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Bolton KJ, McCaw JM, Dafilis MP, McVernon J, Heffernan JM. Seasonality as a driver of pH1N12009 influenza vaccination campaign impact. Epidemics 2023; 45:100730. [PMID: 38056164 DOI: 10.1016/j.epidem.2023.100730] [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: 03/28/2023] [Revised: 07/18/2023] [Accepted: 11/16/2023] [Indexed: 12/08/2023] Open
Abstract
Although the most recent respiratory virus pandemic was triggered by a Coronavirus, sustained and elevated prevalence of highly pathogenic avian influenza viruses able to infect mammalian hosts highlight the continued threat of pandemics of influenza A virus (IAV) to global health. Retrospective analysis of pandemic outcomes, including comparative investigation of intervention efficacy in different regions, provide important contributions to the evidence base for future pandemic planning. The swine-origin IAV pandemic of 2009 exhibited regional variation in onset, infection dynamics and annual infection attack rates (IARs). For example, the UK experienced three severe peaks of infection over two influenza seasons, whilst Australia experienced a single severe wave. We adopt a seasonally forced 2-subtype model for the transmission of pH1N12009 and seasonal H3N2 to examine the role vaccination campaigns may play in explaining differences in pandemic trajectories in temperate regions. Our model differentiates between the nature of vaccine- and infection-acquired immunity. In particular, we assume that immunity triggered by infection elicits heterologous cross-protection against viral shedding in addition to long-lasting neutralising antibody, whereas vaccination induces imperfect reduction in susceptibility. We employ an Approximate Bayesian Computation (ABC) framework to calibrate the model using data for pH1N12009 seroprevalence, relative subtype dominance, and annual IARs for Australia and the UK. Heterologous cross-protection substantially suppressed the pandemic IAR over the posterior, with the strength of protection against onward transmission inversely correlated with the initial reproduction number. We show that IAV pandemic timing relative to the usual seasonal influenza cycle influenced the size of the initial waves of pH1N12009 in temperate regions and the impact of vaccination campaigns.
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Affiliation(s)
- Kirsty J Bolton
- School of Mathematical Sciences, University of Nottingham, University Park, Nottingham, NG7 2RD, UK.
| | - James M McCaw
- School of Mathematics and Statistics, The University of Melbourne, Parkville, Australia; Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Parkville, Australia
| | - Mathew P Dafilis
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Parkville, Australia
| | - Jodie McVernon
- Peter Doherty Institute for Infection and Immunity, The Royal Melbourne Hospital and The University of Melbourne, Parkville, Australia
| | - Jane M Heffernan
- Centre for Disease Modelling, Mathematics & Statistics, York University, Canada
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Pendrey CG, Strachan J, Peck H, Aziz A, Moselen J, Moss R, Rahaman MR, Barr IG, Subbarao K, Sullivan SG. The re-emergence of influenza following the COVID-19 pandemic in Victoria, Australia, 2021 to 2022. Euro Surveill 2023; 28:2300118. [PMID: 37707981 PMCID: PMC10687983 DOI: 10.2807/1560-7917.es.2023.28.37.2300118] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Accepted: 06/28/2023] [Indexed: 09/16/2023] Open
Abstract
BackgroundCOVID-19 pandemic mitigation measures, including travel restrictions, limited global circulation of influenza viruses. In Australia, travel bans for non-residents and quarantine requirements for returned travellers were eased in November 2021, providing pathways for influenza viruses to be re-introduced.AimWe aimed to describe the epidemiological and virological characteristics of the re-emergence of influenza in Victoria, Australia to inform public health interventions.MethodsFrom 1 November 2021 to 30 April 2022, we conducted an epidemiological study analysing case notification data from the Victorian Department of Health to describe case demographics, interviewed the first 200 cases to establish probable routes of virus reintroduction and examined phylogenetic and antigenic data to understand virus diversity and susceptibility to current vaccines.ResultsOverall, 1,598 notifications and 1,064 positive specimens were analysed. The majority of cases (61.4%) occurred in the 15-34 years age group. Interviews revealed a higher incidence of international travel exposure during the first month of case detections, and high levels of transmission in university residential colleges were associated with return to campus. Influenza A(H3N2) was the predominant subtype, with a single lineage predominating despite multiple importations.ConclusionEnhanced testing for respiratory viruses during the COVID-19 pandemic provided a more complete picture of influenza virus transmission compared with previous seasons. Returned international travellers were important drivers of influenza reemergence, as were young adults, a group whose role has previously been under-recognised in the establishment of seasonal influenza epidemics. Targeting interventions, including vaccination, to these groups could reduce future influenza transmission.
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Affiliation(s)
- Catherine Ga Pendrey
- WHO Collaborating Centre for Reference and Research on Influenza, Royal Melbourne Hospital, at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia
- National Centre for Epidemiology and Population Health, Australian National University, Canberra, Australia
- Communicable Diseases, Health Protection Branch, Public Health Division, Department of Health, Victoria, Melbourne, Australia
| | - Janet Strachan
- Communicable Diseases, Health Protection Branch, Public Health Division, Department of Health, Victoria, Melbourne, Australia
| | - Heidi Peck
- WHO Collaborating Centre for Reference and Research on Influenza, Royal Melbourne Hospital, at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia
| | - Ammar Aziz
- WHO Collaborating Centre for Reference and Research on Influenza, Royal Melbourne Hospital, at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia
| | - Jean Moselen
- WHO Collaborating Centre for Reference and Research on Influenza, Royal Melbourne Hospital, at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia
| | - Rob Moss
- School of Population and Global Health, University of Melbourne, Melbourne, Australia
| | - Md Rezanur Rahaman
- National Centre for Epidemiology and Population Health, Australian National University, Canberra, Australia
| | - Ian G Barr
- WHO Collaborating Centre for Reference and Research on Influenza, Royal Melbourne Hospital, at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia
- Department of Immunology and Microbiology, University of Melbourne, at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia
| | - Kanta Subbarao
- WHO Collaborating Centre for Reference and Research on Influenza, Royal Melbourne Hospital, at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia
- Department of Immunology and Microbiology, University of Melbourne, at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia
| | - Sheena G Sullivan
- WHO Collaborating Centre for Reference and Research on Influenza, Royal Melbourne Hospital, at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia
- Communicable Diseases, Health Protection Branch, Public Health Division, Department of Health, Victoria, Melbourne, Australia
- Department of Infectious Diseases, University of Melbourne, at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia
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Characterization of T cell receptors reactive to HCRT NH2, pHA 273-287, and NP 17-31 in control and narcolepsy patients. Proc Natl Acad Sci U S A 2022; 119:e2205797119. [PMID: 35914171 PMCID: PMC9371724 DOI: 10.1073/pnas.2205797119] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Narcolepsy type 1 (NT1), a disorder caused by hypocretin/orexin (HCRT) cell loss, is associated with human leukocyte antigen (HLA)-DQ0602 (98%) and T cell receptor (TCR) polymorphisms. Increased CD4+ T cell reactivity to HCRT, especially DQ0602-presented amidated C-terminal HCRT (HCRTNH2), has been reported, and homology with pHA273-287 flu antigens from pandemic 2009 H1N1, an established trigger of the disease, suggests molecular mimicry. In this work, we extended DQ0602 tetramer and dextramer data to 77 cases and 44 controls, replicating our prior finding and testing 709 TCRs in Jurkat 76 T cells for functional activation. We found that fewer TCRs isolated with HCRTNH2 (∼11%) versus pHA273-287 or NP17-31 antigens (∼50%) were activated by their ligand. Single-cell characterization did not reveal phenotype differences in influenza versus HCRTNH2-reactive T cells, and analysis of TCR CDR3αβ sequences showed TCR clustering by responses to antigens but no cross-peptide class reactivity. Our results do not support the existence of molecular mimicry between HCRT and pHA273-287 or NP17-31.
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A method for estimating the transmissibility of influenza using serial cross-sectional seroepidemiological data. J Theor Biol 2020; 511:110566. [PMID: 33347894 DOI: 10.1016/j.jtbi.2020.110566] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Revised: 12/09/2020] [Accepted: 12/11/2020] [Indexed: 11/22/2022]
Abstract
BACKGROUND Seroepidemiological surveillance data has been demonstrated to be useful for estimating the cumulative incidence of influenza, and measures the difference between pre- and post-epidemic seropositive fractions. Despite this, such studies relied on a chosen cut-off value for seropositivity. The aim of the present study is to develop a method to analyze distributions of serial cross-sectional seroepidemiological surveillance datasets using an epidemiological model so that the transmission potential can be estimated without imposing a cut-off value. METHODS A mathematical model of influenza transmission with a discrete antibody titer level was constructed. The final size equation for pre- and post-epidemic titer levels was derived. Subsequently, using the estimated distribution of the dilution increase caused by infection and the measurement error distribution, the model parameters were optimized using the maximum likelihood method. A bootstrap-based confidence interval calculation and sensitivity analysis were also performed. RESULTS Without imposing a cut-off value, the cumulative incidence was quantified, thereby yielding an estimate of the basic reproduction number. For the purpose of exposition, the proposed method was applied to influenza A/Victoria/3/75(H3N2) data, and serological data between 1975 and 1976 were compared. The estimated reproduction number was greater than that using the cut-off value of the hemagglutination inhibition level with titer level 20 (dilution 1:20) or above to define positives. CONCLUSION The proposed method without a cut-off value offers an unbiased approach to estimating the cumulative incidence along with the reproduction number. If a cut-off value is required, the results imply that titer level 20 or above may better represent a reasonable cut-off value for calculating the incidence, but it could underestimate the basic reproduction number.
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Mahallawi WH, Ibrahim NA, Alahmadi KS, Al-Harbi AK, Almughthawi MA, Alhazmi OA, Alsehli FH, Khabour OF. Natural immunity to influenza A and B among Saudi blood donors in Al Madinah Al Munawarah, Saudi Arabia. Saudi Med J 2020; 41:1301-1307. [PMID: 33294887 PMCID: PMC7841591 DOI: 10.15537/smj.2020.12.05582] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Objectives: To investigate the seroprevalence of influenza viruses (A and B) among blood donors in Kingdom of Saudi Arabia. Methods: The present investigation was conducted between April 2019 and July 2019. Participants were healthy adults recruited from the central blood bank Al Madinah Al Munawarah, Kingdom of Saudi Arabia. Immunoglobulin G (IgG) levels against influenza A and B were measured in serum samples using ELISA. Results: The results showed that 29.2% of the sample had significant concentrations of influenza A IgG antibody, whereas 38.6% had significant concentrations of influenza B IgG antibody. A strong correlation was found between the levels of influenza A and influenza B antibodies (r=0.708, p<0.001). The number of individuals identified as negative for influenza A IgG antibody increased with age (p<0.01). In addition, no correlations were identified between influenza A IgG and influenza B IgG and body mass index (BMI), (p>0.05). Finally, linear regression analysis showed that the level of influenza A antibody can be predicted by age (p<0.05) and body mass index (BMI) (p<0.05). Conclusion: Approximately one-third of Saudi Arabian adults presented significant levels of influenza A and B antibodies in our study. Demographic factors, including age and BMI, might contribute to influenza A antibody levels.
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Affiliation(s)
- Waleed H Mahallawi
- Department of Medical Laboratory Technology, College of Applied Medical Sciences, Taibah University, Al Madinah Al Munawarah, Kingdom of Saudi Arabia. E-mail.
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Zhang Y, Leung K, Perera RAPM, Lee CK, Peiris JSM, Wu JT. Harnessing the potential of blood donation archives for influenza surveillance and control. PLoS One 2020; 15:e0233605. [PMID: 32470010 PMCID: PMC7259782 DOI: 10.1371/journal.pone.0233605] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Accepted: 05/10/2020] [Indexed: 02/04/2023] Open
Abstract
Many blood donation services around the globe maintain large archives of serum and/or plasma specimens of blood donations which could potentially be used for serologic surveillance and risk assessment of influenza. Harnessing this potential requires robust evidence that the outcomes of influenza serology in plasma, which is rarely used, is consistent with that in serum, which is the conventional choice of specimens for influenza serology. We harvested EDTA-plasma specimens from the blood donation archives of Hong Kong Red Cross Transfusion Services, where EDTA is the type of anticoagulant used for plasma collection, compared their antibody titers and responses to that in serum. Influenza A/H1N1/California/7/2009 and A/H3N2/Victoria/208/2009 were the test strains. Our results showed that antibody titers in 609 matched serum/EDTA-plasma specimens (i.e. obtained from the same donor at the same time) had good agreement inferred by Intraclass Correlation Coefficient, the value of which was 0.82 (95% CI: 0.77-0.86) for hemagglutination inhibition assay and 0.95 (95% CI: 0.93-0.96) for microneutralization assay; seroconversion rates (based on hemagglutination inhibition titers) during the 2010 and 2011 influenza seasons in Hong Kong inferred from paired EDTA-plasma were similar to that inferred from paired sera. Our study provided the proof-of-concept that blood donation archives could be leveraged as a valuable source of longitudinal blood specimens for the surveillance, control and risk assessment of both pandemic and seasonal influenza.
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Affiliation(s)
- Yanyu Zhang
- School of Public Health, WHO Collaborating Center for Infectious Disease Epidemiology and Control, The University of Hong Kong, Hong Kong Special Administrative Region, China
| | - Kathy Leung
- School of Public Health, WHO Collaborating Center for Infectious Disease Epidemiology and Control, The University of Hong Kong, Hong Kong Special Administrative Region, China
| | - Ranawaka A. P. M. Perera
- Center of Influenza Research and School of Public Health, The University of Hong Kong, Hong Kong Special Administrative Region, China
| | - Cheuk-Kwong Lee
- Hong Kong Red Cross Blood Transfusion Service, Hospital Authority, Hong Kong Special Administrative Region, China
| | - J. S. Malik Peiris
- Center of Influenza Research and School of Public Health, The University of Hong Kong, Hong Kong Special Administrative Region, China
| | - Joseph T. Wu
- School of Public Health, WHO Collaborating Center for Infectious Disease Epidemiology and Control, The University of Hong Kong, Hong Kong Special Administrative Region, China
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Assessing the Low Influenza Vaccination Coverage Rate Among Healthcare Personnel in India: A Review of Obstacles, Beliefs, and Strategies. Value Health Reg Issues 2020; 21:100-104. [DOI: 10.1016/j.vhri.2019.08.480] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2018] [Revised: 08/21/2019] [Accepted: 08/27/2019] [Indexed: 11/20/2022]
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McVernon J, Sorrell TC, Firman J, Murphy B, Lewin SR. Is Australia prepared for the next pandemic? Med J Aust 2018; 206:284-286. [PMID: 28403754 DOI: 10.5694/mja16.01451] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Accepted: 02/16/2017] [Indexed: 11/17/2022]
Affiliation(s)
- Jodie McVernon
- Victorian Infectious Diseases Reference Laboratory, The Peter Doherty Institute for Infection and Immunity, Royal Melbourne Hospital and University of Melbourne, Melbourne, VIC
| | - Tania C Sorrell
- Marie Bashir Institute for Infectious Diseases and Biosecurity, University of Sydney, Sydney, NSW
| | - Jenny Firman
- Office of Health Protection, Australian Government Department of Health, Canberra, ACT
| | - Brendan Murphy
- Office of Health Protection, Australian Government Department of Health, Canberra, ACT
| | - Sharon R Lewin
- The Peter Doherty Institute for Infection and Immunity, Royal Melbourne Hospital and University of Melbourne, Melbourne, VIC
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9
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Moss R, McCaw JM, Cheng AC, Hurt AC, McVernon J. Reducing disease burden in an influenza pandemic by targeted delivery of neuraminidase inhibitors: mathematical models in the Australian context. BMC Infect Dis 2016; 16:552. [PMID: 27724915 PMCID: PMC5057455 DOI: 10.1186/s12879-016-1866-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Accepted: 09/23/2016] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND Many nations maintain stockpiles of neuraminidase inhibitor (NAI) antiviral agents for use in influenza pandemics to reduce transmission and mitigate the course of clinical infection. Pandemic preparedness plans include the use of these stockpiles to deliver proportionate responses, informed by emerging evidence of clinical impact. Recent uncertainty about the effectiveness of NAIs has prompted these nations to reconsider the role of NAIs in pandemic response, with implications for pandemic planning and for NAI stockpile size. METHODS We combined a dynamic model of influenza epidemiology with a model of the clinical care pathways in the Australian health care system to identify effective NAI strategies for reducing morbidity and mortality in pandemic events, and the stockpile requirements for these strategies. The models were informed by a 2015 assessment of NAI effectiveness against susceptibility, pathogenicity, and transmission of influenza. RESULTS Liberal distribution of NAIs for early treatment in outpatient settings yielded the greatest benefits in all of the considered scenarios. Restriction of community-based treatment to risk groups was effective in those groups, but failed to prevent the large proportion of cases arising from lower risk individuals who comprise the majority of the population. CONCLUSIONS These targeted strategies are only effective if they can be deployed within the constraints of existing health care infrastructure. This finding highlights the critical importance of identifying optimal models of care delivery for effective emergency health care response.
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Affiliation(s)
- Robert Moss
- Modelling and Simulation Unit Centre for Epidemiology and Biostatistics Melbourne School of Population and Global Health, The University of Melbourne, Level 3, 207 Bouverie St, Melbourne, 3010, Victoria, Australia.
| | - James M McCaw
- Modelling and Simulation Unit Centre for Epidemiology and Biostatistics Melbourne School of Population and Global Health, The University of Melbourne, Level 3, 207 Bouverie St, Melbourne, 3010, Victoria, Australia.,School of Mathematics and Statistics, The University of Melbourne, Melbourne, Australia.,Murdoch Childrens Research Institute, Melbourne, Australia
| | - Allen C Cheng
- Infectious Disease Epidemiology Unit, Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Australia.,Infection Prevention and Healthcare Epidemiology Unit, Alfred Health, Melbourne, Australia
| | - Aeron C Hurt
- WHO Collaborating Centre for Reference and Research on Influenza, Peter Doherty Institute, Melbourne, Australia
| | - Jodie McVernon
- Modelling and Simulation Unit Centre for Epidemiology and Biostatistics Melbourne School of Population and Global Health, The University of Melbourne, Level 3, 207 Bouverie St, Melbourne, 3010, Victoria, Australia.,Murdoch Childrens Research Institute, Melbourne, Australia
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Sunagawa S, Iha Y, Taira K, Okano S, Kinjo T, Higa F, Kuba K, Tateyama M, Nakamura K, Nakamura S, Motooka D, Horii T, Parrott GL, Fujita J. An Epidemiological Analysis of Summer Influenza Epidemics in Okinawa. Intern Med 2016; 55:3579-3584. [PMID: 27980256 PMCID: PMC5283956 DOI: 10.2169/internalmedicine.55.7107] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Objective This study evaluates the difference between winter influenza and summer influenza in Okinawa. Methods From January 2007 to June 2014, weekly rapid antigen test (RAT) results performed in four acute care hospitals were collected for the surveillance of regional influenza prevalence in the Naha region of the Okinawa Islands. Results An antigenic data analysis revealed that multiple H1N1 and H3N2 viruses consistently co-circulate in Okinawa, creating synchronized seasonal patterns and a high genetic diversity of influenza A. Additionally, influenza B viruses play a significant role in summer epidemics, almost every year. To further understand influenza epidemics during the summer in Okinawa, we evaluated the full genome sequences of some representative human influenza A and influenza B viruses isolated in Okinawa. Phylogenetic data analysis also revealed that multiple H1N1 and H3N2 viruses consistently co-circulate in Okinawa. Conclusion This surveillance revealed a distinct epidemic pattern of seasonal and pandemic influenza in this subtropical region.
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Affiliation(s)
- Satoko Sunagawa
- Department of Infectious, Respiratory, and Digestive Medicine, Control and Prevention of Infectious Diseases, Faculty of Medicine, University of the Ryukyus, Japan
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Affiliation(s)
- Baijayantimala Mishra
- Department of Microbiology, All India Institute of Medical Sciences, Bhubaneswar, Odisha, India
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12
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Bolton KJ, McCaw JM, Brown L, Jackson D, Kedzierska K, McVernon J. Prior population immunity reduces the expected impact of CTL-inducing vaccines for pandemic influenza control. PLoS One 2015; 10:e0120138. [PMID: 25811654 PMCID: PMC4374977 DOI: 10.1371/journal.pone.0120138] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2014] [Accepted: 02/04/2015] [Indexed: 11/18/2022] Open
Abstract
Vaccines that trigger an influenza-specific cytotoxic T cell (CTL) response may aid pandemic control by limiting the transmission of novel influenza A viruses (IAV). We consider interventions with hypothetical CTL-inducing vaccines in a range of epidemiologically plausible pandemic scenarios. We estimate the achievable reduction in the attack rate, and, by adopting a model linking epidemic progression to the emergence of IAV variants, the opportunity for antigenic drift. We demonstrate that CTL-inducing vaccines have limited utility for modifying population-level outcomes if influenza-specific T cells found widely in adults already suppress transmission and prove difficult to enhance. Administration of CTL-inducing vaccines that are efficacious in "influenza-experienced" and "influenza-naive" hosts can likely slow transmission sufficiently to mitigate a moderate IAV pandemic. However if neutralising cross-reactive antibody to an emerging IAV are common in influenza-experienced hosts, as for the swine-variant H3N2v, boosting CTL immunity may be ineffective at reducing population spread, indicating that CTL-inducing vaccines are best used against novel subtypes such as H7N9. Unless vaccines cannot readily suppress transmission from infected hosts with naive T cell pools, targeting influenza-naive hosts is preferable. Such strategies are of enhanced benefit if naive hosts are typically intensively mixing children and when a subset of experienced hosts have pre-existing neutralising cross-reactive antibody. We show that CTL-inducing vaccination campaigns may have greater power to suppress antigenic drift than previously suggested, and targeting adults may be the optimal strategy to achieve this when the vaccination campaign does not have the power to curtail the attack rate. Our results highlight the need to design interventions based on pre-existing cellular immunity and knowledge of the host determinants of vaccine efficacy, and provide a framework for assessing the performance requirements of high-impact CTL-inducing vaccines.
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Affiliation(s)
- Kirsty J. Bolton
- School of Mathematical Sciences, University of Nottingham, Nottingham, United Kingdom
- School of Community Health Sciences, University of Nottingham, Nottingham, United Kingdom
- * E-mail:
| | - James M. McCaw
- Vaccine and Immunisation Research Group, Melbourne School of Population and Global Health, University of Melbourne, Melbourne, Australia
- Murdoch Childrens Research Institute, Melbourne, Australia
| | - Lorena Brown
- Department of Microbiology and Immunology, University of Melbourne, Melbourne, Australia
| | - David Jackson
- Department of Microbiology and Immunology, University of Melbourne, Melbourne, Australia
| | - Katherine Kedzierska
- Department of Microbiology and Immunology, University of Melbourne, Melbourne, Australia
| | - Jodie McVernon
- Vaccine and Immunisation Research Group, Melbourne School of Population and Global Health, University of Melbourne, Melbourne, Australia
- Murdoch Childrens Research Institute, Melbourne, Australia
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