when such a shift occurs, the overall reduction in severe RVGE is considerable. Discrepancies among model predictions reflect uncertainties about age variation in the risk and reporting of RVGE, and the duration of natural and vaccine-induced immunity, highlighting important questions for future research.

Application of classic utilities to published pediatric cost-utility studies

OBJECTIVE

Economic analyses, such as cost-utility analyses (CUAs), are dependent on the quality of the data used. Our objective was to test how health utility values (measurements of patient preference) assessed by recommended methods (classic utilities) would impact the conclusions in published pediatric CUAs.

METHODS

Classic utilities for pediatric health states were obtained by recommended utility assessment methods, time trade-off, and standard gamble in 4016 parent interviews. To test the impact of these utilities on published studies, we obtained a sample of published pediatric CUAs by searching Medline, EMBASE, EconLit, Health Technology Assessment Database, Cochrane Database on Systematic Reviews, Database of Abstracts of Reviews of Effects, and the Cost Effective Analysis (CEA) Registry at Tufts Medical Center, using search terms for cost-utility analysis. Articles were included when results were presented as cost per quality adjusted life-years (QALYs), the interventions were for children <18 years of age and included at least one of the following health states: attention deficit hyperactivity disorder, asthma, gastroenteritis, hearing loss, mental retardation, otitis media, seizure disorder, or vision loss. Studies that did not include these or equivalent health states were excluded. For each CUA, we determined utilities (values for patient preference), the utility assessment method used, and presence of one-way sensitivity analyses (SAs) on utilities. When one-way SAs were conducted, we determined if using our classic utilities would change the result of the CUA. When an SA was not presented, we determined if using our classic utilities would tend to support or not support the published conclusions.

RESULTS

We evaluated 39 articles. Eighteen articles presented results of one-way SAs on utilities. Seven articles presented SAs over a range that included our classic utilities. In 4 of the 7, using classic utilities would change the conclusion of the study. For the 32 articles where no one-way SA were presented (n = 21), or where the classic utilities fell outside the range tested (n =11), a change to classic utility would tend against the study conclusion in 12 articles (31%).

CONCLUSIONS

More than a third of published CUA studies could change if pediatric utilities obtained by recommended, classic methods were used. One-way SAs on utilities are often not presented, making comparison between studies challenging.

Cost-effectiveness analysis of palivizumab among pre-term infant populations covered by Medicaid in the United States

OBJECTIVE

Medicaid infants are at high risk of severe respiratory syncytial virus (RSV) disease. The study objective was to estimate the cost-effectiveness of palivizumab in a Medicaid population.

METHODS

A societal cost-utility analysis was conducted of prophylaxis with palivizumab vs no prophylaxis among four groups of premature infants: (1) <32 weeks gestational age (wGA) and ≤ 6 months chronologic age (CA); (2) 32-34 wGA, ≤ 3 months CA with 2009 American Academy of Pediatrics (AAP) risk factors (RF); (3) 32-35 wGA, ≤ 6 months CA with 2006 AAP RF; and (4) 32-35 wGA, ≤ 6 months CA with ≤ 1 RF. Full dosing of palivizumab was assumed throughout the RSV season (consistent with the FDA-approved label). All costs were in 2010 US dollars. The societal public payer spend for palivizumab was estimated using Medicaid reimbursement methodologies for the top 10 palivizumab-using states in 2010 minus mandatory manufacturer rebates. This study reports the incremental cost-effectiveness ratios (ICERs) in cost per quality-adjusted life-year (QALY) gained. Sensitivity and probabilistic analyses were also conducted.

RESULTS

Palivizumab saved costs and improved QALYs among infants <32 wGA. Palivizumab was cost-effective in infants 32-34 wGA with 2009 AAP RF ($16,037 per QALY) and in infants 32-35 wGA with 2006 AAP RF ($38,244 per QALY). The ICER for infants 32-35 wGA with ≤ 1 RF was $281,892 per QALY. Influential variables in the sensitivity analysis included the background rate of RSV hospitalization, the cost of palivizumab, and the efficacy of palivizumab.

KEY LIMITATIONS

These results are not generalizable to commercially insured infants or infants outside of the US.

CONCLUSIONS

This is the first cost-utility analysis of palivizumab in a Medicaid population. Palivizumab, when dosed consistent with the FDA-approved labeling, was either cost-saving or cost-effective among current guideline-eligible infants in the Medicaid population. Palivizumab did not demonstrate cost-effectiveness in 32-35 wGA infants with ≤ 1 RF.

Modeling rotavirus strain dynamics in developed countries to understand the potential impact of vaccination on genotype distributions

Understanding how immunity shapes the dynamics of multistrain pathogens is essential in determining the selective pressures imposed by vaccines. There is currently much interest in elucidating the strain dynamics of rotavirus to determine whether vaccination may lead to the replacement of vaccine-type strains. In developed countries, G1P[8] strains constitute the majority of rotavirus infections most years, but occasionally other genotypes dominate for reasons that are not well understood. We developed a mathematical model to examine the interaction of five common rotavirus genotypes. We explored a range of estimates for the relative strength of homotypic vs. heterotypic immunity and compared model predictions against observed genotype patterns from six countries. We then incorporated vaccination in the model to examine its impact on rotavirus incidence and the distribution of strains. Our model can explain the coexistence and cyclical pattern in the distribution of genotypes observed in most developed countries. The predicted frequency of cycling depends on the relative strength of homotypic vs. heterotypic immunity. Vaccination that provides strong protection against G1 and weaker protection against other strains will likely lead to an increase in the relative prevalence of non-G1 strains, whereas a vaccine that provides equally strong immunity against all strains may promote the continued predominance of G1. Overall, however, disease incidence is expected to be substantially reduced under both scenarios and remain below prevaccination levels despite the possible emergence of new strains. Better understanding of homotypic vs. heterotypic immunity, both natural and vaccine-induced, will be critical in predicting the impact of vaccination.

Rotavirus vaccine RIX4414 (Rotarix™): a pharmacoeconomic review of its use in the prevention of rotavirus gastroenteritis in developing countries

This article provides an overview of the clinical profile of rotavirus vaccine RIX4414 (Rotarix™) in the prevention of rotavirus gastroenteritis (RVGE) in developing countries, followed by a comprehensive review of pharmacoeconomic analyses with the vaccine in low- and middle-income countries. RVGE is associated with significant morbidity and mortality among children <5 years of age in developing countries. The protective efficacy of a two-dose oral series of rotavirus vaccine RIX4414 has been demonstrated in several well designed clinical trials conducted in developing countries, and the 'real-world' effectiveness of the vaccine has also been shown in naturalistic and case-control trials after the introduction of universal vaccination programmes with RIX4414 in Latin American countries. The WHO recommends universal rotavirus vaccination programmes for all countries. Numerous modelled cost-effectiveness analyses have been conducted with rotavirus vaccine RIX4414 across a wide range of low- and middle-income countries. Although data sources and assumptions varied across studies, results of the analyses consistently showed that the introduction of the vaccine as part of a national vaccination programme would be very (or highly) cost effective compared with no rotavirus vaccination programme, according to widely used cost-effectiveness thresholds for developing countries. Vaccine price was not known at the time the analyses were conducted and had to be estimated. In sensitivity analyses, rotavirus vaccine RIX4414 generally remained cost effective at the highest of a range of possible vaccine prices considered. Despite these favourable results, decisions regarding the implementation of universal vaccination programmes with RIX4414 may also be contingent on budgetary and other factors, underscoring the importance of subsidized vaccination programmes for poor countries through the GAVI Alliance (formerly the Global Alliance for Vaccines and Immunization).

Use of models to identify cost-effective interventions: pertussis vaccination for pediatric health care workers

OBJECTIVE

Acellular pertussis vaccine is safe and effective in adults. An explicit recommendation for pertussis booster vaccination in pediatric health care workers is based on the importance of health care workers as a potential source of infection for patients. However, limited information is available on the economic attractiveness of this intervention. We sought to evaluate the health-economic attractiveness of a diphtheria-tetanus-acellular pertussis booster vaccination program for health care workers in a pediatric intensive care setting.

METHODS

We developed a Markov model to calculate the cost-effectiveness of vaccinating NICU health care workers in different proportions ranging from the current strategy of no pertussis booster vaccination program to a vaccination program that achieves between 25% and 95% vaccine coverage.

RESULTS

Implementation of a vaccination program that achieves 25% coverage was projected to be cost-saving compared with no vaccine program. At all coverage levels the intervention reduced costs, increased life expectancy, and was cost-effective. Projections were most sensitive to the risk of a pertussis introduction via an infected health care worker. Once the monthly risk of an introduction exceeded ∼0.3%, implementation of an immunization program with at least 25% coverage provided both greater health and greater economic benefits than having no vaccine program.

CONCLUSIONS

The implementation of a hospital-based and funded diphtheria-tetanus-acellular pertussis vaccine program administered through an occupational health program is cost-effective or cost-saving in the context of pediatric health care facilities in which many of the patients are at risk of serious morbidity and mortality should they acquire pertussis while hospitalized.

Comparative evaluation of the potential impact of rotavirus versus HPV vaccination in GAVI-eligible countries: a preliminary analysis focused on the relative disease burden

BACKGROUND

Immunization policymakers at global and local levels need to establish priorities among new vaccines competing for limited resources. However, comparison of the potential impact of single vaccination programs is challenging, primarily due to the limited number of vaccine analyses as well as their differing analytic approaches and reporting formats. The purpose of this study is to provide early insight into how the comparative impact of different new vaccines could be assessed in resource-poor settings with respect to affordability, cost-effectiveness, and distributional equity.

METHODS

We compared the health, economic, and financial consequences of introducing the two vaccines in 72 GAVI-eligible countries using a number of different outcome measures to evaluate affordability, cost-effectiveness, and distributional equity. We use simple static models to standardize the analytic framework and improve comparability between the two new vaccines. These simple models were validated by leveraging previously developed, more complex models for rotavirus and human papillomavirus (HPV).

RESULTS

With 70% coverage of a single-age cohort of infants and pre-adolescent girls, the lives saved with rotavirus (~274,000) and HPV vaccines (~286,000) are similar, although the timing of averted mortality differs; rotavirus-attributable deaths occur in close proximity to infection, while HPV-related cancer deaths occur largely after age 30. Deaths averted per 1000 vaccinated are 5.2 (rotavirus) and 12.6 (HPV). Disability-adjusted life years (DALYs) averted were ~7.15 million (rotavirus) and ~1.30 million (HPV), reflecting the greater influence of discounting on the latter, given the lagtime between vaccination and averted cancer. In most countries (68 for rotavirus and 66 for HPV, at the cost of I$25 per vaccinated individual) the incremental cost per DALY averted was lower than each country's GDP per capita. Financial resources required for vaccination with rotavirus are higher than with HPV since both genders are vaccinated.

CONCLUSIONS

While lifesaving benefits of rotavirus and HPV vaccines will be realized at different times, the number of lives saved over each target populations' lifetimes will be similar. Model-based analyses that use a standardized analytic approach and generate comparable outputs can enrich the priority-setting dialogue. Although new vaccines may be deemed cost-effective, other factors including affordability and distributional equity need to be considered in different settings. We caution that for priority setting in an individual country, more rigorous comparisons should be performed, using more comprehensive models and considering all relevant vaccines and delivery strategies.

Cost-effectiveness of rotavirus vaccination in the Netherlands; the results of a consensus model

BACKGROUND

Each year rotavirus gastroenteritis results in thousands of paediatric hospitalisations and primary care visits in the Netherlands. While two vaccines against rotavirus are registered, routine immunisation of infants has not yet been implemented. Existing cost-effectiveness studies showed inconsistent results for these vaccines because of lack of consensus on the impact. We aimed to investigate which factors had a major impact on cost-effectiveness and were primarily responsible for the large differences in previously estimated cost-effectiveness ratios.

METHODS

Based on updated data on health outcomes and cost estimates, we re-assessed the cost-effectiveness of routine paediatric rotavirus vaccination within the National Immunization Program for the Netherlands. Two consensus meetings were organised with national and international experts in the field to achieve consensus and resolve potential controversies.

RESULTS

It was estimated that rotavirus vaccination in the Netherlands could avert 34,214 cases of rotavirus gastroenteritis in children aged less than 5 years. Notably, 2,779 hospitalisations were averted of which 315 were extensions of existing hospital stays due to nosocomial rotavirus infection. With a threshold varying from 20K € - 50K € per QALY and according to the base-case scenario, the full vaccination costs per child leading to cost-effectiveness was € 57.76 -€ 77.71. Results were sensitive to the inclusion of potential vaccine induced herd protection, QALY losses and number of deaths associated with rotavirus gastroenteritis.

CONCLUSIONS

Our economic analysis indicates that inclusion of rotavirus vaccination in the Dutch National Immunization Program might be cost-effective depending on the cost of the vaccine and the impact of rotavirus gastroenteritis on children's quality of life.

Modelling the epidemiology of infectious diseases for decision analysis: a primer

The number of economic evaluations related to infectious disease topics has increased over the last 2 decades. However, many such evaluations rely on models that do not take into account unique features of infectious diseases that can affect the estimated value of interventions against them. These include their transmissibility from infected to susceptible individuals, the possibility of acquiring natural immunity following recovery from infection and the uncertainties that arise as a result of their complex natural history and epidemiology. Modellers conducting economic evaluations of infectious disease interventions need to know the main features of different types of infectious disease models, the situations in which they should be applied and the effects of model choices on the cost effectiveness of interventions.