Economic evaluations of childhood influenza vaccination: a critical review

Influenza vaccination in Western Australian children: Exploring the health benefits and cost savings of increased vaccine coverage in children

Introduction

To assess potential benefits and direct healthcare cost savings with expansion of an existing childhood influenza immunisation program, we developed a dynamic transmission model for the state of Western Australia, evaluating increasing coverage in children < 5 years and routinely immunising school-aged children.

Methods

A deterministic compartmental Susceptible-Exposed-Infectious-Recovered age-stratified transmission model was developed and calibrated using laboratory-notification and hospitalisation data. Base case vaccine coverage estimates were derived from 2019 data and tested under moderate, low and high vaccine effectiveness settings. The impact of increased coverage on the burden of influenza, influenza-associated presentations and net costs were assessed using the transmission model and estimated health utilisation costs.

Results

Under base case vaccine coverage and moderate vaccine effectiveness settings, 225,460 influenza cases are expected annually across all ages. Direct healthcare costs of influenza were estimated to be A$27,608,286 per annum, dominated by hospital costs. Net cost savings of >$A1.5 million dollars were observed for every 10 % increase in vaccine coverage in children < 5 years. Additional benefits were observed by including primary school age children (5-11 years) in the funded influenza vaccination program - a reduction in cases, presentations, hospitalisations and approximately $A4 million net costs savings were observed for every 10 % increase in coverage. The further addition of older children (12-17 years) resulted in only moderate additional net cost savings figures, compared with a 5-11year-old program alone. Net costs savings were predominantly derived by a reduction in influenza-associated hospitalisation in adults.

Conclusions

Any increase in influenza vaccine coverage in children < 5 years, above a base case of 50 % coverage resulted in a substantive reduction in influenza cases, presentations, hospitalisations and net costs when applied to the West Australian population. However, the most impactful pediatric program, from both a disease prevention and costs perspective, would be one that increased vaccination coverage among primary-school aged children.

Canadian Association of Gastroenterology Clinical Practice Guideline for Immunizations in Patients With Inflammatory Bowel Disease (IBD)-Part 2: Inactivated Vaccines

BACKGROUND AND AIMS

The effectiveness and safety of vaccinations can be altered by immunosuppressive therapies, and perhaps by inflammatory bowel disease (IBD) itself. These recommendations developed by the Canadian Association of Gastroenterology and endorsed by the American Gastroenterological Association, aim to provide guidance on immunizations in adult and pediatric patients with IBD. This publication focused on inactivated vaccines.

METHODS

Systematic reviews evaluating the efficacy, effectiveness, and safety of vaccines in patients with IBD, other immune-mediated inflammatory diseases, and the general population were performed. Critical outcomes included mortality, vaccine-preventable diseases, and serious adverse events. Immunogenicity was considered a surrogate outcome for vaccine efficacy. Certainty of evidence and strength of recommendations were rated according to the GRADE (Grading of Recommendation Assessment, Development, and Evaluation) approach. Key questions were developed through an iterative online platform, and voted on by a multidisciplinary group. Recommendations were formulated using the Evidence-to-Decision framework. Strong recommendation means that most patients should receive the recommended course of action, whereas a conditional recommendation means that different choices will be appropriate for different patients.

RESULTS

Consensus was reached on 15 of 20 questions. Recommendations address the following vaccines: Haemophilus influenzae type b, recombinant zoster, hepatitis B, influenza, pneumococcus, meningococcus, tetanus-diphtheria-pertussis, and human papillomavirus. Most of the recommendations for patients with IBD are congruent with the current Centers for Disease Control and Prevention and Canada's National Advisory Committee on Immunization recommendations for the general population, with the following exceptions. In patients with IBD, the panel suggested Haemophilus influenzae type b vaccine for patients older than 5 years of age, recombinant zoster vaccine for adults younger than 50 year of age, and hepatitis B vaccine for adults without a risk factor. Consensus was not reached, and recommendations were not made for 5 statements, due largely to lack of evidence, including double-dose hepatitis B vaccine, timing of influenza immunization in patients on biologics, pneumococcal and meningococcal vaccines in adult patients without risk factors, and human papillomavirus vaccine in patients aged 27-45 years.

CONCLUSIONS

Patients with IBD may be at increased risk of some vaccine-preventable diseases. Therefore, maintaining appropriate vaccination status in these patients is critical to optimize patient outcomes. In general, IBD is not a contraindication to the use of inactivated vaccines, but immunosuppressive therapy may reduce vaccine responses.

Canadian Association of Gastroenterology Clinical Practice Guideline for Immunizations in Patients With Inflammatory Bowel Disease (IBD)-Part 2: Inactivated Vaccines

BACKGROUND AND AIMS

The effectiveness and safety of vaccinations can be altered by immunosuppressive therapies, and perhaps by inflammatory bowel disease (IBD) itself. These recommendations developed by the Canadian Association of Gastroenterology and endorsed by the American Gastroenterological Association, aim to provide guidance on immunizations in adult and pediatric patients with IBD. This publication focused on inactivated vaccines.

METHODS

Systematic reviews evaluating the efficacy, effectiveness, and safety of vaccines in patients with IBD, other immune-mediated inflammatory diseases, and the general population were performed. Critical outcomes included mortality, vaccine-preventable diseases, and serious adverse events. Immunogenicity was considered a surrogate outcome for vaccine efficacy. Certainty of evidence and strength of recommendations were rated according to the GRADE (Grading of Recommendation Assessment, Development, and Evaluation) approach. Key questions were developed through an iterative online platform, and voted on by a multidisciplinary group. Recommendations were formulated using the Evidence-to-Decision framework. Strong recommendation means that most patients should receive the recommended course of action, whereas a conditional recommendation means that different choices will be appropriate for different patients.

RESULTS

Consensus was reached on 15 of 20 questions. Recommendations address the following vaccines: Haemophilus influenzae type b, recombinant zoster, hepatitis B, influenza, pneumococcus, meningococcus, tetanus-diphtheria-pertussis, and human papillomavirus. Most of the recommendations for patients with IBD are congruent with the current Centers for Disease Control and Prevention and Canada's National Advisory Committee on Immunization recommendations for the general population, with the following exceptions. In patients with IBD, the panel suggested Haemophilus influenzae type b vaccine for patients older than 5 years of age, recombinant zoster vaccine for adults younger than 50 year of age, and hepatitis B vaccine for adults without a risk factor. Consensus was not reached, and recommendations were not made for 5 statements, due largely to lack of evidence, including double-dose hepatitis B vaccine, timing of influenza immunization in patients on biologics, pneumococcal and meningococcal vaccines in adult patients without risk factors, and human papillomavirus vaccine in patients aged 27-45 years.

CONCLUSIONS

Patients with IBD may be at increased risk of some vaccine-preventable diseases. Therefore, maintaining appropriate vaccination status in these patients is critical to optimize patient outcomes. In general, IBD is not a contraindication to the use of inactivated vaccines, but immunosuppressive therapy may reduce vaccine responses.

Cost-effectiveness of childhood influenza vaccination in Europe: results from a systematic review

Introduction: Influenza can be a significant public health problem. Nevertheless, it is preventable through vaccination. Concerning the pediatric population, the recommendation of influenza vaccination is under-represented in many European countries. The aim of this systematic review is to evaluate the cost-effectiveness of universal childhood vaccination against influenza in Europe.Areas covered: We conducted a systematic review of original article assessing the cost-effectiveness of influenza vaccination by searching PubMed, Embase and Scopus databases for studies in English, starting from January 1^st, 2010 up to October 21^st, 2020.Expert opinion: Our literature review showed that all studies identified highlight that pediatric vaccinations using a live vaccine, especially in the quadrivalent formulation, are cost-effective compared to current vaccinations (elderly and at-risk groups) with TIV or no vaccination. A significant contribution to this positive economic profile is due to the indirect protection. Already many clinical data report the relevant direct and indirect impact of vaccination against influenza for younger subjects. The recent studies collected in this review showed also that the pediatric vaccination is also cost-effective. Therefore, decision-makers should now consider this new favorable evidence.

Inclusion of Safety-Related Issues in Economic Evaluations for Seasonal Influenza Vaccines: A Systematic Review

(1) Background: Vaccines for seasonal influenza are a good preventive and cost-effective strategy. However, it is unknown if and how these economic evaluations include the adverse events following immunization (AEFI), and what the impact of such inclusion is on the health economic outcomes. (2) Methods: We searched the literature, up to January 2020, to identify economic evaluations of seasonal influenza vaccines that considered AEFIs. The review protocol was published in PROSPERO (CDR42017058523). (3) Results: A total of 52 economic evaluations considered AEFI-related parameters in their analyses, reflecting 16% of the economic evaluations on seasonal influenza vaccines in the initial study selection. Most studies used the societal perspective (64%) and evaluated vaccination of children (37%). Where considered, studies included direct medical costs of AEFIs (90%), indirect costs (27%), and disutilities/quality-adjusted life years loss due to AEFIs (37%). The majority of these studies accounted for the effects of the costs of AEFI on cost-effectiveness for Guillain–Barré syndrome. In those papers allowing cost share estimation, direct medical cost of AFEIs was less than 2% of total direct costs. (4) Conclusions: Although the overall impact of AEFIs on the cost-effectiveness outcomes was found to be low, we urge their inclusion in economic evaluations of seasonal influenza vaccines to reflect comprehensive reports for the decision makers and end-users of the vaccination strategies.

Influenza vaccination in the COVID-19 era

Influenza spreads globally annually with significant paediatric and adult attack rates and considerable morbidity, mortality and the exacerbation of extant chronic disease. In the northern and southern hemispheres, outbreaks occur mainly in the respective winter seasons. Influenza vaccination is available but only partially effective. In the absence of a vaccine, in winter, novel coronavirus COVID-19 will also circulate in parallel with seasonal influenza. Thus far it appears that with the current strains of these two viruses, the clinical outcome of co-infection is not significantly worse than infection with COVID-19 alone. However, several strains of influenza circulate, including strains still to come. Similarly, COVID-19 has several strains, with probably more to come. This paper discusses these issues and estimates ideal minimum influenza vaccination coverage based on an estimated influenza Basic Reproduction Number (R0) of 0.9-2.1 so as to obtain herd immunity or approach it. There is a strong argument for attempting near universal population coverage with the annual influenza vaccine leading up to next winter.

Model Comparisons of the Effectiveness and Cost-Effectiveness of Vaccination: A Systematic Review of the Literature

OBJECTIVES

To describe all published articles that have conducted comparisons of model-based effectiveness and cost-effectiveness results in the field of vaccination. Specific objectives were to 1) describe the methodologies used and 2) identify the strengths and limitations of the studies.

METHODS

We systematically searched MEDLINE and Embase databases for studies that compared predictions of effectiveness and cost-effectiveness of vaccination of two or more mathematical models. We categorized studies into two groups on the basis of their data source for comparison (previously published results or new simulation results) and performed a qualitative synthesis of study conclusions.

RESULTS

We identified 115 eligible articles (only 5% generated new simulations from the reviewed models) examining the effectiveness and cost-effectiveness of vaccination against 14 pathogens (69% of studies examined human papillomavirus, influenza, and/or pneumococcal vaccines). The goal of most of studies was to summarize evidence for vaccination policy decisions, and cost-effectiveness was the most frequent outcome examined. Only 33%, 25%, and 3% of studies followed a systematic approach to identify eligible studies, assessed the quality of studies, and performed a quantitative synthesis of results, respectively. A greater proportion of model comparisons using published studies followed a systematic approach to identify eligible studies and to assess their quality, whereas more studies using new simulations performed quantitative synthesis of results and identified drivers of model conclusions. Most comparative modeling studies concluded that vaccination was cost-effective.

CONCLUSIONS

Given the variability in methods used to conduct/report comparative modeling studies, guidelines are required to enhance their quality and transparency and to provide better tools for decision making.

The impact of influenza infection on young children, their family and the health care system

Background

Influenza is a major cause of respiratory illness in young children. Assessing the impact of infection on children and the community is required to guide immunisation policies.

Objectives

To describe the impact of laboratory‐proven influenza in young children and to compare its impact with that of other respiratory viruses on the child, their family and the health care system.

Methods

Preschool children presenting for care or admission to a tertiary paediatric hospital during the 2008‐2014 influenza seasons were tested for respiratory virus by polymerase chain reaction and culture. Parental surveys were used to determine the impact of infection on illness duration, medication use, absenteeism and health service utilisation. Multivariate regression analyses were used to assess the impact of influenza and to evaluate the association between influenza status and outcomes.

Results

Among 1191 children assessed, 238 had influenza. Among children with influenza, 87.8% were administered antipyretics and 40.9% antibiotics. 28.6% had secondary complications. 65.4% of children missed school/day care, and 53.4% of parents missed work. When influenza and other viruses were compared, significant differences were noted including duration of illness (influenza: 9.54 days, other viruses: 8.50 days; P = 0.005) and duration of absenteeism for both the child (23.1 vs 17.3 hours; P = 0.015) and their parents (28.5 vs 22.7 hours; P = 0.012).

Conclusions

Influenza infection in young children has a significant impact on medication use, absenteeism and the use of health care service. Significant differences are identified when compared with other ILI. These data demonstrate that influenza prevention strategies including immunisation are likely to have wide and significant impacts.

WHO guide on the economic evaluation of influenza vaccination

Influenza is responsible for substantial morbidity and mortality across the globe, with a large share of the total disease burden occurring in low- and middle-income countries (LMICs). There have been relatively few economic evaluations assessing the value of seasonal influenza vaccination in LMICs. The purpose of this guide is to outline the key theoretical concepts and best practice in methodologies and to provide guidance on the economic evaluation of influenza vaccination in LMICs. It outlines many of the influenza vaccine-specific challenges and should help to provide a framework for future evaluations in the area to build upon.

Influenza vaccination in preventing outbreaks in schools: A long-term ecological overview

Influenza vaccination is the most effective way to reduce the incidence of influenza infections. However, the role of influenza vaccination, such as school-based influenza vaccination, in preventing the influenza outbreaks in schools remains unclear now. In this study, a total of 286 school febrile outbreaks involving 6863 cases in the Beijing area from September 1, 2006 to March 31, 2017 were analyzed. We also tested 294 circulating strains isolated in Beijing during the same period and compared with that of vaccine strains identified every influenza season. The virological match/mismatch between vaccine strains and circulating strains, and the coverage of vaccination in schools were analyzed against outbreaks during the 11 years. It showed that over 80% school febrile outbreaks were caused by influenza A/B virus, the most frequent being A(H3N2) virus (53.25%), followed by A(H1N1)pdm09 virus (25.11%) and B virus (21.64%). More importantly, low vaccine coverage (in 2006-2007 influenza season) and vaccine mismatch (in 2014-2015 and 2015-2016 influenza season) were associated with an increased number of influenza school outbreaks. High vaccination coverage with a matched vaccine can significantly reduce influenza outbreaks in schools (OR: 0.111, p < .001). We have shown the effectiveness of school-based influenza vaccination in preventing outbreaks using trivalent inactivated influenza vaccine in schools. Thus the school-based vaccine policy should be paid more attention in China and other countries worldwide.

Systematic review of the cost-effectiveness of influenza immunization programs

BACKGROUND

Seasonal influenza immunization programs vary widely across jurisdictions. In Canada, some provinces offer universal programs while others target specific population groups. However, whether targeted or universal programs provide more benefit and value-for-money is unclear. The cost-effectiveness of influenza immunization programs was systematically reviewed to inform policy.

METHODS

Citation databases and the grey literature were searched for economic evaluations of influenza immunization programs. Eligible studies were appraised using the Scottish Intercollegiate Guidelines Network (SIGN) checklist with supplemental WHO vaccine-related questions. Data from high quality studies was extracted and the studies reviewed.

RESULTS

A total of 41influenza immunization studies were identified. Of these, 31 were high quality. For pregnant and postpartum women, vaccinating all versus only high risk women study results ranged from dominance (less costly and more effective) to $9773 per QALY gained (societal) and from dominance to $58,000 per QALY gained (healthcare system). Studies of vaccinating all versus only high risk children found vaccination to be dominant to $47,000 per QALY gained (societal), and dominant to $18,000 per QALY gained (healthcare system). Vaccinating high risk adults was highly cost-effective and vaccinating health care workers resulted in $35,000 per QALY gained. Results for healthy working adults were mixed and sensitive to vaccine uptake, efficacy, and productivity loss.

CONCLUSIONS

From the societal perspective, vaccination was cost-effective for children, pregnant and postpartum women, high risk groups, and in some cases, healthy working age adults. Immunization programs using group administration are more cost-effective than programs using individual administration. The perspective, programmatic design, setting, and inclusion of herd immunity affects cost-effectiveness. In regions with targeted programs, re-evaluating "high risk" criteria and consideration of a universal program is warranted.

Economic Evaluation of Vaccination Programmes in Older Adults and the Elderly: Important Issues and Challenges

High-income countries are undergoing demographic transitions towards populations with substantial larger proportions of older adults. Due to the increased susceptibility of older adults to infectious diseases and their consequences, vaccination programmes are an important health intervention to help maintain healthy ageing. While much of the existing literature suggests that current vaccination programmes targeted at older adults and the elderly are likely to be cost effective in high-income countries, we argue that it is important to more fully consider some important issues and challenges. Since the majority of vaccines have been developed for children, economic evaluations of vaccination programmes have consequentially tended to focus on this age group and on how to incorporate herd-immunity effects. While programmes targeted at older adults and the elderly may also induce some herd effects, there are other important challenges to consider in these economic evaluations. For example, age and time effects in relation to vaccine efficacy and duration of immunity, as well as heterogeneity between targeted individuals in terms of risk of infection, severity of disease and response to vaccination. For some pathogens, there is also the potential for interactions with childhood programmes in the form of herd-immunity effects.

Targeted vaccination in healthy school children - Can primary school vaccination alone control influenza?

BACKGROUND

The UK commenced an extension to the seasonal influenza vaccination policy in autumn 2014 that will eventually see all healthy children between the ages of 2-16 years offered annual influenza vaccination. Models suggest that the new policy will be both highly effective at reducing the burden of influenza as well as cost-effective. We explore whether targeting vaccination at either primary or secondary schools would be more effective and/or cost-effective than the current strategy.

METHODS

An age-structured deterministic transmission dynamic SEIR-type mathematical model was used to simulate a national influenza outbreak in England. Costs including GP consultations, hospitalisations due to influenza and vaccinations were compared to potential gains in quality-adjusted life years achieved through vaccinating healthy children. Costs and benefits of the new JCVI vaccination policy were estimated over a single season, and compared to the hypothesised new policies of targeted and heterogeneous vaccination.

FINDINGS AND CONCLUSION

All potential vaccination policies were highly cost-effective. Influenza transmission can be eliminated for a particular season by vaccinating both primary and secondary school children, but not by vaccinating only one group. The most cost-effective policy overall is heterogeneous vaccination coverage with 48% uptake in primary schools and 34% in secondary schools. The Joint Committee on Vaccination and Immunisation can consider a modification to their policy of offering seasonal influenza vaccinations to all healthy children of ages 2-16 years.

Understanding the cost-effectiveness of influenza vaccination in children: methodological choices and seasonal variability

BACKGROUND

The universal vaccination of children for influenza has recently been recommended in the UK and is being considered in other developed countries.

OBJECTIVES

The aim of this study was to explore the potential costs and benefits of childhood influenza vaccination to gain a better understanding of the key drivers of cost-effectiveness.

METHODS

As our case study we examined the cost-effectiveness of vaccination in Australian schoolchildren using an age-stratified Susceptible Exposed Infectious Recovered model.

RESULTS

The results of this study highlight the critical role that methodological choices play in determining the cost-effectiveness of influenza vaccination. These choices include decisions about the structure of the model (including/excluding herd immunity) and what costs and benefits to include in the analysis. In scenarios where herd protection was included we estimated that the program was likely to be cost-effective. The study also illustrates the importance of the inherent seasonal variability of influenza, which can produce counter-intuitive results, with low transmission seasons being easier to control by vaccination but resulting in fewer benefits.

CONCLUSIONS

Universal childhood influenza vaccination is likely to be cost-effective if a substantial herd protection effect can be achieved by the program. However, it is important that decision makers understand the role of seasonal variability and the impact of alternative methodological choices in economic evaluations of influenza vaccination.

Key issues for estimating the impact and cost-effectiveness of seasonal influenza vaccination strategies

Many countries have considered or are considering modifying their seasonal influenza immunization policies. Estimating the impact of such changes requires understanding the existing clinical and economic burden of influenza, as well as the potential impact of different vaccination options. Previous studies suggest that vaccinating clinical risk groups, health care workers, children and the elderly may be cost-effective. However, challenges in such estimation include: (1) potential cases are not usually virologically tested; (2) cases have non-specific symptoms and are rarely reported to surveillance systems; (3) endpoints for influenza proxies (such as influenza-like illness) need to be matched to case definitions for treatment costs, (4) disease burden estimates vary from year to year with strain transmissibility, virulence and prior immunity, (5) methods to estimate productivity losses due to influenza vary, (6) vaccine efficacy estimates from trials differ due to variation in subtype prevalence, vaccine match and case ascertainment, and (7) indirect (herd) protection from vaccination depends on setting-specific variables that are difficult to directly measure. Given the importance of knowing the impact of changes to influenza policy, such complexities need careful treatment using tools such as population-based trial designs, meta-analyses, time-series analyses and transmission dynamic models.

Economic benefits of inactivated influenza vaccines in the prevention of seasonal influenza in children

The aim of this study was to systematically review published studies that evaluated the efficiency of inactivated influenza vaccination in preventing seasonal influenza in children. The vaccine evaluated was the influenza-inactivated vaccine in 10 studies and the virosomal inactivated vaccine in 3 studies. The results show that yearly vaccination of children with the inactivated influenza vaccine saves money from the societal and family perspectives but not from the public or private provider perspective. When vaccination does not save money, the cost-effectiveness ratios were very acceptable. It can be concluded, that inactivated influenza vaccination of children is a very efficient intervention.