Public health impact and economic benefits of quadrivalent influenza vaccine in Latin America

Comparisons in the Health and Economic Assessments of Using Quadrivalent Versus Trivalent Influenza Vaccines: A Systematic Literature Review

OBJECTIVES

Seasonal influenza vaccines protect against 3 (trivalent influenza vaccine [IIV3]) or 4 (quadrivalent influenza vaccine [IIV4]) viruses. IIV4 costs more than IIV3, and there is a trade-off between incremental cost and protection. This is especially the case in low- and middle-income countries (LMICs) with limited budgets; previous reviews have not identified studies of IIV4-IIV3 comparisons in LMICs. We summarized the literature that compared health and economic outcomes of IIV4 and IIV3, focused on LMICs.

METHODS

We systematically searched 5 databases for articles published before October 6, 2021, that modeled health or economic effects of IIV4 versus IIV3. We abstracted data and compared findings among countries and models.

RESULTS

Thirty-eight studies fit our selection criteria; 10 included LMICs. Most studies (N = 31) reported that IIV4 was cost-saving or cost-effective compared with IIV3; we observed no difference in health or economic outcomes between LMICs and other countries. Based on cost differences of influenza vaccines, only one study compared coverage of IIV3 with IIV4 and reported that the maximum IIV4 price that would still yield greater public health impact than IIV3 was 13% to 22% higher than IIV3.

CONCLUSIONS

When vaccination coverage with IIV4 and IIV3 is the same, IIV4 tends to be not only more effective but more cost-effective than IIV3, even with relatively high price differences between vaccine types. Alternatively, where funding is limited as in most LMICs, higher vaccine coverage can be achieved with IIV3 than IIV4, which could result in more favorable health and economic outcomes.

A randomized, double-blind, non-inferiority trial comparing the immunogenicity and safety of two seasonal inactivated influenza vaccines in adults

BACKGROUND

To enhance the production and availability of influenza vaccines in different regions of the world is paramount to mitigate the global burden of this disease. Instituto Butantan developed and manufactured an embryonated egg-based inactivated split-virion trivalent seasonal influenza vaccine as part of a technology transfer partnership with Sanofi Pasteur.

METHODS

This is a phase IV, randomized, double-blind, active-controlled, multicenter clinical trial including adults 18-60 and > 60 years recruited during the 2019 southern hemisphere influenza season. Subjects were randomized 1:1 to receive either the Sanofi Pasteur Trivalent Seasonal Influenza Vaccine (SP-TIV) or Instituto Butantan Trivalent Seasonal Influenza Vaccine (IB-TIV). Hemagglutinin inhibition antibody titers were assessed pre-vaccination and 21 days post-vaccination.

RESULTS

624 participants were randomized and vaccinated. In both intention-to-treat and per-protocol analysis, non-inferiority of the SP-TIV versus IB-TIV was demonstrated for the three influenza strains. In the per-protocol analysis, the SP-GMT/IB-GMT ratios for H1N1, H3N2, and B were 0.9 (95%CI, 0.7-1.1), 1.2 (95%CI, 1.0-1.4), and 1.1 (95%CI, 0.9-1.3), respectively. Across vaccination groups, the most common adverse reactions (AR) were limited to the injection-site, including pain and tenderness. The majority of the ARs were graded 1 and/or 2 and lasted less than one day. No serious adverse reaction was observed.

CONCLUSION

This study demonstrated the non-inferiority of the immunogenicity of a single-dose of Instituto Butantan versus a single dose of the Sanofi Pasteur Seasonal Trivalent Influenza Vaccine in adults. Both vaccines were well tolerated and presented similar safety profiles.

Switching from trivalent to quadrivalent inactivated influenza vaccines in Uruguay: a cost-effectiveness analysis

We evaluated the cost-utility of replacing trivalent influenza vaccine (TIV) with quadrivalent influenza vaccine (QIV) in the current target populations in Uruguay. An existing decision-analytic static cost-effectiveness model was adapted for Uruguay. The population was stratified into age groups. Costs and outcomes were estimated for an average influenza season, based on observed rates from 2013 to 2019 inclusive. Introducing QIV instead of TIV in Uruguay would avoid around 740 additional influenza cases, 500 GP consultations, 15 hospitalizations, and three deaths, and save around 300 workdays, for the same vaccination coverage during an average influenza season. Most of the influenza-related consultations and hospitalizations would be avoided among children ≤4 and adults ≥65 years of age. Using QIV rather than TIV would cost an additional ~US$729,000, but this would be partially offset by savings in consultations and hospitalization costs. The incremental cost per quality-adjusted life-year (QALY) gained with QIV would be in the order of US$18,000 for both the payor and societal perspectives, for all age groups, and around US$12,000 for adults ≥65 years of age. The main drivers influencing the incremental cost-effectiveness ratio were the vaccine efficacy against the B strains and the percentage of match each season with the B strain included in TIV. Probabilistic sensitivity analysis showed that switching to QIV would provide a favorable cost-utility ratio for 50% of simulations at a willingness-to-pay per QALY of US$20,000. A switch to QIV is expected to be cost-effective for the current target populations in Uruguay, particularly for older adults.

Cost-effectiveness of seasonal influenza vaccination in pregnant women, healthcare workers and adults >= 60 years of age in Lao People's Democratic Republic

BACKGROUND

Pregnant women, healthcare workers (HW), and adults >= 60 years have shown an increased vulnerability to seasonal influenza virus infections and/or complications. In 2012, the Lao People's Democratic Republic (Lao PDR) initiated a national influenza vaccination program for these target groups. A cost-effectiveness evaluation of this program was undertaken to inform program sustainability.

METHODS

We designed a decision-analytical model and collected influenza-related medical resource utilization and cost data, including indirect costs. Model inputs were obtained from medical record abstraction, interviews of patients and staff at hospitals in the national influenza sentinel surveillance system and/or from literature reviews. We compared the annual disease and economic impact of influenza illnesses in each of the target groups in Lao PDR under scenarios of no vaccination and vaccination, and then estimated the cost-effectiveness of the vaccination program. We performed sensitivity analyses to identify influential variables.

RESULTS

Overall, the vaccination of pregnant women, HWs, and adults >= 60 years could annually save 11,474 doctor visits, 1,961 days of hospitalizations, 43,027 days of work, and 1,416 life-years due to laboratory-confirmed influenza illness. After comparing the total vaccination program costs of 23.4 billion Kip, to the 18.4 billion Kip saved through vaccination, we estimated the vaccination program to incur a net cost of five billion Kip (599,391 USD) annually. The incremental cost per life-year saved (ICER) was 44 million Kip (5,295 USD) and 6.9 million Kip (825 USD) for pregnant women and adults >= 60 years, respectively. However, vaccinating HWs provided societal cost-savings, returning 2.88 Kip for every single Kip invested. Influenza vaccine effectiveness, attack rate and illness duration were the most influential variables to the model.

CONCLUSION

Providing influenza vaccination to HWs in Lao PDR is cost-saving while vaccinating pregnant women and adults >= 60 is cost-effective and highly cost-effective, respectively, per WHO standards.

Inclusion of Additional Unintended Consequences in Economic Evaluation: A Systematic Review of Immunization and Tuberculosis Cost-Effectiveness Analyses

OBJECTIVE

Our objective was to review economic evaluations of immunization and tuberculosis to determine the extent to which additional unintended consequences were taken into account in the analysis and to describe the methodological approaches used to estimate these, where possible.

METHODS

We sourced the vaccine economic evaluations from a previous systematic review by Nymark et al. (2009-2015) and searched PubMed/MEDLINE and Embase from 2015 to 2019 using the same search strategy. For tuberculosis economic evaluations, we extracted studies from 2009 to 2019 that were published in a previous review by Siapka et al. We followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidance. Studies were classified according to the categories and subcategories (e.g., herd immunity, non-specific effects, and labor productivity) defined in a framework identifying additional unintended consequences by Nymark and Vassall. Where possible, methods for estimating the additional unintended consequences categories and subcategories were described. We evaluated the reporting quality of included studies according to the Consolidated Health Economic Evaluation Reporting Standards (CHEERS) extraction guideline.

RESULTS

We identified 177 vaccine cost-effectiveness analyses (CEAs) between 2009 and 2019 that met the inclusion criteria. Of these, 98 included unintended consequences. Of the total 98 CEAs, overall health consequence categories were included 73 times; biological categories: herd immunity 43 times; pathogen response: resistance 15 times; and cross-protection 15 times. For health consequences pertaining to the supply-side (health systems) categories, side effects were included five times. On the nonhealth demand side (intrahousehold), labor productivity was included 60 times. We identified 29 tuberculosis CEAs from 2009 to 2019 that met the inclusion criteria. Of these, six articles included labor productivity, four included indirect transmission effects, and one included resistance. Between 2009 and 2019, only 34% of tuberculosis CEAs included additional unintended consequences, compared with 55% of vaccine CEAs.

CONCLUSIONS

The inclusion of additional unintended consequences in economic evaluations of immunization and tuberculosis continues to be limited. Additional unintended consequences of economic benefits, such as those examined in this review and especially those that occur outside the health system, offer valuable information to analysts. Further work on appropriate ways to value these additional unintended consequences is still warranted.

Burden of Seasonal Influenza A and B in Panama from 2011 to 2017: An Observational Retrospective Database Study

Introduction

Influenza A and B viruses constantly evolve and cause seasonal epidemics and sporadic outbreaks. Therefore, epidemiological surveillance is critical for monitoring their circulation pattern. Trivalent and quadrivalent vaccine formulations are available in Panama (until and since 2016, respectively). Herein, we analysed influenza A and B epidemiological patterns in Panama.

Methods

This was a retrospective descriptive analysis of all laboratory-confirmed influenza nasopharyngeal samples recorded between 2011 and 2017 in the nationwide surveillance database of Gorgas Memorial Institute for Health Studies. The analysis involved data relative to demographic information, virus type, subtype and lineage, geographic region, treatment and outcomes. The percentage level of mismatch between circulating and vaccine-recommended B lineage was assessed for each May–October influenza season.

Results

Among 1839 influenza cases, 79.6% were type A and 20.4% were type B. Most of them were observed in Panama City (54.7%) followed by the West (23.2%) and Central (16.7%) regions; across all regions, influenza A and B cases were distributed in a 4:1 ratio. Overall, approximately half were hospitalized (52.0% for type A; 45.5% for type B) and 11 (0.6%) died. Treatment, usually antimicrobial, was administered in 15.1% of cases. Children less than 2 years old were the most affected by this disease. Influenza type A circulated every year, while influenza B only circulated in 2012, 2014 and 2017. In the 2012 May–October influenza B season, the predominant lineage was B/Victoria and a switch to B/Yamagata was observed in 2014. Both lineages co-circulated in 2017, leading to a 38.9% B-lineage-level vaccine mismatch.

Conclusion

Influenza A was predominant among all ages and children less than 2 years and inhabitants of Panama City reported the highest circulation rate. In 2017, co-circulation of both B lineages led to a vaccine mismatch. Continuous monitoring of seasonal influenza is critical to establish immunization recommendations.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40121-021-00501-y.

Influenza or “flu” is caused by influenza viruses A and B and its symptoms range from mild to severe. This virus is constantly evolving; thus, careful monitoring of influenza is important to update immunization and vaccine recommendations yearly. This study used data from surveillance centres in Panama from 2011 to 2017 and evaluated the number of flu cases by age, gender, region, virus type, symptoms, comorbidities, treatment, coinfections with other viruses, and the circulating influenza subtype and the vaccine recommended each year. We found several points: almost 80% of cases were influenza A; most of the positive samples were found in children less than 2 years old and the Panama city region; more than 50% of influenza cases needed hospitalization; and in 2017 a mismatch was detected between the circulating influenza subtype and the recommended vaccine. This study helped to better characterize influenza circulation patterns and the burden of the disease during 2011–2017. We concluded that continuous monitoring of the influenza cases is necessary to establish future vaccination recommendations.

Influenza Vaccination for the Prevention of Cardiovascular Disease in the Americas: Consensus document of the Inter-American Society of Cardiology and the Word Heart Federation

Background

Cardiovascular mortality is decreasing but remains the leading cause of death world-wide. Respiratory infections such as influenza significantly contribute to morbidity and mortality in patients with cardiovascular disease. Despite of proven benefits, influenza vaccination is not fully implemented, especially in Latin America.

Objective

The aim was to develop a regional consensus with recommendations regarding influenza vaccination and cardiovascular disease.

Methods

A multidisciplinary team composed by experts in the management and prevention of cardiovascular disease from the Americas, convened by the Inter-American Society of Cardiology (IASC) and the World Heart Federation (WHF), participated in the process and the formulation of statements. The modified RAND/UCLA methodology was used. This document was supported by a grant from the WHF.

Results

An extensive literature search was divided into seven questions, and a total of 23 conclusions and 29 recommendations were achieved. There was no disagreement among experts in the conclusions or recommendations.

Conclusions

There is a strong correlation between influenza and cardiovascular events. Influenza vaccination is not only safe and a proven strategy to reduce cardiovascular events, but it is also cost saving. We found several barriers for its global implementation and potential strategies to overcome them.

Cost-Effectiveness Analysis of Switching from Trivalent to Quadrivalent Seasonal Influenza Vaccine in Argentina

The burden of seasonal influenza disease in Argentina is considerable. The cost-effectiveness of trivalent (TIV) versus quadrivalent influenza vaccine (QIV) in Argentina was assessed. An age-stratified, static, decision-tree model compared the costs and benefits of vaccination for an average influenza season. Main outcomes included: numbers of influenza cases; general practitioner (GP) visits; complicated ambulatory cases; hospitalizations; deaths averted; and costs per quality-adjusted life years (QALYs) gained. Epidemiological data from Argentina for 2014–2019 were used to determine the proportion of A and B strain cases, and the frequency of mismatch between vaccine and circulating B strains. To manage uncertainty, one-way and probabilistic sensitivity analyses were performed. Switching from TIV to QIV would prevent 19,128 influenza cases, 16,164 GP visits, 2440 complicated ambulatory cases, 524 hospitalizations, and 82 deaths. Incremental cost–effectiveness ratios (ICERs) per QALY were 13,590 and 11,678 USD from the payer’s and societal perspectives, respectively. The greatest health benefits and direct medical cost savings would occur in ≥ 65-year-olds. One-way sensitivity analyses demonstrated the principal drivers of ICER to be vaccine acquisition costs, environmental B strain predominance, and B strain mismatch. Introducing QIV in Argentina would be beneficial and cost-effective relative to TIV, particularly in older adults.

Situational assessment of adult vaccine preventable disease and the potential for immunization advocacy and policy in low- and middle-income countries

By 2050, the number of adults over 65 years of age will be double the under-5 population, and heavily concentrated in low- and middle-income countries. Population growth and increasing life expectancies call for effective healthy aging strategies inclusive of immunization to reduce the burden of vaccine-preventable diseases, improve quality of life, and mitigate antimicrobial resistance. Based on a review of available literature on the pneumococcal disease, influenza, and herpes zoster epidemiology and economic burden, and the health systems and policy barriers for adult immunization, we identified evidence gaps and considerations for prioritizing adult immunization. The body of evidence for adult immunization and the health and economic burden of adult disease is heavily concentrated in high-income countries. The few countries reporting adult immunization policies generally focus on high-risk groups. Despite robust child immunization programs in most countries, adult immunization programs and policies lag far behind and there is a general lack of appropriate delivery platforms. Global adult disease burden and economic costs are substantial but evidence from low- and middle-income countries is limited. There is a need for a strengthened evidence base and political commitment to drive a comprehensive, global technical consensus on adult immunization.

Cost Utility of Switching From Trivalent to Quadrivalent Influenza Vaccine in Turkey

OBJECTIVES

Trivalent influenza vaccines (TIVs) are widely used but protect against only 1 of the 2 co-circulating influenza B virus lineages. Quadrivalent influenza vaccines (QIVs) include a B strain from each lineage to overcome mismatches. The main objective of this study was to determine the cost-utility and budget impact of switching from vaccination with TIV to QIV in the population recommended for influenza vaccination in Turkey.

METHODS

A static cohort cost-effectiveness model was developed to predict influenza-related costs and outcomes under a QIV versus a TIV program during an influenza season. The model was informed by data from Turkey on influenza strain distribution, influenza-attributable outcomes, and associated costs over the seasons 2010/2011 to 2016/2017. The effectiveness of each strategy was measured through quality-adjusted life-years (QALYs), and comparisons were based on the incremental cost-effectiveness ratio.

RESULTS

In an average influenza season, the model showed that switching from TIV to QIV would prevent an additional 15 092 cases of influenza, 6311 general practitioner visits, 94 hospitalizations, 13 deaths, and gain 440 QALYs. From the societal perspective, this amounted to total cost savings of international dollars (I$) 1102 710 (US$388 643). The incremental cost-effectiveness ratio when using QIV over TIV was I$55 248/QALY gained. Switching to QIV is mostly cost-effective among older adults with I$36 413.38/QALY. Sensitivity analysis showed that vaccine effectiveness, B strain mismatch, and influenza visits highly impact the cost-effectiveness results.

CONCLUSION

Switching from TIV to QIV is likely to be cost-effective in Turkey, yet highly dependent on the severity of the influenza season, B strain epidemiology, and vaccine effectiveness.

Impact of quadrivalent influenza vaccines in Brazil: a cost-effectiveness analysis using an influenza transmission model

BACKGROUND

Influenza epidemics significantly weight on the Brazilian healthcare system and its society. Public health authorities have progressively expanded recommendations for vaccination against influenza, particularly to the pediatric population. However, the potential mismatch between the trivalent influenza vaccine (TIV) strains and those circulating during the season remains an issue. Quadrivalent vaccines improves vaccines effectiveness by preventing any potential mismatch on influenza B lineages.

METHODS

We evaluate the public health and economic benefits of the switch from TIV to QIV for the pediatric influenza recommendation (6mo-5yo) by using a dynamic epidemiological model able to consider the indirect impact of vaccination. Results of the epidemiological model are then imputed in a health-economic model adapted to the Brazilian context. We perform deterministic and probabilistic sensitivity analysis to account for both epidemiological and economical sources of uncertainty.

RESULTS

Our results show that switching from TIV to QIV in the Brazilian pediatric population would prevent 406,600 symptomatic cases, 11,300 hospitalizations and almost 400 deaths by influenza season. This strategy would save 3400 life-years yearly for an incremental direct cost of R$169 million per year, down to R$86 million from a societal perspective. Incremental cost-effectiveness ratios for the switch would be R$49,700 per life-year saved and R$26,800 per quality-adjusted life-year gained from a public payer perspective, and even more cost-effective from a societal perspective. Our results are qualitatively similar in our sensitivity analysis.

CONCLUSIONS

Our analysis shows that switching from TIV to QIV to protect children aged 6mo to 5yo in the Brazilian influenza epidemiological context could have a strong public health impact and represent a cost-effective strategy from a public payer perspective, and a highly cost-effective one from a societal perspective.

Public health and economic impact of switching from a trivalent to a quadrivalent inactivated influenza vaccine in Mexico

Most influenza vaccines in Mexico are trivalent, containing two influenza A strains and a single B strain. Quadrivalent influenza vaccines (QIVs) extend protection by including an additional B strain to cover both co-circulating B lineages. Here, we retrospectively estimated how a switch to QIV in Mexico would have impacted influenza-related health outcomes over the 2010/2011 to 2015/2016 influenza seasons, and prospectively estimated the budget impact of using QIV in Mexico's national immunization program from 2016/2017 to 2020/2021. For the retrospective estimation, we used an age-stratified static model incorporating Mexico-specific input parameters. For the prospective estimation, we used a budget impact model based on retrospective attack rates considering predicted future vaccination coverage. Between 2010/2011 and 2015/2016, a switch to QIV would have prevented 270,596 additional influenza cases, 102,000 general practitioner consultations, 140,062 days of absenteeism, 3,323 hospitalizations, and 312 deaths, saving Mex$214 million (US$10.8 million) in third-party payer costs. In the prospective analysis, a switch to QIV was estimated to prevent an additional 225,497 influenza cases, 85,000 general practitioner consultations, 116,718 days of absenteeism, 2,769 hospitalizations, and 260 deaths, saving Mex$178 million (US$9 million) in third-party payer costs over 5 years. Compared to the trivalent vaccine, the benefit and costs saved with QIV were sensitive to the distribution of influenza A vs. B cases and trivalent vaccine effectiveness against the mismatched B strain. These results suggest switching to QIV in Mexico would benefit healthcare providers and society by preventing influenza cases, morbidity, and deaths, and reducing associated use of medical resources.

Influenza in the school-aged population in Mexico: burden of disease and cost-effectiveness of vaccination in children

BACKGROUND

The current national influenza vaccination schedule in Mexico does not recommend vaccination in the school-aged population (5-11 years). Currently, there are limited data from middle-income countries analysing the cost-effectiveness of influenza vaccination in this population. We explored the clinical effects and economic benefits of expanding the current national influenza vaccination schedule in Mexico to include the school-aged population.

METHODS

A static 1-year model incorporating herd effect was used to assess the cost-effectiveness of expanding the current national influenza vaccination schedule of Mexico to include the school-aged population. We performed a cross-sectional epidemiological study using influenza records (2009-2018), death records (2010-2015), and discharge and hospitalisation records (2010-2016), from the databases of Mexico's Influenza Surveillance System (SISVEFLU), the National Mortality Epidemiological and Statistical System (SEED), and the Automated Hospital Discharge System (SAEH), respectively. Cost estimates for influenza cases were based on 7 scenarios using data analysed from SISVEFLU; assumptions for clinical management of cases were defined according to Mexico's national clinical guidelines. The primary health outcome for this study was the number of influenza cases avoided. A sensitivity analysis was performed using conservative and optimistic parameters (vaccination coverage: 30% / 70%, Vaccine effectiveness: 19% / 68%).

RESULTS

It was estimated that expanding the influenza immunisation programme to cover school-aged population in Mexico over the 2018-2019 influenza season would result in 671,461 cases of influenza avoided (50% coverage and 50% effectiveness assumed). Associated with this were 262,800 fewer outpatient consultations; 154,100 fewer emergency room consultations; 97,600 fewer hospitalisations, and 15 fewer deaths. Analysis of cases avoided by age-group showed that 55.4% of them were in the school-aged population, and the decrease in outpatient consultations was largest in this population. There was an overall decrease in the economic burden for the Mexican health care system of 111.9 million US dollars; the immunization programme was determined to be cost-saving in the base, conservative and optimistic scenarios.

CONCLUSIONS

Vaccinating school-aged population in Mexico would be cost-effective; expansion of the current national vaccination schedule to this age group is supported.

Impact of funding influenza vaccination on coverage among Australian children: a national study using MedicineInsight, a large general practice database

Influenza contributes to morbidity and mortality worldwide. Children are at a higher risk of influenza-related complications and vaccination promotes direct protection and limits transmission. This study aimed to explore influenza vaccination coverage among children in Australian general practice from 2015 to 2018, and patterns in coverage before and after the implementation of state-funded immunization programs. Data from 196,520 'active' patients (3+ consultations in two consecutive years) aged <5 years from 542 Australian general practices were included (MedicineInsight database). Logistic regression models were used to identify associations between vaccination with patient and practice characteristics. The overall vaccination coverage increased more than five times from 2015 (3.9%) to 2018 (19.6%) and varied among states. Children attending practices located in the wealthiest areas were more likely to receive the vaccine and appeared to benefit most from the funding, as the increase in coverage from 2017 to 2018 was greater among them than those attending practices in the least advantaged areas (17 vs. 11 percentage points, respectively). This relationship was not evident when analyzing the patient's socioeconomic level. In conclusion, free influenza vaccinations increase coverage in at-risk populations. Promotional campaigns may be required to maintain higher coverage and target practices located in low-income areas.

The Epidemiology and Burden of Influenza B/Victoria and B/Yamagata Lineages in Kenya, 2012-2016

BACKGROUND

The impact of influenza B virus circulation in Sub-Saharan Africa is not well described.

METHODS

We analyzed data from acute respiratory illness (ARI) in Kenya. We assessed clinical features and age-specific hospitalization and outpatient visit rates by person-years for influenza B/Victoria and B/Yamagata and the extent to which circulating influenza B lineages in Kenya matched the vaccine strain component of the corresponding season (based on Northern Hemisphere [October-March] and Southern Hemisphere [April-September] vaccine availability).

RESULTS

From 2012 to 2016, influenza B represented 31% of all influenza-associated ARIs detected (annual range, 13-61%). Rates of influenza B hospitalization and outpatient visits were higher for <5 vs ≥5 years. Among <5 years, B/Victoria was associated with pneumonia hospitalization (64% vs 44%; P = .010) and in-hospital mortality (6% vs 0%; P = .042) compared with B/Yamagata, although the mean annual hospitalization rate for B/Victoria was comparable to that estimated for B/Yamagata. The 2 lineages co-circulated, and there were mismatches with available trivalent influenza vaccines in 2/9 seasons assessed.

CONCLUSIONS

Influenza B causes substantial burden in Kenya, particularly among children aged <5 years, in whom B/Victoria may be associated with increased severity. Our findings suggest a benefit from including both lineages when considering influenza vaccination in Kenya.

Influenza in Latin America: A report from the Global Influenza Initiative (GII)

The Global Influenza Initiative (GII) is a global expert group that aims to raise acceptance and uptake of influenza vaccines globally and provides recommendations and strategies to address challenges at local, national, regional, and global levels. This article provides a consolidated estimation of disease burden in Latin America, currently lacking in published literature, and delivers the GII recommendations specific to Latin America that provide guidance to combat existing vaccination challenges. While many countries worldwide, especially in the tropics and subtropics, do not have a seasonal influenza policy, 90% of Latin American countries have a seasonal influenza policy in place. Local governments in the Latin American countries and The Pan American Health Organization's Technical Advisory Group on Vaccine-preventable Diseases play a major role in improving the vaccination coverage and reducing the overall disease burden. Influenza seasonality poses the biggest challenge in deciding on optimal timing for vaccination in Latin America, as in temperate climates seasonal influenza activity peaks during the winter months (November-February and May-October) in the northern and southern hemispheres, respectively, while in the tropics and subtropical regions it usually occurs throughout the year, but especially during the rainy season. Besides this, vaccine mismatch with circulating strains, misconception concerning influenza vaccine effectiveness, and poor disease and vaccine awareness among the public are also key challenges that need to be overcome. Standardization of clinical case definitions is important across all Latin American countries. Surveillance (mostly passive) has improved substantially in the Latin American countries over the past decade, but more is still required to better understand the disease burden and help inform policies.

Latin American Adult Immunisation Advocacy Summit: Overcoming regional barriers to adult vaccination

Older adults in Latin America are at an increased risk of hospitalisation, ill health, catastrophic disability and death due to vaccine-preventable diseases such as influenza, herpes zoster, and pneumonia. The Latin American Adult Immunisation Advocacy Summit, held in Mexico City, gathered 40 experts in health, ageing and immunisation from 12 Latin American countries to explore good practices of adult vaccination, key country and regional barriers, and strategies to overcome these barriers. The Summit comprised of introductory lectures, plenary panels and breakout sessions with the overarching goal of improving adult vaccination uptake rates throughout the region. Several key messages and recommendations arose from the Summit. Delegates agreed upon the need for a paradigm shift in thinking towards a life course perspective on vaccination to sustain good health throughout life and promote well-being, dignity and functional capacity in older age. Delegates revealed the need for national financial commitment to fixed and irrevocable funding for universal vaccination and the urgent requirement for robust scientific, epidemiologic research in Latin American communities on the cost benefits of such coverage. The recommendations were strengthened through a common understanding of the unique multisectoral and multidisciplinary collaborations essential to influence and help shape public policy.

Cost Effectiveness of Quadrivalent Influenza Vaccines Compared with Trivalent Influenza Vaccines in Young Children and Older Adults in Korea

INTRODUCTION

Trivalent influenza vaccines (TIVs) are currently reimbursed for subjects aged ≥ 65 years and children between 6 and 59 months of age under a national immunization program in South Korea. Quadrivalent influenza vaccines (QIVs) are expected to address the potential problem of influenza B-lineage mismatch for TIVs.

OBJECTIVE

The objective of this analysis was to compare the cost effectiveness of QIV versus TIV in children aged 6-59 months and older adults ≥ 65 years of age in South Korea.

METHODS

A 1-year static population model was employed to compare the costs and outcomes of a QIV vaccination program compared with TIV in children aged 6-59 months and older adults ≥ 65 years of age in South Korea. Influenza-related parameters (probabilities, health resource use, and costs) were derived from an analysis of the National Health Insurance System claims database between 2010 and 2013 under a broad and narrow set of International Classification of Diseases, Tenth Revision (ICD-10) codes used to identify influenza. Other inputs were extracted from published literature. Incremental cost-effectiveness ratios (2016 South Korean Won [KRW] per quality-adjusted life-year [QALY] gained) were estimated using a 'limited' societal perspective as per the Korean pharmacoeconomic guidelines. QALYs lost due to premature mortality were discounted at 5% annually.

RESULTS

For both age groups combined, under the narrow definition of influenza, QIV is expected to prevent nearly 16,000 (2923 in children and 13,011 in older adults) medically attended influenza cases, nearly 8000 (672 in children, 7048 in older adults) cases of complications, and over 230 (0 in children, 238 in older adults) deaths annually compared with TIV. The impact of using QIV versus TIV in this setting translates into savings of KRW 24 billion (KRW 0.6 billion in children, KRW 23.4 billion in older adults) in annual medical costs, and over 2100 (18 in children, 2084 in older adults) QALYs. Under the broad definition, the corresponding results are over 190,000 (50,697 in children, 140,644 in older adults) influenza cases, over 37,000 (12,623 in children, 24,526 in older adults) complications, 270 deaths (0 in children, 270 in older adults), KRW 94.22 billion (KRW 16 billion in children, KRW 78.2 billion in older adults), and over 3500 QALYs saved (316 in children, 3260 in older adults).

CONCLUSION

The use of QIV over TIV was estimated to not be cost effective in children 6-59 months of age, but cost saving in older adults, using the narrow definition of influenza; however, QIV use was cost saving in both age groups using the broad definition. QIV is expected to yield more benefits in older adults ≥ 65 years of age than in children aged 6-59 months due to higher influenza-related mortality and costs among the older adults. Further analyses considering the indirect effects of influenza vaccination in children are required.

Quadrivalent influenza vaccines in low and middle income countries: Cost-effectiveness, affordability and availability

In high-income countries, there is an increased tendency to replace inactivated seasonal trivalent influenza (TIV) vaccines with quadrivalent (QIV) vaccines as these are considered to give a greater public health benefit. In addition, several recent studies from the USA and Europe indicate that replacement with QIV might also be cost-effective; however, the situation in low- and middle-income countries (LMIC) is less clear as few studies have investigated this aspect. The paper by de Boer et al. (2008) describes a dynamic modelling study commissioned by WHO that suggests that in LMICs, under certain conditions, QIV might also be more cost-effective than TIV. In this commentary, we discuss some important aspects that policymakers in LMICs might wish to take into account when considering replacing TIV by QIV. Indeed, from the data presented in the paper by de Boer et al. it can be inferred that replacing QIV for TIV would mean a 25-29% budget increase for seasonal influenza vaccination in South Africa and Vietnam, resulting in an incremental influenza-related health impact reduction of only 7-8% when a 10% symptomatic attack rate is assumed. We argue that national health budget considerations in LMIC might lead decision-makers to choose other investments with higher health impact for a budget equivalent to roughly a quarter of the yearly TIV immunization costs. In addition to an increased annual cost that would be associated with a decision to replace TIV with QIV, there would be an increased pressure on manufacturers to produce QIV in time for the influenza season requiring manufacturers to produce some components of the seasonal vaccine at risk prior to the WHO recommendations for influenza vaccines. Unless the current uncertainties, impracticalities and increased costs associated with QIVs are resolved, TIVs are likely to remain the more attractive option for many LMICs. Each country should establish its context-specific process for decision-making based on national data on disease burden and costs in order to determine whether the health gains out-weigh the additional cost of moving to QIV. For example, immunizing more people in the population, especially those in higher risk groups, with TIV might not only provide better value for money but also deliver better health outcomes in LMICs. Countries with local influenza vaccine manufacturing capacity should include in their seasonal influenza vaccine procurement process an analysis of the pros- and cons- of TIV versus QIV, to ensure both feasibility and sustainability of local manufacturing.

Quadrivalent inactivated influenza vaccine (VaxigripTetra™)

INTRODUCTION

VaxigripTetra™ (IIV4; Sanofi Pasteur) is a quadrivalent split-virion influenza vaccine approved in Europe in 2016 for individuals ≥ 3 years of age. IIV4 builds on the well-established record of the trivalent split-virion influenza vaccine (Vaxigrip®). Areas covered: This literature review summarizes the rationale for developing quadrivalent influenza vaccines and discusses the phase III clinical trial results supporting the immunogenicity, safety, and tolerability of IIV4. Expert commentary: IIV4 is immunogenic and well tolerated. Adding a second B strain to the trivalent split-virion influenza vaccine provides a superior immune response for the additional strain but does not reduce the immune response for the three other strains or negatively affect the safety profile. By offering broader protection against co-circulating influenza B lineages, IIV4 has the potential to further reduce influenza-related morbidity and mortality beyond that achieved with trivalent vaccines.