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Yang Q, Park SW, Saad-Roy CM, Ahmad I, Viboud C, Arinaminpathy N, Grenfell BT. Assessing population-level target product profiles of universal human influenza A vaccines. Epidemics 2024; 48:100776. [PMID: 38944025 DOI: 10.1016/j.epidem.2024.100776] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2024] [Revised: 05/22/2024] [Accepted: 06/07/2024] [Indexed: 07/01/2024] Open
Abstract
Influenza A has two hemagglutinin groups, with stronger cross-immunity to reinfection within than between groups. Here, we explore the implications of this heterogeneity for proposed cross-protective influenza vaccines that may offer broad, but not universal, protection. While the development goal for the breadth of human influenza A vaccine is to provide cross-group protection, vaccines in current development stages may provide better protection against target groups than non-target groups. To evaluate vaccine formulation and strategies, we propose a novel perspective: a vaccine population-level target product profile (PTPP). Under this perspective, we use dynamical models to quantify the epidemiological impacts of future influenza A vaccines as a function of their properties. Our results show that the interplay of natural and vaccine-induced immunity could strongly affect seasonal subtype dynamics. A broadly protective bivalent vaccine could lower the incidence of both groups and achieve elimination with sufficient vaccination coverage. However, a univalent vaccine at low vaccination rates could permit a resurgence of the non-target group when the vaccine provides weaker immunity than natural infection. Moreover, as a proxy for pandemic simulation, we analyze the invasion of a variant that evades natural immunity. We find that a future vaccine providing sufficiently broad and long-lived cross-group protection at a sufficiently high vaccination rate, could prevent pandemic emergence and lower the pandemic burden. This study highlights that as well as effectiveness, breadth and duration should be considered in epidemiologically informed TPPs for future human influenza A vaccines.
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Affiliation(s)
- Qiqi Yang
- Department of Ecology and Evolutionary Biology, Princeton University, NJ, USA.
| | - Sang Woo Park
- Department of Ecology and Evolutionary Biology, Princeton University, NJ, USA
| | - Chadi M Saad-Roy
- Miller Institute for Basic Research in Science, University of California, Berkeley, CA, USA; Department of Integrative Biology, University of California, Berkeley, CA, USA
| | - Isa Ahmad
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, School of Public Health, Imperial College London, UK
| | - Cécile Viboud
- Division of International Epidemiology and Population Studies, Fogarty International Center, National Institutes of Health, Bethesda, MD, USA
| | - Nimalan Arinaminpathy
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, School of Public Health, Imperial College London, UK
| | - Bryan T Grenfell
- Department of Ecology and Evolutionary Biology, Princeton University, NJ, USA; School of Public and International Affairs, Princeton University, NJ, USA
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2
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Saad-Roy CM, Levin SA, Grenfell BT, Boots M. Epidemiological impacts of post-infection mortality. Proc Biol Sci 2023; 290:20230343. [PMID: 37434526 PMCID: PMC10336371 DOI: 10.1098/rspb.2023.0343] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Accepted: 06/16/2023] [Indexed: 07/13/2023] Open
Abstract
Infectious diseases may cause some long-term damage to their host, leading to elevated mortality even after recovery. Mortality due to complications from so-called 'long COVID' is a stark illustration of this potential, but the impacts of such post-infection mortality (PIM) on epidemic dynamics are not known. Using an epidemiological model that incorporates PIM, we examine the importance of this effect. We find that in contrast to mortality during infection, PIM can induce epidemic cycling. The effect is due to interference between elevated mortality and reinfection through the previously infected susceptible pool. In particular, robust immunity (via decreased susceptibility to reinfection) reduces the likelihood of cycling; on the other hand, disease-induced mortality can interact with weak PIM to generate periodicity. In the absence of PIM, we prove that the unique endemic equilibrium is stable and therefore our key result is that PIM is an overlooked phenomenon that is likely to be destabilizing. Overall, given potentially widespread effects, our findings highlight the importance of characterizing heterogeneity in susceptibility (via both PIM and robustness of host immunity) for accurate epidemiological predictions. In particular, for diseases without robust immunity, such as SARS-CoV-2, PIM may underlie complex epidemiological dynamics especially in the context of seasonal forcing.
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Affiliation(s)
- Chadi M. Saad-Roy
- Miller Institute for Basic Research in Science, University of California, Berkeley, CA, USA
- Department of Integrative Biology, University of California, Berkeley, CA, USA
| | - Simon A. Levin
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA
| | - Bryan T. Grenfell
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA
- School of Public and International Affairs, Princeton University, Princeton, NJ, USA
| | - Mike Boots
- Department of Integrative Biology, University of California, Berkeley, CA, USA
- Department of Biosciences, University of Exeter, Penryn, UK
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3
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Waterlow NR, Radhakrishnan S, Dawa J, van Leeuwen E, Procter SR, Lambach P, Bresee J, Mazur M, Eggo RM, Jit M. Potential health and economic impact of paediatric vaccination using next-generation influenza vaccines in Kenya: a modelling study. BMC Med 2023; 21:106. [PMID: 36949456 PMCID: PMC10032252 DOI: 10.1186/s12916-023-02830-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Accepted: 01/30/2023] [Indexed: 03/24/2023] Open
Abstract
BACKGROUND Influenza is a major year-round cause of respiratory illness in Kenya, particularly in children under 5. Current influenza vaccines result in short-term, strain-specific immunity and were found in a previous study not to be cost-effective in Kenya. However, next-generation vaccines are in development that may have a greater impact and cost-effectiveness profile. METHODS We expanded a model previously used to evaluate the cost-effectiveness of seasonal influenza vaccines in Kenya to include next-generation vaccines by allowing for enhanced vaccine characteristics and multi-annual immunity. We specifically examined vaccinating children under 5 years of age with improved vaccines, evaluating vaccines with combinations of increased vaccine effectiveness, cross-protection between strains (breadth) and duration of immunity. We evaluated cost-effectiveness using incremental cost-effectiveness ratios (ICERs) and incremental net monetary benefits (INMBs) for a range of values for the willingness-to-pay (WTP) per DALY averted. Finally, we estimated threshold per-dose vaccine prices at which vaccination becomes cost-effective. RESULTS Next-generation vaccines can be cost-effective, dependent on the vaccine characteristics and assumed WTP thresholds. Universal vaccines (assumed to provide long-term and broad immunity) are most cost-effective in Kenya across three of four WTP thresholds evaluated, with the lowest median value of ICER per DALY averted ($263, 95% Credible Interval (CrI): $ - 1698, $1061) and the highest median INMBs. At a WTP of $623, universal vaccines are cost-effective at or below a median price of $5.16 per dose (95% CrI: $0.94, $18.57). We also show that the assumed mechanism underlying infection-derived immunity strongly impacts vaccine outcomes. CONCLUSIONS This evaluation provides evidence for country-level decision makers about future next-generation vaccine introduction, as well as global research funders about the potential market for these vaccines. Next-generation vaccines may offer a cost-effective intervention to reduce influenza burden in low-income countries with year-round seasonality like Kenya.
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Affiliation(s)
- Naomi R Waterlow
- Centre for Mathematical Modeling of Infectious Disease, London School of Hygiene and Tropical Medicine, London, WC14 7HT, UK.
| | - Sreejith Radhakrishnan
- Centre for Mathematical Modeling of Infectious Disease, London School of Hygiene and Tropical Medicine, London, WC14 7HT, UK
- School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow, G61 1QH, UK
| | - Jeanette Dawa
- Center for Epidemiological Modelling and Analysis, University of Nairobi, Nairobi, Kenya
- Washington State University - Global Health Kenya, Nairobi, Kenya
| | - Edwin van Leeuwen
- Centre for Mathematical Modeling of Infectious Disease, London School of Hygiene and Tropical Medicine, London, WC14 7HT, UK
- Statistics, Modelling and Economics Department, UK Health Security Agency, London, NW9 5EQ, UK
| | - Simon R Procter
- Centre for Mathematical Modeling of Infectious Disease, London School of Hygiene and Tropical Medicine, London, WC14 7HT, UK
| | - Philipp Lambach
- Immunization Vaccines and Biologicals Department, World Health Organization, Geneva, Switzerland
| | | | | | - Rosalind M Eggo
- Centre for Mathematical Modeling of Infectious Disease, London School of Hygiene and Tropical Medicine, London, WC14 7HT, UK
| | - Mark Jit
- Centre for Mathematical Modeling of Infectious Disease, London School of Hygiene and Tropical Medicine, London, WC14 7HT, UK
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McLeod DV, Gandon S. Effects of epistasis and recombination between vaccine-escape and virulence alleles on the dynamics of pathogen adaptation. Nat Ecol Evol 2022; 6:786-793. [PMID: 35437006 DOI: 10.1038/s41559-022-01709-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Accepted: 02/22/2022] [Indexed: 11/09/2022]
Abstract
Pathogen adaptation to public health interventions such as vaccination may take tortuous routes and involve multiple mutations at different locations in the pathogen genome, acting on distinct phenotypic traits. Yet how these multi-locus adaptations jointly evolve is poorly understood. Here we consider the joint evolution of two adaptations: pathogen escape from the vaccine-induced immune response and adjustments to pathogen virulence affecting transmission or clearance. We elucidate the role played by epistasis and recombination, with an emphasis on the different protective effects of vaccination. We show that vaccines blocking infection, reducing transmission and/or increasing clearance generate positive epistasis between the vaccine-escape and virulence alleles, favouring strains that carry both mutations, whereas vaccines reducing virulence mortality generate negative epistasis, favouring strains that carry either mutation but not both. High rates of recombination can affect these predictions. If epistasis is positive, frequent recombination can prevent the transient build-up of more virulent escape strains. If epistasis is negative, frequent recombination between loci can create an evolutionary bistability, favouring whichever adaptation is more accessible. Our work provides a timely alternative to the variant-centred perspective on pathogen adaptation and captures the effect of different types of vaccine on the interference between multiple adaptive mutations.
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Affiliation(s)
- David V McLeod
- CEFE, CNRS, Univ Montpellier, EPHE, IRD, Montpellier, France. .,Institute of Ecology and Evolution, Universität Bern, Bern, Switzerland. .,Swiss Institute of Bioinformatics, Lausanne, Switzerland.
| | - Sylvain Gandon
- CEFE, CNRS, Univ Montpellier, EPHE, IRD, Montpellier, France.
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5
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Ullah S, Ross TM. Next generation live-attenuated influenza vaccine platforms. Expert Rev Vaccines 2022; 21:1097-1110. [PMID: 35502639 DOI: 10.1080/14760584.2022.2072301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
INTRODUCTION Influenza virus is a major cause of seasonal epidemics and intermittent pandemics. Despite the current molecular biology and vaccine development, influenza virus infection is a significant burden. Vaccines are considered an essential countermeasure for effective control and prevention of influenza virus infection. Even though current influenza virus vaccines provide efficient protection against seasonal influenza outbreaks, the efficacy of these vaccines is not suitable due to antigenic changes of the viruses. AREAS COVERED This review focuses on different live-attenuated platforms for influenza virus vaccine development and proposes essential considerations for a rational universal influenza virus vaccine design. EXPERT OPINION Despite the recent efforts for universal influenza virus vaccines, there is a lack of broadly reactive antibodies' induction that can confer broad and long-lasting protection. Various strategies using live-attenuated influenza virus vaccines (LAIVs) are investigated to induce broadly reactive, durable, and cross-protective immune responses. LAIVs based on NS segment truncation prevent influenza virus infection and have shown to be effective vaccine candidates among other vaccine platforms. Although many approaches have been used for LAIVs generation, there is still a need to focus on the LAIVs development platforms to generate a universal influenza virus vaccine candidate.
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Affiliation(s)
- Subhan Ullah
- Center for Vaccines and Immunology, University of Georgia, Athens, Georgia, USA
| | - Ted M Ross
- Center for Vaccines and Immunology, University of Georgia, Athens, Georgia, USA.,Department of Infectious Diseases, University of Georgia, Athens, Georgia, USA
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Jang YH, Seong BL. Immune Responses Elicited by Live Attenuated Influenza Vaccines as Correlates of Universal Protection against Influenza Viruses. Vaccines (Basel) 2021; 9:vaccines9040353. [PMID: 33916924 PMCID: PMC8067561 DOI: 10.3390/vaccines9040353] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2021] [Revised: 04/05/2021] [Accepted: 04/06/2021] [Indexed: 02/06/2023] Open
Abstract
Influenza virus infection remains a major public health challenge, causing significant morbidity and mortality by annual epidemics and intermittent pandemics. Although current seasonal influenza vaccines provide efficient protection, antigenic changes of the viruses often significantly compromise the protection efficacy of vaccines, rendering most populations vulnerable to the viral infection. Considerable efforts have been made to develop a universal influenza vaccine (UIV) able to confer long-lasting and broad protection. Recent studies have characterized multiple immune correlates required for providing broad protection against influenza viruses, including neutralizing antibodies, non-neutralizing antibodies, antibody effector functions, T cell responses, and mucosal immunity. To induce broadly protective immune responses by vaccination, various strategies using live attenuated influenza vaccines (LAIVs) and novel vaccine platforms are under investigation. Despite superior cross-protection ability, very little attention has been paid to LAIVs for the development of UIV. This review focuses on immune responses induced by LAIVs, with special emphasis placed on the breadth and the potency of individual immune correlates. The promising prospect of LAIVs to serve as an attractive and reliable vaccine platforms for a UIV is also discussed. Several important issues that should be addressed with respect to the use of LAIVs as UIV are also reviewed.
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Affiliation(s)
- Yo Han Jang
- Department of Biological Sciences and Biotechnology Major in Bio-Vaccine Engineering, Andong National University, Andong 1375, Korea;
- Vaccine Industry Research Institute, Andong National University, Andong 1375, Korea
| | - Baik L. Seong
- Department of Biotechnology, College of Life Science and Biotechnology, Yonsei University, Seoul 03722, Korea
- Vaccine Innovation Technology Alliance (VITAL)-Korea, Yonsei University, Seoul 03722, Korea
- Correspondence: ; Tel.: +82-2-2123-7416
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Saad-Roy CM, Grenfell BT, Levin SA, Pellis L, Stage HB, van den Driessche P, Wingreen NS. Superinfection and the evolution of an initial asymptomatic stage. ROYAL SOCIETY OPEN SCIENCE 2021; 8:202212. [PMID: 33614103 PMCID: PMC7890506 DOI: 10.1098/rsos.202212] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Accepted: 12/16/2020] [Indexed: 06/12/2023]
Abstract
Pathogens have evolved a variety of life-history strategies. An important strategy consists of successful transmission by an infected host before the appearance of symptoms, that is, while the host is still partially or fully asymptomatic. During this initial stage of infection, it is possible for another pathogen to superinfect an already infected host and replace the previously infecting pathogen. Here, we study the effect of superinfection during the first stage of an infection on the evolutionary dynamics of the degree to which the host is asymptomatic (host latency) in that same stage. We find that superinfection can lead to major differences in evolutionary behaviour. Most strikingly, the duration of immunity following infection can significantly influence pathogen evolutionary dynamics, whereas without superinfection the outcomes are independent of host immunity. For example, changes in host immunity can drive evolutionary transitions from a fully symptomatic to a fully asymptomatic first infection stage. Additionally, if superinfection relative to susceptible infection is strong enough, evolution can lead to a unique strategy of latency that corresponds to a local fitness minimum, and is therefore invasible by nearby mutants. Thus, this strategy is a branching point, and can lead to coexistence of pathogens with different latencies. Furthermore, in this new framework with superinfection, we also find that there can exist two interior singular strategies. Overall, new evolutionary outcomes can cascade from superinfection.
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Affiliation(s)
- Chadi M. Saad-Roy
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA
| | - Bryan T. Grenfell
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA
- Princeton School of Public and International Affairs, Princeton University, Princeton, NJ, USA
- Division of International Epidemiology and Population Studies, Fogarty International Center, National Institutes of Health, Bethesda, MD, USA
| | - Simon A. Levin
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA
| | - Lorenzo Pellis
- Department of Mathematics, University of Manchester, Manchester, UK
- The Alan Turing Institute, London, UK
| | - Helena B. Stage
- Department of Mathematics, University of Manchester, Manchester, UK
| | - P. van den Driessche
- Department of Mathematics and Statistics, University of Victoria, Victoria, British Columbia, Canada
| | - Ned S. Wingreen
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
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8
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Wagner CE, Prentice JA, Saad-Roy CM, Yang L, Grenfell BT, Levin SA, Laxminarayan R. Economic and Behavioral Influencers of Vaccination and Antimicrobial Use. Front Public Health 2020; 8:614113. [PMID: 33409264 PMCID: PMC7779682 DOI: 10.3389/fpubh.2020.614113] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Accepted: 12/01/2020] [Indexed: 01/07/2023] Open
Abstract
Despite vast improvements in global vaccination coverage during the last decade, there is a growing trend in vaccine hesitancy and/or refusal globally. This has implications for the acceptance and coverage of a potential vaccine against COVID-19. In the United States, the number of children exempt from vaccination for “philosophical belief-based” non-medical reasons increased in 12 of the 18 states that allowed this policy from 2009 to 2017 (1). Meanwhile, the overuse and misuse of antibiotics, especially in young children, have led to increasing rates of drug resistance that threaten our ability to treat infectious diseases. Vaccine hesitancy and antibiotic overuse exist side-by-side in the same population of young children, and it is unclear why one modality (antibiotics) is universally seen as safe and effective, while the other (vaccines) is seen as potentially hazardous by some. In this review, we consider the drivers shaping the use of vaccines and antibiotics in the context of three factors: individual incentives, risk perceptions, and social norms and group dynamics. We illustrate how these factors contribute to the societal and individual costs of vaccine underuse and antimicrobial overuse. Ultimately, we seek to understand these factors that are at the nexus of infectious disease epidemiology and social science to inform policy-making.
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Affiliation(s)
- Caroline E Wagner
- Department of Bioengineering, McGill University, Montreal, QC, Canada
| | - Joseph A Prentice
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, United States
| | - Chadi M Saad-Roy
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, United States.,Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, United States
| | - Luojun Yang
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, United States
| | - Bryan T Grenfell
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, United States.,Princeton School of Public and International Affairs, Princeton University, Princeton, NJ, United States.,Fogarty International Center, National Institutes of Health, Bethesda, MD, United States
| | - Simon A Levin
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, United States.,Princeton Environmental Institute, Princeton University, Princeton, NJ, United States
| | - Ramanan Laxminarayan
- Princeton Environmental Institute, Princeton University, Princeton, NJ, United States.,Center for Disease Dynamics, Economics & Policy, Washington, DC, United States
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Viboud C, Gostic K, Nelson MI, Price GE, Perofsky A, Sun K, Sequeira Trovão N, Cowling BJ, Epstein SL, Spiro DJ. Beyond clinical trials: Evolutionary and epidemiological considerations for development of a universal influenza vaccine. PLoS Pathog 2020; 16:e1008583. [PMID: 32970783 PMCID: PMC7514029 DOI: 10.1371/journal.ppat.1008583] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The prospect of universal influenza vaccines is generating much interest and research at the intersection of immunology, epidemiology, and viral evolution. While the current focus is on developing a vaccine that elicits a broadly cross-reactive immune response in clinical trials, there are important downstream questions about global deployment of a universal influenza vaccine that should be explored to minimize unintended consequences and maximize benefits. Here, we review and synthesize the questions most relevant to predicting the population benefits of universal influenza vaccines and discuss how existing information could be mined to begin to address these questions. We review three research topics where computational modeling could bring valuable evidence: immune imprinting, viral evolution, and transmission. We address the positive and negative consequences of imprinting, in which early childhood exposure to influenza shapes and limits immune responses to future infections via memory of conserved influenza antigens. However, the mechanisms at play, their effectiveness, breadth of protection, and the ability to "reprogram" already imprinted individuals, remains heavily debated. We describe instances of rapid influenza evolution that illustrate the plasticity of the influenza virus in the face of drug pressure and discuss how novel vaccines could introduce new selective pressures on the evolution of the virus. We examine the possible unintended consequences of broadly protective (but infection-permissive) vaccines on the dynamics of epidemic and pandemic influenza, compared to conventional vaccines that have been shown to provide herd immunity benefits. In conclusion, computational modeling offers a valuable tool to anticipate the benefits of ambitious universal influenza vaccine programs, while balancing the risks from endemic influenza strains and unpredictable pandemic viruses. Moving forward, it will be important to mine the vast amount of data generated in clinical studies of universal influenza vaccines to ensure that the benefits and consequences of these vaccine programs have been carefully modeled and explored.
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Affiliation(s)
- Cécile Viboud
- Division of International Epidemiology and Population Studies, Fogarty International Center, National Institutes of Health, Bethesda, Maryland, United States
- * E-mail:
| | - Katelyn Gostic
- Dept. of Ecology and Evolutionary Biology, University of California, Los Angeles, Los Angeles, California, United States
- Dept. of Ecology and Evolution, University of Chicago, Chicago, Illinois, United States
| | - Martha I. Nelson
- Division of International Epidemiology and Population Studies, Fogarty International Center, National Institutes of Health, Bethesda, Maryland, United States
| | - Graeme E. Price
- Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, Maryland, United States
| | - Amanda Perofsky
- Division of International Epidemiology and Population Studies, Fogarty International Center, National Institutes of Health, Bethesda, Maryland, United States
| | - Kaiyuan Sun
- Division of International Epidemiology and Population Studies, Fogarty International Center, National Institutes of Health, Bethesda, Maryland, United States
| | - Nídia Sequeira Trovão
- Division of International Epidemiology and Population Studies, Fogarty International Center, National Institutes of Health, Bethesda, Maryland, United States
| | - Benjamin J. Cowling
- World Health Organization Collaborating Centre for Infectious Disease Epidemiology and Control, School of Public Health, The University of Hong Kong, Hong Kong Special Administrative Region, China
| | - Suzanne L. Epstein
- Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, Maryland, United States
| | - David J. Spiro
- Division of International Epidemiology and Population Studies, Fogarty International Center, National Institutes of Health, Bethesda, Maryland, United States
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