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Lees JA, Russell TW, Shaw LP, Hellewell J. Recent approaches in computational modelling for controlling pathogen threats. Life Sci Alliance 2024; 7:e202402666. [PMID: 38906676 PMCID: PMC11192964 DOI: 10.26508/lsa.202402666] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2024] [Revised: 06/11/2024] [Accepted: 06/13/2024] [Indexed: 06/23/2024] Open
Abstract
In this review, we assess the status of computational modelling of pathogens. We focus on three disparate but interlinked research areas that produce models with very different spatial and temporal scope. First, we examine antimicrobial resistance (AMR). Many mechanisms of AMR are not well understood. As a result, it is hard to measure the current incidence of AMR, predict the future incidence, and design strategies to preserve existing antibiotic effectiveness. Next, we look at how to choose the finite number of bacterial strains that can be included in a vaccine. To do this, we need to understand what happens to vaccine and non-vaccine strains after vaccination programmes. Finally, we look at within-host modelling of antibody dynamics. The SARS-CoV-2 pandemic produced huge amounts of antibody data, prompting improvements in this area of modelling. We finish by discussing the challenges that persist in understanding these complex biological systems.
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Affiliation(s)
- John A Lees
- https://ror.org/02catss52 European Molecular Biology Laboratory, European Bioinformatics Institute, Wellcome Genome Campus, Hinxton, UK
| | - Timothy W Russell
- https://ror.org/00a0jsq62 Centre for Mathematical Modelling of Infectious Diseases, London School of Hygiene & Tropical Medicine, London, UK
| | - Liam P Shaw
- Department of Biology, University of Oxford, Oxford, UK
- Department of Biosciences, University of Durham, Durham, UK
| | - Joel Hellewell
- https://ror.org/02catss52 European Molecular Biology Laboratory, European Bioinformatics Institute, Wellcome Genome Campus, Hinxton, UK
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Reyburn R, Tuivaga E, Ratu F, Dunne E, Nand D, Kado J, Jenkins K, Tikoduadua L, Jenney A, Howden B, Ballard S, Fox K, Devi R, Satzke C, Rafai E, Kama M, Flasche S, Mulholland E, Russell F. The impact of 10-valent pneumococcal vaccine introduction on invasive disease in Fiji. THE LANCET REGIONAL HEALTH. WESTERN PACIFIC 2022; 20:100352. [PMID: 35028629 PMCID: PMC8741523 DOI: 10.1016/j.lanwpc.2021.100352] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
BACKGROUND In 2012, Fiji introduced the 10-valent pneumococcal conjugate vaccine (PCV10). We assessed the impact of PCV10 on invasive pneumococcal disease (IPD), probable bacterial or pneumococcal meningitis (PBPM), meningitis and sepsis 3-5 years post-introduction. METHODS Laboratory-confirmed IPD and PBPM cases were extracted from national laboratory records. ICD-10-AM coded all-cause meningitis and sepsis cases were extracted from national hospitalisation records. Incidence rate ratios were used to compare outcomes pre/post-PCV10, stratified by age groups: 1-23m, 2-4y, 5-9y, 10-19y, 20-54y, ≥55y. To account for different detection and serotyping methods in the pre-and post-PCV10 period, a Bayesian inference model estimated serotype-specific changes in IPD, using pneumococcal carriage and surveillance data. FINDINGS There were 423 IPD, 1,029 PBPM, 1,391 all-cause meningitis and 7,611 all-cause sepsis cases. Five years post-PCV10 introduction, IPD declined by 60% (95%CI: 37%, 76%) in children 1-23m months old, and in age groups 2-4y, 5-9y, 10-19y although confidence intervals spanned zero. PBPM declined by 36% (95%CI: 21%, 48%) among children 1-23 months old, and in all other age groups, although some confidence intervals spanned zero. Among children <5y of age, PCV10-type IPD declined by 83% (95%CI; 70%, 90%) and with no evidence of change in non-PCV10-type IPD (9%, 95%CI; -69, 43%). There was no change in all-cause meningitis or sepsis. Post-PCV10, the most common serotypes in vaccine age-eligible and non-age eligible people were serotypes 8 and 23B, and 3 and 7F, respectively. INTERPRETATIONS Our study demonstrates the effectiveness of PCV10 against IPD in a country in the Asia-Pacific of which there is a paucity of data. FUNDING This study was support by the Department of Foreign Affairs and Trade of the Australian Government and Fiji Health Sector Support Program (FHSSP). FHSSP is implemented by Abt JTA on behalf of the Australian Government.
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Affiliation(s)
- R. Reyburn
- Murdoch Children's Research Institute, Melbourne, Victoria, Australia
| | - E.J. Tuivaga
- The Ministry of Health and Medical Services, Suva, Fiji
| | - F.T. Ratu
- The Ministry of Health and Medical Services, Suva, Fiji
| | - E.M. Dunne
- Murdoch Children's Research Institute, Melbourne, Victoria, Australia
| | - D. Nand
- The Ministry of Health and Medical Services, Suva, Fiji
| | - J. Kado
- Fiji National University, Suva, Fiji
| | - K. Jenkins
- Australia's support to the Fiji health sector, Suva, Fiji
| | - L. Tikoduadua
- The Ministry of Health and Medical Services, Suva, Fiji
| | - A. Jenney
- Murdoch Children's Research Institute, Melbourne, Victoria, Australia
- Fiji National University, Suva, Fiji
- Department of Microbiology and Immunology, The University of Melbourne at the Peter Doherty Institute of Infection and Immunity, Melbourne, Victoria, Australia
| | - B.P. Howden
- Microbiological Diagnostic Unit Public Health Laboratory, The University of Melbourne at the Peter Doherty Institute of Infection and Immunity, Melbourne, Australia
- WHO Regional Reference Laboratory for Invasive Bacterial-Vaccine Preventable Diseases (IB-VPD) for Western Pacific Region, Microbiological Diagnostic Unit Public Health Laboratory, The University of Melbourne at the Peter Doherty Institute of Infection and Immunity, Melbourne, Australia
| | - S.A. Ballard
- Microbiological Diagnostic Unit Public Health Laboratory, The University of Melbourne at the Peter Doherty Institute of Infection and Immunity, Melbourne, Australia
- WHO Regional Reference Laboratory for Invasive Bacterial-Vaccine Preventable Diseases (IB-VPD) for Western Pacific Region, Microbiological Diagnostic Unit Public Health Laboratory, The University of Melbourne at the Peter Doherty Institute of Infection and Immunity, Melbourne, Australia
| | - K. Fox
- Regional Office for the Western Pacific, World Health Organization, Manila, Philippines
- Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - R. Devi
- The Ministry of Health and Medical Services, Suva, Fiji
| | - C. Satzke
- Murdoch Children's Research Institute, Melbourne, Victoria, Australia
- Department of Microbiology and Immunology, The University of Melbourne at the Peter Doherty Institute of Infection and Immunity, Melbourne, Victoria, Australia
- Department of Paediatrics, The University of Melbourne, Melbourne, Victoria, Australia
| | - E. Rafai
- The Ministry of Health and Medical Services, Suva, Fiji
| | - M. Kama
- The Ministry of Health and Medical Services, Suva, Fiji
| | - S. Flasche
- Centre for Mathematical Modelling for Infectious diseases, London School of Hygiene and Tropical Medicine, London, UK
| | - E.K. Mulholland
- Murdoch Children's Research Institute, Melbourne, Victoria, Australia
- Centre for Mathematical Modelling for Infectious diseases, London School of Hygiene and Tropical Medicine, London, UK
| | - F.M. Russell
- Murdoch Children's Research Institute, Melbourne, Victoria, Australia
- Centre for International Child Health, Department of Paediatrics, The University of Melbourne, Melbourne, Victoria, Australia
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Løchen A, Truscott JE, Croucher NJ. Analysing pneumococcal invasiveness using Bayesian models of pathogen progression rates. PLoS Comput Biol 2022; 18:e1009389. [PMID: 35176026 PMCID: PMC8901055 DOI: 10.1371/journal.pcbi.1009389] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Revised: 03/07/2022] [Accepted: 01/28/2022] [Indexed: 11/19/2022] Open
Abstract
The disease burden attributable to opportunistic pathogens depends on their prevalence in asymptomatic colonisation and the rate at which they progress to cause symptomatic disease. Increases in infections caused by commensals can result from the emergence of "hyperinvasive" strains. Such pathogens can be identified through quantifying progression rates using matched samples of typed microbes from disease cases and healthy carriers. This study describes Bayesian models for analysing such datasets, implemented in an RStan package (https://github.com/nickjcroucher/progressionEstimation). The models converged on stable fits that accurately reproduced observations from meta-analyses of Streptococcus pneumoniae datasets. The estimates of invasiveness, the progression rate from carriage to invasive disease, in cases per carrier per year correlated strongly with the dimensionless values from meta-analysis of odds ratios when sample sizes were large. At smaller sample sizes, the Bayesian models produced more informative estimates. This identified historically rare but high-risk S. pneumoniae serotypes that could be problematic following vaccine-associated disruption of the bacterial population. The package allows for hypothesis testing through model comparisons with Bayes factors. Application to datasets in which strain and serotype information were available for S. pneumoniae found significant evidence for within-strain and within-serotype variation in invasiveness. The heterogeneous geographical distribution of these genotypes is therefore likely to contribute to differences in the impact of vaccination in between locations. Hence genomic surveillance of opportunistic pathogens is crucial for quantifying the effectiveness of public health interventions, and enabling ongoing meta-analyses that can identify new, highly invasive variants.
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Affiliation(s)
- Alessandra Løchen
- Department of Infectious Disease Epidemiology, School of Public Health, St. Mary’s Campus, Imperial College London, London, United Kingdom
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, School of Public Health, White City Campus, Imperial College London, London, United Kingdom
| | - James E. Truscott
- Department of Infectious Disease Epidemiology, School of Public Health, St. Mary’s Campus, Imperial College London, London, United Kingdom
| | - Nicholas J. Croucher
- Department of Infectious Disease Epidemiology, School of Public Health, St. Mary’s Campus, Imperial College London, London, United Kingdom
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, School of Public Health, White City Campus, Imperial College London, London, United Kingdom
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4
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Rinta-Kokko H, Nurhonen M, Auranen K. Impact and effectiveness of a conjugate vaccine against invasive pneumococcal disease in Finland - a modelling approach. Hum Vaccin Immunother 2021; 17:1834-1843. [PMID: 33327857 PMCID: PMC8115766 DOI: 10.1080/21645515.2020.1836918] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The evaluation of the public health impact of a vaccination program is essential in monitoring its policy relevance. Vaccine impact (VI) is usually assessed in a before-after design, in which data on disease burden without vaccination program is required from a historical reference period. It takes into account the indirect effects and therefore aims to describe the public health performance of the vaccination program in the population. Vaccine effectiveness (VE), measured in parallel settings, quantifies the benefit for an individual of being vaccinated but does not address the indirect effects of a vaccination program. The motivation of this paper is to gain insight into patterns of how VI and VE have manifested under large-scale use of a ten-valent pneumococcal conjugate vaccine in Finnish children. We construct a simple pseudo-dynamic model that mimics typical post-vaccination trends in the incidences of pneumococcal carriage and invasive disease in children when the proportion of vaccine-type carriage decreases. In the context of the model, we define the parameters of interest for VI and VE and explore how their expected values evolve over time. For comparison, we demonstrate the application of VI and VE estimation by using register data.
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Affiliation(s)
- Hanna Rinta-Kokko
- Department of Public Health Solutions, Finnish Institute for Health and Welfare, Helsinki, Finland
| | - Markku Nurhonen
- Department of Public Health Solutions, Finnish Institute for Health and Welfare, Helsinki, Finland
| | - Kari Auranen
- Department of Mathematics and Statistics and Department of Clinical Medicine, University of Turku, Turku, Finland
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5
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Phillips MT, Warren JL, Givon-Lavi N, Tothpal A, Regev-Yochay G, Dagan R, Weinberger DM. Evaluating post-vaccine expansion patterns of pneumococcal serotypes. Vaccine 2020; 38:7756-7763. [PMID: 33164799 PMCID: PMC7664987 DOI: 10.1016/j.vaccine.2020.10.045] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Revised: 10/08/2020] [Accepted: 10/12/2020] [Indexed: 11/29/2022]
Abstract
BACKGROUND Streptococcus pneumoniae remains a leading cause of morbidity and mortality. Pneumococcal conjugate vaccines (PCVs) are effective but target only a fraction of the more than 90 pneumococcal serotypes. As a result, the introduction of PCVs has been followed by the emergence of non-vaccine serotypes. With higher-valency PCVs currently under development, there is a need to understand and predict patterns of serotype replacement to anticipate future changes. METHODS In this study, we fit a hierarchical Bayesian regression model to evaluate patterns of change in serotype prevalence post-PCV introduction in Israel from 2009 to 2016. RESULTS We found that the assumption that non-vaccine serotypes increase by the same proportion overestimates changes in serotype prevalence in Jewish and Bedouin children. Furthermore, pre-vaccine prevalence was positively associated with increases in prevalence over the study period. From our analyses, serotypes 12F, 8, 16F, 33F, 9N, 7B, 10A, 22F, 24F, and 17F were estimated to have gained the most cases of invasive pneumococcal disease through serotype replacement in the Jewish population. However, this model also failed to quantify some additional cases gained, suggesting that changes in carriage in children alone may be insufficient to explain serotype replacement in disease. CONCLUSIONS Understanding of serotype replacement is important as higher-valency vaccines are introduced.
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Affiliation(s)
- Maile T Phillips
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT, United States.
| | - Joshua L Warren
- Department of Biostatistics, Yale School of Public Health, New Haven, CT, United States
| | - Noga Givon-Lavi
- Faculty of Health Sciences, Ben-Gurion University of the Negev, Be'er Sheva, Israel
| | - Adrienn Tothpal
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT, United States; Semmelweis University, Institute of Medical Microbiology, Budapest, Hungary
| | - Gili Regev-Yochay
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel; Infection Prevention & Control Unit, Sheba Medical Center, Tel-Hashomer, Israel
| | - Ron Dagan
- Faculty of Health Sciences, Ben-Gurion University of the Negev, Be'er Sheva, Israel
| | - Daniel M Weinberger
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT, United States
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Colijn C, Corander J, Croucher NJ. Designing ecologically optimized pneumococcal vaccines using population genomics. Nat Microbiol 2020; 5:473-485. [PMID: 32015499 PMCID: PMC7614922 DOI: 10.1038/s41564-019-0651-y] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Accepted: 12/03/2019] [Indexed: 12/14/2022]
Abstract
Streptococcus pneumoniae (the pneumococcus) is a common nasopharyngeal commensal that can cause invasive pneumococcal disease (IPD). Each component of current protein-polysaccharide conjugate vaccines (PCVs) generally induces immunity specific to one of the approximately 100 pneumococcal serotypes, and typically eliminates it from carriage and IPD through herd immunity. Overall carriage rates remain stable owing to replacement by non-PCV serotypes. Consequently, the net change in IPD incidence is determined by the relative invasiveness of the pre- and post-PCV-carried pneumococcal populations. In the present study, we identified PCVs expected to minimize the post-vaccine IPD burden by applying Bayesian optimization to an ecological model of serotype replacement that integrated epidemiological and genomic data. We compared optimal formulations for reducing infant-only or population-wide IPD, and identified potential benefits to including non-conserved pneumococcal carrier proteins. Vaccines were also devised to minimize IPD resistant to antibiotic treatment, despite the ecological model assuming that resistance levels in the carried population would be preserved. We found that expanding infant-administered PCV valency is likely to result in diminishing returns, and that complementary pairs of infant- and adult-administered vaccines could be a superior strategy. PCV performance was highly dependent on the circulating pneumococcal population, further highlighting the advantages of a diversity of anti-pneumococcal vaccination strategies.
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Affiliation(s)
- Caroline Colijn
- Department of Mathematics, Simon Fraser University, Burnaby, BC, Canada.
- Department of Mathematics, Imperial College London, London, UK.
| | - Jukka Corander
- Department of Biostatistics, University of Oslo, Oslo, Norway
- Helsinki Institute of Information Technology, Department of Mathematics and Statistics, University of Helsinki, Helsinki, Finland
- Parasites & Microbes, Wellcome Sanger Institute, Wellcome Genome Campus, Cambridge, UK
| | - Nicholas J Croucher
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, London, UK
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Relationship Between Prevalence of Pneumococcal Serotypes and Their Neuraminidases in Carriers, Predictive Facts? ARCHIVES OF PEDIATRIC INFECTIOUS DISEASES 2020. [DOI: 10.5812/pedinfect.14100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Reid MC, Peebles K, Stansfield SE, Goodreau SM, Abernethy N, Gottlieb GS, Mittler JE, Herbeck JT. Models to predict the public health impact of vaccine resistance: A systematic review. Vaccine 2019; 37:4886-4895. [PMID: 31307874 DOI: 10.1016/j.vaccine.2019.07.013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Revised: 05/12/2019] [Accepted: 07/02/2019] [Indexed: 12/19/2022]
Abstract
Pathogen evolution is a potential threat to the long-term benefits provided by public health vaccination campaigns. Mathematical modeling can be a powerful tool to examine the forces responsible for the development of vaccine resistance and to predict its public health implications. We conducted a systematic review of existing literature to understand the construction and application of vaccine resistance models. We identified 26 studies that modeled the public health impact of vaccine resistance for 12 different pathogens. Most models predicted that vaccines would reduce overall disease burden in spite of evolution of vaccine resistance. Relatively few pathogens and populations for which vaccine resistance may be problematic were covered in the reviewed studies, with low- and middle-income countries particularly under-represented. We discuss the key components of model design, as well as patterns of model predictions.
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Affiliation(s)
- Molly C Reid
- Department of Epidemiology, 1959 NE Pacific Street, Magnuson Health Sciences Center, Room F-262, Seattle, WA 98195, United States; International Clinical Research Center, Department of Global Health, 908 Jefferson St., Seattle, WA 98104, United States.
| | - Kathryn Peebles
- Department of Epidemiology, 1959 NE Pacific Street, Magnuson Health Sciences Center, Room F-262, Seattle, WA 98195, United States; International Clinical Research Center, Department of Global Health, 908 Jefferson St., Seattle, WA 98104, United States.
| | - Sarah E Stansfield
- Department of Epidemiology, 1959 NE Pacific Street, Magnuson Health Sciences Center, Room F-262, Seattle, WA 98195, United States; Department of Anthropologym Denny Hall, University of Washington, Seattle, WA 98195, United States.
| | - Steven M Goodreau
- Department of Epidemiology, 1959 NE Pacific Street, Magnuson Health Sciences Center, Room F-262, Seattle, WA 98195, United States; Department of Anthropologym Denny Hall, University of Washington, Seattle, WA 98195, United States.
| | - Neil Abernethy
- Department of Biomedical Informatics and Medical Education, University of Washington, Box 358047, Seattle, WA 98195, United States; Department of Health Services, 1959 NE Pacific St, Magnuson Health Sciences Center, Room H-680, Seattle, WA 98195-7660, United States.
| | - Geoffrey S Gottlieb
- Division of Allergy and Infectious Diseases & Center for Emerging & Re-Emerging Infectious Diseases, Department of Medicine & Department of Global Health, 750 Republican St., Building E, Seattle, WA 98109, United States.
| | - John E Mittler
- Department of Microbiology, 750 Republican St., Building F, Seattle, WA 98109, United States.
| | - Joshua T Herbeck
- International Clinical Research Center, Department of Global Health, 908 Jefferson St., Seattle, WA 98104, United States.
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Croucher NJ, Løchen A, Bentley SD. Pneumococcal Vaccines: Host Interactions, Population Dynamics, and Design Principles. Annu Rev Microbiol 2018; 72:521-549. [DOI: 10.1146/annurev-micro-090817-062338] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Streptococcus pneumoniae (the pneumococcus) is a nasopharyngeal commensal and respiratory pathogen. Most isolates express a capsule, the species-wide diversity of which has been immunologically classified into ∼100 serotypes. Capsule polysaccharides have been combined into multivalent vaccines widely used in adults, but the T cell independence of the antibody response means they are not protective in infants. Polysaccharide conjugate vaccines (PCVs) trigger a T cell–dependent response through attaching a carrier protein to capsular polysaccharides. The immune response stimulated by PCVs in infants inhibits carriage of vaccine serotypes (VTs), resulting in population-wide herd immunity. These were replaced in carriage by non-VTs. Nevertheless, PCVs drove reductions in infant pneumococcal disease, due to the lower mean invasiveness of the postvaccination bacterial population; age-varying serotype invasiveness resulted in a smaller reduction in adult disease. Alternative vaccines being tested in trials are designed to provide species-wide protection through stimulating innate and cellular immune responses, alongside antibodies to conserved antigens.
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Affiliation(s)
- Nicholas J. Croucher
- Department of Infectious Disease Epidemiology, Imperial College London, London W2 1PG, United Kingdom
| | - Alessandra Løchen
- Department of Infectious Disease Epidemiology, Imperial College London, London W2 1PG, United Kingdom
| | - Stephen D. Bentley
- Infection Genomics Programme, Wellcome Sanger Institute, Hinxton, Cambridge CB10 1SA, United Kingdom
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Masala GL, Lipsitch M, Bottomley C, Flasche S. Exploring the role of competition induced by non-vaccine serotypes for herd protection following pneumococcal vaccination. J R Soc Interface 2018; 14:rsif.2017.0620. [PMID: 29093131 PMCID: PMC5721164 DOI: 10.1098/rsif.2017.0620] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Accepted: 10/11/2017] [Indexed: 02/02/2023] Open
Abstract
The competitive pressure from non-vaccine serotypes may have helped pneumococcal conjugate vaccines (PCVs) to limit vaccine-type (VT) serotype prevalence. We aimed to investigate if, consequently, the indirect protection of vaccines targeting most pneumococcal serotypes could fall short of the profound effects of current formulations. We compared three previously described pneumococcal models harmonized to simulate 20 serotypes with a combined pre-vaccination prevalence in children younger than 5-years-old of 40%. We simulated vaccines of increasing valency by adding serotypes in order of their competitiveness and explored their ability to reduce VT carriage by 95% within 10 years after introduction. All models predicted that additional valency will reduce indirect vaccine effects and hence the overall vaccine impact on carriage both in children and adults. Consequently, the minimal effective coverage (efficacy against carriage×vaccine coverage) needed to eliminate VT carriage increased with increasing valency. One model predicted this effect to be modest, while the other two predicted that high-valency vaccines may struggle to eliminate VT pneumococci unless vaccine efficacy against carriage can be substantially improved. Similar results were obtained when settings of higher transmission intensity and different PCV formulations were explored. Failure to eliminate carriage as a result of increased valency could lead to overall decreased impact of vaccination if the disease burden caused by the added serotypes is low. Hence, a comparison of vaccine formulations of varying valency, and pan-valent formulations in particular, should consider the invasiveness of targeted serotypes, as well as efficacy against carriage.
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Affiliation(s)
- G L Masala
- Centre for Mathematical Modelling and Infectious Diseases, Department of Infectious disease Epidemiology, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK.,School of Computing, Electronics and Mathematics, University of Plymouth, Plymouth, UK
| | - M Lipsitch
- Center for Communicable Disease Dynamics, Department of Epidemiology, Harvard T. H. Chan School of Public Health, Boston, Massachusetts
| | - C Bottomley
- Centre for Mathematical Modelling and Infectious Diseases, Department of Infectious disease Epidemiology, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK
| | - S Flasche
- Centre for Mathematical Modelling and Infectious Diseases, Department of Infectious disease Epidemiology, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK
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Pneumococcal Phenotype and Interaction with Nontypeable Haemophilus influenzae as Determinants of Otitis Media Progression. Infect Immun 2018; 86:IAI.00727-17. [PMID: 29378791 DOI: 10.1128/iai.00727-17] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Accepted: 01/19/2018] [Indexed: 02/03/2023] Open
Abstract
All-cause otitis media (OM) incidence has declined in numerous settings following introduction of pneumococcal conjugate vaccines (PCVs) despite increases in carriage of nonvaccine pneumococcal serotypes escaping immune pressure. To understand the basis for the declining incidence, we assessed the intrinsic capacity of pneumococcal serotypes to cause OM independently and in polymicrobial infections involving nontypeable Haemophilus influenzae (NTHi) using samples obtained from middle ear fluid and nasopharyngeal cultures before PCV7/13 rollout. Data included samples from OM episodes (11,811) submitted for cultures during a 10-year prospective study in southern Israel and nasopharyngeal samples (1,588) from unvaccinated asymptomatic children in the same population. We compared data representing pneumococcal serotype diversity across carriage and disease isolates with and without NTHi coisolation. We also measured associations between the pneumococcal phenotype and the rate of progression from colonization to OM in the presence and absence of NTHi. Whereas pneumococcal serotype diversity was lower in single-species OM than in single-species colonization, levels of serotype diversity did not differ significantly between colonization and OM in mixed-species episodes. Serotypes differed roughly 100-fold in progression rates, and those differences were attenuated in polymicrobial episodes. Vaccine serotype pneumococci had higher rates of progression than nonvaccine serotypes. While serotype invasiveness was a weak predictor of the OM progression rate, efficient capsular metabolic properties-traditionally thought to serve as an advantage in colonization-predicted an enhanced rate of progression to complex OM. The lower capacity of nonvaccine serotypes to cause OM may partially account for reductions in all-cause OM incidence despite serotype replacement in carriage following rollout of PCVs.
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Flasche S, Ojal J, Le Polain de Waroux O, Otiende M, O'Brien KL, Kiti M, Nokes DJ, Edmunds WJ, Scott JAG. Assessing the efficiency of catch-up campaigns for the introduction of pneumococcal conjugate vaccine: a modelling study based on data from PCV10 introduction in Kilifi, Kenya. BMC Med 2017; 15:113. [PMID: 28592303 PMCID: PMC5463405 DOI: 10.1186/s12916-017-0882-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Accepted: 05/22/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The World Health Organisation recommends the use of catch-up campaigns as part of the introduction of pneumococcal conjugate vaccines (PCVs) to accelerate herd protection and hence PCV impact. The value of a catch-up campaign is a trade-off between the costs of vaccinating additional age groups and the benefit of additional direct and indirect protection. There is a paucity of observational data, particularly from low- and middle-income countries, to quantify the optimal breadth of such catch-up campaigns. METHODS In Kilifi, Kenya, PCV10 was introduced in 2011 using the three-dose Expanded Programme on Immunisation infant schedule and a catch-up campaign in children <5 years old. We fitted a transmission dynamic model to detailed local data, including nasopharyngeal carriage and invasive pneumococcal disease (IPD), to infer the marginal impact of the PCV catch-up campaign over hypothetical routine cohort vaccination in that setting and to estimate the likely impact of alternative campaigns and their dose efficiency. RESULTS We estimated that, within 10 years of introduction, the catch-up campaign among children <5 years old prevents an additional 65 (48-84) IPD cases across age groups, compared to PCV cohort introduction alone. Vaccination without any catch-up campaign prevented 155 (121-193) IPD cases and used 1321 (1058-1698) PCV doses per IPD case prevented. In the years after implementation, the PCV programme gradually accrues herd protection, and hence its dose efficiency increases: 10 years after the start of cohort vaccination alone the programme used 910 (732-1184) doses per IPD case averted. We estimated that a two-dose catch-up among children <1 year old uses an additional 910 (732-1184) doses per additional IPD case averted. Furthermore, by extending a single-dose catch-up campaign to children aged 1 to <2 years and subsequently to those aged 2 to <5 years, the campaign uses an additional 412 (296-606) and 543 (403-763) doses per additional IPD case averted. These results were not sensitive to vaccine coverage, serotype competition, the duration of vaccine protection or the relative protection of infants. CONCLUSIONS We find that catch-up campaigns are a highly dose-efficient way to accelerate population protection against pneumococcal disease.
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Affiliation(s)
- Stefan Flasche
- Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, Keppel Street, WC1E 7HT, London, UK.
| | - John Ojal
- Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, Keppel Street, WC1E 7HT, London, UK
- Kenya Medical Research Institute (KEMRI)-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya
| | - Olivier Le Polain de Waroux
- Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, Keppel Street, WC1E 7HT, London, UK
| | - Mark Otiende
- Kenya Medical Research Institute (KEMRI)-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya
| | - Katherine L O'Brien
- International Vaccine Access Center, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Moses Kiti
- Kenya Medical Research Institute (KEMRI)-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya
| | - D James Nokes
- Kenya Medical Research Institute (KEMRI)-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya
- University of Warwick and WIDER, Coventry, UK
| | - W John Edmunds
- Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, Keppel Street, WC1E 7HT, London, UK
| | - J Anthony G Scott
- Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, Keppel Street, WC1E 7HT, London, UK
- Kenya Medical Research Institute (KEMRI)-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya
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Wang Y, Jiang B, Guo Y, Li W, Tian Y, Sonnenberg GF, Weiser JN, Ni X, Shen H. Cross-protective mucosal immunity mediated by memory Th17 cells against Streptococcus pneumoniae lung infection. Mucosal Immunol 2017; 10:250-259. [PMID: 27118490 PMCID: PMC5083242 DOI: 10.1038/mi.2016.41] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Accepted: 03/22/2016] [Indexed: 02/04/2023]
Abstract
Pneumonia caused by Streptococcus pneumoniae (Sp) remains a leading cause of serious illness and death worldwide. Immunization with conjugated pneumococcal vaccine has lowered the colonization rate and consequently invasive diseases by inducing serotype-specific antibodies. However, many of the current pneumonia cases result from infection by serotype strains not included in the vaccine. In this study, we asked if cross-protection against lung infection by heterologous strains can be induced, and investigated the underlying immune mechanism. We found that immune mice recovered from a prior infection were protected against heterologous Sp strains in the pneumonia challenge model, as evident by accelerated bacterial clearance, reduced pathology, and apoptosis of lung epithelial cells. Sp infection in the lung induced strong T-helper type 17 (Th17) responses at the lung mucosal site. Transfer of CD4+ T cells from immune mice provided heterologous protection against pneumonia, and this protection was abrogated by interleukin-17A (IL-17A) blockade. Transfer of memory CD4+ T cells from IL-17A-knockout mice failed to provide protection. These results indicate that memory Th17 cells had a key role in providing protection against pneumonia in a serotype-independent manner and suggest the feasibility of developing a broadly protective vaccine against bacterial pneumonia by targeting mucosal Th17 T cells.
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Affiliation(s)
- Yan Wang
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, PA 19104, USA
| | - Bin Jiang
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, PA 19104, USA
| | - Yongli Guo
- Beijing Pediatric Research Institute, Beijing Children’s Hospital, Capital Medical University, Beijing 100045, China
| | - Wenchao Li
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, PA 19104, USA
| | - Ying Tian
- Department of Pharmacology, Center for Translational Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Gregory F Sonnenberg
- Joan and Sanford I. Weill Department of Medicine, Division of Gastroenterology and Hepatology, Department of Microbiology & Immunology, and The Jill Robert’s Institute for Research in Inflammatory Bowel Disease, Weill Cornell Medical College, New York, NY, USA
| | - Jeffery N. Weiser
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, PA 19104, USA
,Department of Microbiology, NYU School of Medicine, New York, NY 10016, USA
| | - Xin Ni
- Beijing Pediatric Research Institute, Beijing Children’s Hospital, Capital Medical University, Beijing 100045, China
| | - Hao Shen
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, PA 19104, USA
,Beijing Pediatric Research Institute, Beijing Children’s Hospital, Capital Medical University, Beijing 100045, China
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Hausdorff WP, Hanage WP. Interim results of an ecological experiment - Conjugate vaccination against the pneumococcus and serotype replacement. Hum Vaccin Immunother 2016; 12:358-74. [PMID: 26905681 PMCID: PMC5049718 DOI: 10.1080/21645515.2015.1118593] [Citation(s) in RCA: 84] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Streptococcus pneumoniae has more than 95 serotypes, each of which presumably can cause sepsis, meningitis, pneumonia, and acute otitis media. Pneumococcal conjugate vaccines (PCV) targeted against a limited number of serotypes have nonetheless revealed an impressive impact on each manifestation of pneumococcal disease. At the same time, growing evidence of significant non-vaccine type (NVT) replacement disease following implementation of infant PCV programs has raised questions about the long-term viability of PCV immunization strategies and how to optimize PCV formulations. We discuss here theoretical and practical considerations regarding serotype replacement, and provide a snapshot of the most important NVT types seen to date after implementation of the 2 higher-valent PCVs.
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Affiliation(s)
| | - William P Hanage
- b Department of Epidemiology ; Center for Communicable Disease Dynamics; Harvard TH Chan School of Public Health ; Boston , MA , USA
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Weinberger DM, Grant LR, Weatherholtz RC, Warren JL, O'Brien KL, Hammitt LL. Relating Pneumococcal Carriage Among Children to Disease Rates Among Adults Before and After the Introduction of Conjugate Vaccines. Am J Epidemiol 2016; 183:1055-62. [PMID: 27188949 DOI: 10.1093/aje/kwv283] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2015] [Accepted: 10/13/2015] [Indexed: 11/12/2022] Open
Abstract
The use of pneumococcal conjugate vaccines (PCVs) in children has a strong indirect effect on disease rates in adults. When children are vaccinated with PCVs, other serotypes that are not targeted by the vaccine can increase in frequency (serotype replacement) and reduce the direct and indirect benefits of the vaccine. To understand and predict the likely impacts of serotype replacement, it is important to know how patterns in the transmission of serotypes among children relate to disease rates in adults. We used data on pneumococcal carriage and disease from Navajo Nation children and adults collected before and after the routine use of PCVs (1998-2012). Using regression models within a Bayesian framework, we found that serotype-specific carriage and invasiveness (disease incidence divided by carriage prevalence) had similar patterns in children and adults. Moreover, carriage in children, invasiveness in children, and a serotype-specific random intercept (which captured additional variation associated with the serotypes) could predict the incidence serotype-specific pneumococcal disease in adults 18-39 years of age and those 40 years of age or older in the era of routine use of PCVs. These models could help us predict the effects of future pneumococcal vaccine use in children on disease rates in adults, and the modeling approach developed here could be used to test these findings in other settings.
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Pichichero ME, Khan MN, Xu Q. Next generation protein based Streptococcus pneumoniae vaccines. Hum Vaccin Immunother 2016; 12:194-205. [PMID: 26539741 PMCID: PMC4962723 DOI: 10.1080/21645515.2015.1052198] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Revised: 04/27/2015] [Accepted: 05/12/2015] [Indexed: 12/22/2022] Open
Abstract
All currently available Streptococcus pneumoniae (Spn) vaccines have limitations due to their capsular serotype composition. Both the 23-valent Spn polysaccharide vaccine (PPV) and 7, 10, or 13-valent Spn conjugate vaccines (PCV-7, 10, -13) are serotype-based vaccines and therefore they elicit only serotype-specific immunity. Emergence of replacement Spn strains expressing other serotypes has consistently occurred following introduction of capsular serotype based Spn vaccines. Furthermore, capsular polysaccharide vaccines are less effective in protection against non-bacteremic pneumonia and acute otitis media (AOM) than against invasive pneumococcal disease (IPD). These shortcomings of capsular polysaccharide-based Spn vaccines have created high interest in development of non-serotype specific protein-based vaccines that could be effective in preventing both IPD and non-IPD infections. This review discusses the progress to date on development of Spn protein vaccine candidates that are highly conserved by all Spn strains, are highly conserved, exhibit maximal antigenicity and minimal reactogenicity to replace or complement the current capsule-based vaccines. Key to development of a protein based Spn vaccine is an understanding of Spn pathogenesis. Based on pathogenesis, a protein-based Spn vaccine should include one or more ingredients that reduce NP colonization below a pathogenic inoculum. Elimination of all Spn colonization may not be achievable or even advisable. The level of expression of a target protein antigen during pathogenesis is another key to the success of protein based vaccines.. As with virtually all currently licensed vaccines, production of a serum antibody response in response to protein based vaccines is anticipated to provide protection from Spn infections. A significant advantage that protein vaccine formulations can offer over capsule based vaccination is their potential benefits associated with natural priming and boosting to all strains of Spn. One of the most universal and comprehensive approaches of identifying novel vaccine candidates is the investigation of human sera from different disease stages of natural infections. Antigens that are robustly reactive in preliminary human serum screening constitute a pathogen-specific antigenome. This strategy has identified a number of Spn protein vaccine candidates that are moving forward in human clinical trials.
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Affiliation(s)
| | - M Nadeem Khan
- Research Institute; Rochester General Hospital; Rochester, NY USA
| | - Qingfu Xu
- Research Institute; Rochester General Hospital; Rochester, NY USA
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Satzke C, Dunne EM, Porter BD, Klugman KP, Mulholland EK. The PneuCarriage Project: A Multi-Centre Comparative Study to Identify the Best Serotyping Methods for Examining Pneumococcal Carriage in Vaccine Evaluation Studies. PLoS Med 2015; 12:e1001903; discussion e1001903. [PMID: 26575033 PMCID: PMC4648509 DOI: 10.1371/journal.pmed.1001903] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Accepted: 10/09/2015] [Indexed: 01/17/2023] Open
Abstract
BACKGROUND The pneumococcus is a diverse pathogen whose primary niche is the nasopharynx. Over 90 different serotypes exist, and nasopharyngeal carriage of multiple serotypes is common. Understanding pneumococcal carriage is essential for evaluating the impact of pneumococcal vaccines. Traditional serotyping methods are cumbersome and insufficient for detecting multiple serotype carriage, and there are few data comparing the new methods that have been developed over the past decade. We established the PneuCarriage project, a large, international multi-centre study dedicated to the identification of the best pneumococcal serotyping methods for carriage studies. METHODS AND FINDINGS Reference sample sets were distributed to 15 research groups for blinded testing. Twenty pneumococcal serotyping methods were used to test 81 laboratory-prepared (spiked) samples. The five top-performing methods were used to test 260 nasopharyngeal (field) samples collected from children in six high-burden countries. Sensitivity and positive predictive value (PPV) were determined for the test methods and the reference method (traditional serotyping of >100 colonies from each sample). For the alternate serotyping methods, the overall sensitivity ranged from 1% to 99% (reference method 98%), and PPV from 8% to 100% (reference method 100%), when testing the spiked samples. Fifteen methods had ≥70% sensitivity to detect the dominant (major) serotype, whilst only eight methods had ≥70% sensitivity to detect minor serotypes. For the field samples, the overall sensitivity ranged from 74.2% to 95.8% (reference method 93.8%), and PPV from 82.2% to 96.4% (reference method 99.6%). The microarray had the highest sensitivity (95.8%) and high PPV (93.7%). The major limitation of this study is that not all of the available alternative serotyping methods were included. CONCLUSIONS Most methods were able to detect the dominant serotype in a sample, but many performed poorly in detecting the minor serotype populations. Microarray with a culture amplification step was the top-performing method. Results from this comprehensive evaluation will inform future vaccine evaluation and impact studies, particularly in low-income settings, where pneumococcal disease burden remains high.
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Affiliation(s)
- Catherine Satzke
- Pneumococcal Research Group, Murdoch Childrens Research Institute, Royal Children’s Hospital, Parkville, Victoria, Australia
- Department of Microbiology and Immunology, University of Melbourne, Peter Doherty Institute for Infection and Immunity, Parkville, Victoria, Australia
- * E-mail:
| | - Eileen M. Dunne
- Pneumococcal Research Group, Murdoch Childrens Research Institute, Royal Children’s Hospital, Parkville, Victoria, Australia
| | - Barbara D. Porter
- Pneumococcal Research Group, Murdoch Childrens Research Institute, Royal Children’s Hospital, Parkville, Victoria, Australia
| | - Keith P. Klugman
- Hubert Department of Global Health, Rollins School of Public Health, Emory University, Atlanta, Georgia, United States of America
| | - E. Kim Mulholland
- Pneumococcal Research Group, Murdoch Childrens Research Institute, Royal Children’s Hospital, Parkville, Victoria, Australia
- Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, United Kingdom
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The serotype distribution among healthy carriers before vaccination is essential for predicting the impact of pneumococcal conjugate vaccine on invasive disease. PLoS Comput Biol 2015; 11:e1004173. [PMID: 25879748 PMCID: PMC4400047 DOI: 10.1371/journal.pcbi.1004173] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2014] [Accepted: 02/05/2015] [Indexed: 11/24/2022] Open
Abstract
Pneumococcal conjugate vaccines (PCVs) have substantially reduced morbidity and mortality of pneumococcal disease. The impact of the 7-valent PCV on all-serotype invasive pneumococcal disease (IPD) among children was reported to vary between high-income countries. We investigate the ability to predict this heterogeneity from pre-vaccination data. We propose a parsimonious model that predicts the impact of PCVs from the odds of vaccine serotype (VT) among carriers and IPD cases in the pre-PCV period, assuming that VT are eliminated in a mature PCV programme, that full serotype replacement occurs in carriage and that invasiveness of the NVT group is unchanged. We test model performance against the reported impact of PCV7 on childhood IPD in high-income countries from a recent meta-analysis. The odds of pre-PCV7 VT IPD, PCV schedule, PCV coverage and whether a catch up campaign was used for introduction was gathered from the same analysis. We conducted a literature review and meta-analysis to obtain the odds of pre-PCV7 VT carriage in the respective settings. The model predicted the reported impact on childhood IPD of mature PCV programmes; the ratio of predicted and observed incidence risk ratios was close to 1 in all settings. In the high income settings studied differences in schedule, coverage, and catch up campaigns were not associated with the observed heterogeneity in impact of PCV7 on childhood all-serotype IPD. The pre-PCV7 proportion of VT IPD alone also had limited predictive value. The pre-PCV7 proportion of VT carriage and IPD are the main determinants for the impact of PCV7 on childhood IPD and can be combined in a simple model to provide predictions of the vaccine preventable burden of IPD. Pneumococcal vaccines (PCVs) that protect children against 7, 10 and 13 of the most pathogenic pneumococcal serotypes have substantially reduced childhood morbidity and mortality. A recent analysis that evaluated the impact of the 7 valent PCV in multiple high income settings in North America, Europe and Oceania found that the magnitude of all-serotype invasive pneumococcal disease reduction varied greatly between settings (24%-83%). We explored potential sources for that variation, including differences in disease epidemiology before vaccination, vaccine coverage, vaccine schedules and the use of catch-up campaigns for introduction. We find that differences in reported disease impact among mature PCV programmes are likely to be unrelated to the differences in the vaccine programme but can be predicted from a simple model based on pre-vaccination epidemiology, in particular the proportion of vaccine serotypes detected among patients with invasive pneumococcal disease and the proportion of vaccine serotypes that are found in the nasopharynx of healthy individuals. This model presents a useful tool to estimate the potential impact of PCVs (as a relative rate reduction), highlights the essential role of pre-vaccination carriage in healthy individuals for disease impact of PCVs and can estimate the prevented burden of disease where disease surveillance is unavailable.
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Abstract
Gram-positive organisms, including the pathogens Staphylococcus aureus, Streptococcus pneumoniae, and Enterococcus faecalis, have dynamic cell envelopes that mediate interactions with the environment and serve as the first line of defense against toxic molecules. Major components of the cell envelope include peptidoglycan (PG), which is a well-established target for antibiotics, teichoic acids (TAs), capsular polysaccharides (CPS), surface proteins, and phospholipids. These components can undergo modification to promote pathogenesis, decrease susceptibility to antibiotics and host immune defenses, and enhance survival in hostile environments. This chapter will cover the structure, biosynthesis, and important functions of major cell envelope components in gram-positive bacteria. Possible targets for new antimicrobials will be noted.
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Hausdorff WP, Hoet B, Adegbola RA. Predicting the impact of new pneumococcal conjugate vaccines: serotype composition is not enough. Expert Rev Vaccines 2014; 14:413-28. [PMID: 25266168 DOI: 10.1586/14760584.2015.965160] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Streptococcus pneumoniae is a major cause of childhood morbidity and mortality worldwide. A heptavalent polysaccharide-protein conjugate vaccine (PCV) has proven highly effective in preventing pneumococcal disease in industrialized countries. Two higher-valent pneumococcal conjugate vaccines are now widely available, even in the poorest countries. These differ from each other in the number of serotypes and carrier proteins used for their conjugation. Some have assumed that the only meaningful clinical difference between PCV formulations is a function of the number of serotypes each contains. A careful review of recent clinical data with these and several unlicensed PCV formulations points to important similarities but also that some key properties of each vaccine likely differ from one another.
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