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Thao Le TM, Madec S, Gjini E. Disentangling how multiple traits drive 2 strain frequencies in SIS dynamics with coinfection. J Theor Biol 2022; 538:111041. [DOI: 10.1016/j.jtbi.2022.111041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Revised: 12/01/2021] [Accepted: 01/18/2022] [Indexed: 10/19/2022]
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2
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Løchen A, Anderson RM. Dynamic transmission models and economic evaluations of pneumococcal conjugate vaccines: a quality appraisal and limitations. Clin Microbiol Infect 2021. [DOI: 10.1016/j.cmi.2021.07.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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3
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Løchen A, Anderson R. Dynamic transmission models and economic evaluations of pneumococcal conjugate vaccines: a quality appraisal and limitations. Clin Microbiol Infect 2020; 26:60-70. [DOI: 10.1016/j.cmi.2019.04.026] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Revised: 04/08/2019] [Accepted: 04/22/2019] [Indexed: 02/01/2023]
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4
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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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5
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Watkins ER, Maiden MC, Gupta S. Metabolic competition as a driver of bacterial population structure. Future Microbiol 2016; 11:1339-1357. [PMID: 27660887 DOI: 10.2217/fmb-2016-0079] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Understanding the processes whereby diversity arises and is maintained in pathogen populations is pivotal for designing disease control interventions. A particular problem is the maintenance of strain structure in bacterial pathogen populations despite frequent genetic exchange. Although several theoretical frameworks have been put forward to explain this widespread phenomenon, few have focused on the role of genes encoding metabolic functions, despite an increasing recognition of their importance in pathogenesis and transmission. In this article, we review the literature for evidence of metabolic niches within the host and discuss theoretical frameworks which examine ecological interactions between metabolic genes. We contend that metabolic competition is an important phenomenon which contributes to the maintenance of population structure and diversity of many bacterial pathogens.
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Affiliation(s)
- Eleanor R Watkins
- Department of Zoology, University of Oxford, South Parks Road, Oxford, OX1 3PS, UK
| | - Martin Cj Maiden
- Department of Zoology, University of Oxford, South Parks Road, Oxford, OX1 3PS, UK
| | - Sunetra Gupta
- Department of Zoology, University of Oxford, South Parks Road, Oxford, OX1 3PS, UK
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6
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Periodic solutions in an SIRWS model with immune boosting and cross-immunity. J Theor Biol 2016; 410:55-64. [PMID: 27575466 DOI: 10.1016/j.jtbi.2016.08.034] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Revised: 08/17/2016] [Accepted: 08/26/2016] [Indexed: 11/20/2022]
Abstract
Incidence of whooping cough, an infection caused by Bordetella pertussis and Bordetella parapertussis, has been on the rise since the 1980s in many countries. Immunological interactions, such as immune boosting and cross-immunity between pathogens, have been hypothesised to be important drivers of epidemiological dynamics. We present a two-pathogen model of transmission which examines how immune boosting and cross-immunity can influence the timing and severity of epidemics. We use a combination of numerical simulations and bifurcation techniques to study the dynamical properties of the system, particularly the conditions under which stable periodic solutions are present. We derive analytic expressions for the steady state of the single-pathogen model, and give a condition for the presence of periodic solutions. A key result from our two-pathogen model is that, while studies have shown that immune boosting at relatively strong levels can independently generate periodic solutions, cross-immunity allows for the presence of periodic solutions even when the level of immune boosting is weak. Asymmetric cross-immunity can produce striking increases in the incidence and period. Our study underscores the importance of developing a better understanding of the immunological interactions between pathogens in order to improve model-based interpretations of epidemiological data.
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Gjini E, Valente C, Sá-Leão R, Gomes MGM. How direct competition shapes coexistence and vaccine effects in multi-strain pathogen systems. J Theor Biol 2015; 388:50-60. [PMID: 26471070 DOI: 10.1016/j.jtbi.2015.09.031] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Revised: 09/02/2015] [Accepted: 09/22/2015] [Indexed: 11/25/2022]
Abstract
We describe an integrated modeling framework for understanding strain coexistence in polymorphic pathogen systems. Previous studies have debated the utility of neutral formulations and focused on cross-immunity between strains as a major stabilizing mechanism. Here we convey that direct competition for colonization mediates stable coexistence only when competitive abilities amongst pathogen clones satisfy certain pairwise asymmetries. We illustrate our ideas with nested SIS models of single and dual colonization, applied to polymorphic pneumococcal bacteria. By fitting the models to cross-sectional prevalence data from Portugal (before and after the introduction of a seven-valent pneumococcal conjugate vaccine), we are able to not only statistically compare neutral and non-neutral epidemiological formulations, but also estimate vaccine efficacy, transmission and competition parameters simultaneously. Our study highlights that the response of polymorphic pathogen populations to interventions holds crucial information about strain interactions, which can be extracted by suitable nested modeling.
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Affiliation(s)
- Erida Gjini
- Instituto Gulbenkian de Ciência, Apartado 14, 2781-901 Oeiras, Portugal.
| | - Carina Valente
- Laboratory of Molecular Microbiology of Human Pathogens, Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Raquel Sá-Leão
- Laboratory of Molecular Microbiology of Human Pathogens, Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
| | - M Gabriela M Gomes
- CIBIO-InBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, Universidade de Porto, Portugal; Instituto de Matemática e Estatística, Universidade de São Paulo, Brazil; Liverpool School of Tropical Medicine, Liverpool, United Kingdom
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de Cellès MD, Pons-Salort M, Varon E, Vibet MA, Ligier C, Letort V, Opatowski L, Guillemot D. Interaction of Vaccination and Reduction of Antibiotic Use Drives Unexpected Increase of Pneumococcal Meningitis. Sci Rep 2015; 5:11293. [PMID: 26063589 PMCID: PMC4462765 DOI: 10.1038/srep11293] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2014] [Accepted: 05/11/2015] [Indexed: 01/18/2023] Open
Abstract
Antibiotic-use policies may affect pneumococcal conjugate-vaccine effectiveness. The reported increase of pneumococcal meningitis from 2001 to 2009 in France, where a national campaign to reduce antibiotic use was implemented in parallel to the introduction of the 7-valent conjugate vaccine, provides unique data to assess these effects. We constructed a mechanistic pneumococcal transmission model and used likelihood to assess the ability of competing hypotheses to explain that increase. We find that a model integrating a fitness cost of penicillin resistance successfully explains the overall and age-stratified pattern of serotype replacement. By simulating counterfactual scenarios of public health interventions in France, we propose that this fitness cost caused a gradual and pernicious interaction between the two interventions by increasing the spread of nonvaccine, penicillin-susceptible strains. More generally, our results indicate that reductions of antibiotic use may counteract the benefits of conjugate vaccines introduced into countries with low vaccine-serotype coverages and high-resistance frequencies. Our findings highlight the key role of antibiotic use in vaccine-induced serotype replacement and suggest the need for more integrated approaches to control pneumococcal infections.
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Affiliation(s)
- Matthieu Domenech de Cellès
- Institut Pasteur, Unité de Pharmaco-Épidémiologie et Maladies Infectieuses, F–75015 Paris, France
- INSERM, U1181, F–75015 Paris, France
- Univ. Pierre et Marie Curie, Cellule Pasteur UPMC, F–75005 Paris, France
- Univ. Versailles Saint Quentin, UFR des Sciences de la Santé Simone-Veil, EA 4499, F–78180 Montigny–le-Bretonneux, France
| | - Margarita Pons-Salort
- Institut Pasteur, Unité de Pharmaco-Épidémiologie et Maladies Infectieuses, F–75015 Paris, France
- INSERM, U1181, F–75015 Paris, France
- Univ. Pierre et Marie Curie, Cellule Pasteur UPMC, F–75005 Paris, France
- Univ. Versailles Saint Quentin, UFR des Sciences de la Santé Simone-Veil, EA 4499, F–78180 Montigny–le-Bretonneux, France
| | - Emmanuelle Varon
- AP–HP, Hôpital Européen Georges-Pompidou, Laboratoire de Bactériologie, F–75015 Paris, France
- Centre National de Référence des Pneumocoques, F–75015 Paris, France
| | - Marie-Anne Vibet
- Institut Pasteur, Unité de Pharmaco-Épidémiologie et Maladies Infectieuses, F–75015 Paris, France
- INSERM, U1181, F–75015 Paris, France
- Univ. Pierre et Marie Curie, Cellule Pasteur UPMC, F–75005 Paris, France
| | - Caroline Ligier
- Institut Pasteur, Unité de Pharmaco-Épidémiologie et Maladies Infectieuses, F–75015 Paris, France
- INSERM, U1181, F–75015 Paris, France
- Univ. Versailles Saint Quentin, UFR des Sciences de la Santé Simone-Veil, EA 4499, F–78180 Montigny–le-Bretonneux, France
| | - Véronique Letort
- École Centrale Paris, Laboratoire de Mathématiques Appliquées aux Systèmes, F–92290 Châtenay-Malabry, France
| | - Lulla Opatowski
- Institut Pasteur, Unité de Pharmaco-Épidémiologie et Maladies Infectieuses, F–75015 Paris, France
- INSERM, U1181, F–75015 Paris, France
- Univ. Versailles Saint Quentin, UFR des Sciences de la Santé Simone-Veil, EA 4499, F–78180 Montigny–le-Bretonneux, France
| | - Didier Guillemot
- Institut Pasteur, Unité de Pharmaco-Épidémiologie et Maladies Infectieuses, F–75015 Paris, France
- INSERM, U1181, F–75015 Paris, France
- Univ. Versailles Saint Quentin, UFR des Sciences de la Santé Simone-Veil, EA 4499, F–78180 Montigny–le-Bretonneux, France
- AP–HP, Hôpital Raymond-Poincaré, Unité Fonctionnelle de Santé Publique, F–92380 Garches, France
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Dhoubhadel BG, Yasunami M, Nguyen HAT, Suzuki M, Vu TH, Thi Thuy Nguyen A, Dang DA, Yoshida LM, Ariyoshi K. Bacterial load of pneumococcal serotypes correlates with their prevalence and multiple serotypes is associated with acute respiratory infections among children less than 5 years of age. PLoS One 2014; 9:e110777. [PMID: 25360707 PMCID: PMC4216008 DOI: 10.1371/journal.pone.0110777] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Accepted: 09/18/2014] [Indexed: 12/03/2022] Open
Abstract
Background Among pneumococcal serotypes, some serotypes are more prevalent in the nasopharynx than others; determining factors for higher prevalence remain to be fully explored. As non-vaccine serotypes have emerged after the introduction of 7-valent conjugate vaccines, study of serotype specific epidemiology is in need. When two or more serotypes co-colonize, they evolve rapidly to defend host's immune responses; however, a clear association of co-colonization with a clinical outcome is lacking. Methods Children less than 5 years old who were admitted to hospital due to acute respiratory infections (ARI) (n = 595) and healthy children (n = 350) were recruited. Carriage of pneumococcus was determined by culture and lytA PCR in the nasopharyngeal samples. Serotype/serogroup detection and its quantification were done by the nanofluidic real time PCR system. Spearman's correlation and logistic regression were used to examine a correlation of serotype/serogroup specific bacterial load with its prevalence and an association of co-colonization with ARI respectively. Results Serotype/serogroup specific bacterial load was correlated with its prevalence, both in ARI cases (Spearman's rho = 0.44, n = 186; P<0.0001) and healthy children (Spearman's rho = 0.41, n = 115; P<0.0001). The prevalence of multiple serotypes was more common in ARI cases than in healthy children (18.5% vs 7.1%; aOR 2.92, 95% CI: 1.27–6.71; P = 0.01). The dominant serotype in the co-colonization had a 2 log10 higher bacterial load than the subdominant serotype, both in ARI cases (P<0.001) and healthy children (P<0.05). Conclusions High bacterial load in the nasopharynx may help transmit pneumococci among hosts, and increase the chance of successful acquisition and colonization. Co-colonization of multiple serotypes of pneumococci is linked with ARI, which infers the interactions of multiple serotypes may increase their pathogenicity; however, they may compete for growth in number.
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Affiliation(s)
- Bhim Gopal Dhoubhadel
- Department of Clinical Medicine, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan
- Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
| | - Michio Yasunami
- Department of Clinical Medicine, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan
| | - Hien Anh Thi Nguyen
- Department of Bacteriology, National Institute of Hygiene and Epidemiology, Hanoi, Vietnam
| | - Motoi Suzuki
- Department of Clinical Medicine, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan
| | - Thu Huong Vu
- Department of Bacteriology, National Institute of Hygiene and Epidemiology, Hanoi, Vietnam
| | - Ai Thi Thuy Nguyen
- Department of Microbiology, Khanh Hoa General Hospital, NhaTrang, Vietnam
| | - Duc Anh Dang
- Department of Bacteriology, National Institute of Hygiene and Epidemiology, Hanoi, Vietnam
| | - Lay-Myint Yoshida
- Department of Pediatric Infectious Diseases, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan
- * E-mail:
| | - Koya Ariyoshi
- Department of Clinical Medicine, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan
- Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
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Flasche S, Edmunds WJ, Miller E, Goldblatt D, Robertson C, Choi YH. The impact of specific and non-specific immunity on the ecology of Streptococcus pneumoniae and the implications for vaccination. Proc Biol Sci 2013; 280:20131939. [PMID: 24089337 PMCID: PMC3790488 DOI: 10.1098/rspb.2013.1939] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Accepted: 09/11/2013] [Indexed: 01/24/2023] Open
Abstract
More than 90 capsular serotypes of Streptococcus pneumoniae coexist despite competing for nasopharyngeal carriage and a gradient in fitness. The underlying mechanisms for this are poorly understood and make assessment of the likely population impact of vaccination challenging. We use an individual-based simulation model to generalize widely used deterministic models for pneumococcal competition and show that in these models short-term serotype-specific and serotype non-specific immunity could constitute the mechanism governing between-host competition and coexistence. We find that non-specific immunity induces between-host competition and that serotype-specific immunity limits a type's competitive advantage and allows stable coexistence of multiple serotypes. Serotypes carried at low prevalence show high variance in carriage levels, which would result in apparent outbreaks if they were highly pathogenic. Vaccination against few serotypes can lead to elimination of the vaccine types and induces replacement by others. However, in simulations where the elimination of the targeted types is achieved only by a combination of vaccine effects and the competitive pressure of the non-vaccine types, a universal vaccine with similar-type-specific effectiveness can fail to eliminate pneumococcal carriage and offers limited herd immunity. Hence, if vaccine effects are insufficient to control the majority of serotypes at the same time, then exploiting the competitive pressure by selective vaccination can help control the most pathogenic serotypes.
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Affiliation(s)
- Stefan Flasche
- Immunisation, Hepatitis and Blood Safety Department, Public Health England, 61 Colindale Avenue, Colindale, London NW9 5EQ, UK
- Department of Mathematics and Statistics, Strathclyde University, 26 Richmond Street, Glasgow G1 1XH, UK
- Centre for the Mathematical Modelling of Infectious Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK
| | - W. John Edmunds
- Immunisation, Hepatitis and Blood Safety Department, Public Health England, 61 Colindale Avenue, Colindale, London NW9 5EQ, UK
- Centre for the Mathematical Modelling of Infectious Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK
| | - Elizabeth Miller
- Immunisation, Hepatitis and Blood Safety Department, Public Health England, 61 Colindale Avenue, Colindale, London NW9 5EQ, UK
| | - David Goldblatt
- Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UK
| | - Chris Robertson
- Department of Mathematics and Statistics, Strathclyde University, 26 Richmond Street, Glasgow G1 1XH, UK
- Health Protection Scotland, 5 Cadogan Street, Glasgow G2 6QE, UK
- International Prevention Research Institute, 95 Cours Lafayette, Lyon 69006, France
| | - Yoon Hong Choi
- Immunisation, Hepatitis and Blood Safety Department, Public Health England, 61 Colindale Avenue, Colindale, London NW9 5EQ, UK
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Melegaro A, Choi YH, George R, Edmunds WJ, Miller E, Gay NJ. Dynamic models of pneumococcal carriage and the impact of the Heptavalent Pneumococcal Conjugate Vaccine on invasive pneumococcal disease. BMC Infect Dis 2010; 10:90. [PMID: 20377886 PMCID: PMC2867993 DOI: 10.1186/1471-2334-10-90] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2009] [Accepted: 04/08/2010] [Indexed: 11/17/2022] Open
Abstract
Background The 7-valent pneumococcal conjugate vaccine has been introduced in national immunisation programmes of most industrialised countries and recently in two African GAVI eligible countries (Rwanda and The Gambia). However the long term effects of PCV are still unclear, as beneficial direct and herd immunity effects might be countered by serotype replacement. Method A dynamic, age-structured, compartmental model of Streptococcus pneumoniae transmission was developed to predict the potential impact of PCV7 on the incidence of invasive disease accounting for both herd immunity and serotype replacement effects. The model was parameterised using epidemiological data from England and Wales and pre and post-vaccination surveillance data from the US. Results Model projections showed that serotype replacement plays a crucial role in determining the overall effect of a PCV7 vaccination programme and could reduce, negate or outweigh its beneficial impact. However, using the estimate of the competition parameter derived from the US post-vaccination experience, an infant vaccination programme would prevent 39,000 IPD cases in the 20 years after PCV7 introduction in the UK. Adding a catch-up campaign for under 2 or under 5 year olds would provide a further reduction of 1,200 or 3,300 IPD cases respectively, mostly in the first few years of the programme. Conclusions This analysis suggests that a PCV vaccination programme would eradicate vaccine serotypes from circulation. However, the increase in carriage of non-vaccine serotypes, and the consequent increase in invasive disease, could reduce, negate or outweigh the benefit. These results are sensitive to changes in the protective effect of the vaccine, and, most importantly, to the level of competition between vaccine and non-vaccine types. The techniques developed here can be used to assess the introduction of vaccination programmes in developing countries and provide the basis for cost-effectiveness analyses.
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Affiliation(s)
- Alessia Melegaro
- DONDENA Centre for Research on Social Dynamics, Bocconi University, Via Guglielmo Rontgen, Milan, Italy
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Auranen K, Mehtälä J, Tanskanen A, S Kaltoft M. Between-strain competition in acquisition and clearance of pneumococcal carriage--epidemiologic evidence from a longitudinal study of day-care children. Am J Epidemiol 2010; 171:169-76. [PMID: 19969530 PMCID: PMC2800239 DOI: 10.1093/aje/kwp351] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The state of pneumococcal carriage-that is, pneumococcal colonization in the nasopharynx of healthy persons-represents a reservoir for the spread of pneumococci among individuals. In light of the introduction of new pneumococcal conjugate vaccines, further knowledge on the dynamics of pneumococcal carriage is important. Different serotypes (strains) of pneumococcus are known to compete with each other in colonizing human hosts. Understanding the strength and mode of between-serotype competition is important because of its implications for vaccine-induced changes in the ecology of pneumococcal carriage. Competition may work through reduced acquisition of new serotypes, due to concurrent carriage in the individual, or through enhanced clearance of serotypes in carriers who harbor more than 1 serotype simultaneously. The authors employed longitudinal data (1999-2001) on pneumococcal carriage in Danish day-care children to analyze between-serotype competition. The data included observations of carriage in children who had not been vaccinated against pneumococcus, and the level of pneumococcal antibiotic resistance and antibiotic usage in the community was very low. Clearance of any single serotype was not affected by simultaneous carriage of other serotypes. In contrast, acquisition of other serotypes in already-colonized hosts was weak (relative rate of acquisition = 0.09, 95% credible interval: 0.05, 0.15).
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Affiliation(s)
- Kari Auranen
- Department of Vaccination and Immune Protection, National Institute for Health and Welfare, Mannerheimintie 166, Helsinki, Finland.
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Snedecor SJ, Strutton DR, Ciuryla V, Schwartz EJ, Botteman MF. Transmission-dynamic model to capture the indirect effects of infant vaccination with Prevnar (7-valent pneumococcal conjugate vaccine (PCV7)) in older populations. Vaccine 2009; 27:4694-703. [PMID: 19520197 DOI: 10.1016/j.vaccine.2009.05.062] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2008] [Revised: 05/13/2009] [Accepted: 05/21/2009] [Indexed: 11/26/2022]
Abstract
We developed an age-structured, transmission-dynamic, mathematical model to quantify the direct and indirect benefits of infant PCV7 vaccination. The model simulates the acquisition of asymptomatic carriage of Streptococcus pneumoniae and the development of fatal and non-fatal invasive pneumococcal disease (IPD) among vaccinated and unvaccinated individuals aged <2, 2-4, 5-17, 18-49, 50-64, and >or=65 years old. The model was parameterized using published US surveillance data, supplemented with data from published literature. The model predicts the observed incidence of IPD with good agreement and may be used to predict the impact of various vaccination strategies in the US or other populations yet to introduce PCV7.
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Abstract
In a recent experiment, we found that mice previously infected with Bordetella pertussis were not protected against a later infection with Bordetella parapertussis, while primary infection with B. parapertussis conferred cross-protection. This challenges the common assumption made in most mathematical models for pathogenic strain dynamics that cross-immunity between strains is symmetric. Here we investigate the potential consequences of this pattern on the circulation of the two pathogens in human populations. To match the empirical dominance of B. pertussis, we made the additional assumption that B. parapertussis pays a cost in terms of reduced fitness. We begin by exploring the range of parameter values that allow the coexistence of the two pathogens, with or without vaccination. We then track the dynamics of the system following the introduction of anti-pertussis vaccination. Our results suggest that (1) in order for B. pertussis to be more prevalent than B. parapertussis, the former must have a strong competitive advantage, possibly in the form of higher infectivity, and (2) because of asymmetric cross-immunity, the introduction of anti-pertussis vaccination should have little effect on the absolute prevalence of B. parapertussis. We discuss the evidence supporting these predictions, and the potential relevance of this model for other pathogens.
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15
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Rajam G, Jackson D, Pilishvili T, Whitney CG, Facklam RR, Carlone GM, Romero-Steiner S. An in vitro model to assess pneumococcal adherence to nasopharyngeal cells under competition conditions. J Microbiol Methods 2007; 70:219-26. [PMID: 17512994 DOI: 10.1016/j.mimet.2007.04.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2007] [Revised: 04/15/2007] [Accepted: 04/17/2007] [Indexed: 11/22/2022]
Abstract
Pneumococcal conjugate vaccine (PCV7) reduces invasive disease and carriage caused by vaccine serotypes (VS). An increase in carriage and disease with non-vaccine serotypes (NVS) has been observed. We have developed an in vitro model with human nasopharyngeal (NP) epithelial cells (Detroit 562) to assess the adherence capacity of Streptococcus pneumoniae to NP cells in the presence or absence of a competing Pnc strain. Two hundred and fifty pneumococcal (Pnc) strains (10 strains per serotype for 7 VS and 18 NVS) were tested for their opacity phenotype. Strains exhibiting (> or =50%) the transparent phenotype (n=72) were evaluated for their adherence capacity to Detroit 562 cells. Mean adherence capacity (> or =129 CFU/well) to NP cells was high for VS 18C, 4, and 9V and for NVS 16F, 10A, and 6A. In the in vitro competition experiments, VS strains out-competed (42/108) or co-existed (43/108) with NVS strains for adherence to NP cells in most co-inoculations. By contrast, NVS (15C, 16F, 31, and 35B) out-competed with VS in only 9 of 108 co-inoculations. Serotype 16F out-competed or co-existed with some VS and NVS strains. This model may be used to identify Pnc strains of a given serotype with competitive potentials for replacement of VS in the nasopharynx and to screen Pnc strains for animal colonization models.
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Affiliation(s)
- Gowrisankar Rajam
- Division of Bacterial Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA
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16
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Abstract
Vaccines exert strong selective pressures on pathogens, favouring the spread of antigenic variants. We propose a simple mathematical model to investigate the dynamics of a novel pathogenic strain that emerges in a population where a previous strain is maintained at low endemic level by a vaccine. We compare three methods to assess the ability of the novel strain to invade and persist: algebraic rate of invasion; deterministic dynamics; and stochastic dynamics. These three techniques provide complementary predictions on the fate of the system. In particular, we emphasize the importance of stochastic simulations, which account for the possibility of extinctions of either strain. More specifically, our model suggests that the probability of persistence of an invasive strain (i) can be minimized for intermediate levels of vaccine cross-protection (i.e. immune protection against the novel strain) and (ii) is lower if cross-immunity acts through a reduced infectious period rather than through reduced susceptibility.
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Affiliation(s)
- Olivier Restif
- Department of Veterinary Medicine, University of Cambridge, Cambridge Infectious Diseases Consortium, Madingley Road, Cambridge CB3 0ES, UK.
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17
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Käyhty H, Auranen K, Nohynek H, Dagan R, Mäkelä H. Nasopharyngeal colonization: a target for pneumococcal vaccination. Expert Rev Vaccines 2007; 5:651-67. [PMID: 17181439 DOI: 10.1586/14760584.5.5.651] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The pneumococcal conjugate vaccine (PCV), licensed in 2000, is highly efficient in preventing serious disease caused by serotypes in the vaccine and also prevents symptomless colonization of the nasopharynx. Prevention of this first step in the infection cycle has important consequences: it reduces chances of spread of the infection and indirectly protects from disease. Through these indirect effects, the protection afforded by the vaccine extends to the whole population, including those not vaccinated (herd immunity). Already now, after 5 years of wide use of PCV for infant immunization in the USA, more cases are prevented through the indirect effects than by vaccine-induced immunity in those vaccinated. The extended protection increases the cost-effectiveness of PCV and should clearly encourage its use in poorly resourced countries. However, the accumulated experience also shows that the herd immunity, due to PCV, is partly offset by replacement of the vaccine serotypes by other, nonvaccine serotypes. Owing to the general reduced virulence of the latter, this has only had a modest effect on disease, but the possibility of more virulent nonvaccine serotypes arising cannot be ignored and should be the focus of continued surveillance.
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Affiliation(s)
- Helena Käyhty
- National Public Health Institute, Department of Vaccines, Helsinki, Finland.
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18
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Cauchemez S, Temime L, Valleron AJ, Varon E, Thomas G, Guillemot D, Boëlle PY. S. pneumoniae transmission according to inclusion in conjugate vaccines: Bayesian analysis of a longitudinal follow-up in schools. BMC Infect Dis 2006; 6:14. [PMID: 16445857 PMCID: PMC1382230 DOI: 10.1186/1471-2334-6-14] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2005] [Accepted: 01/30/2006] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Recent trends of pneumococcal colonization in the United States, following the introduction of conjugate vaccination, indicate that non-vaccine serotypes tend to replace vaccine serotypes. The eventual extent of this replacement is however unknown and depends on serotype-specific carriage and transmission characteristics. METHODS Here, some of these characteristics were estimated for vaccine and non-vaccine serotypes from the follow-up of 4,488 schoolchildren in France in 2000. A Bayesian approach using Markov chain Monte Carlo data augmentation techniques was used for estimation. RESULTS Vaccine and non-vaccine serotypes were found to have similar characteristics: the mean duration of carriage was 23 days (95% credible interval (CI): 21, 25 days) for vaccine serotypes and 22 days (95% CI: 20, 24 days) for non-vaccine serotypes; within a school of size 100, the Secondary Attack Rate was 1.1% (95% CI: 1.0%, 1.2%) for both vaccine and non-vaccine serotypes. CONCLUSION This study supports that, in 3-6 years old children, no competitive advantage exists for vaccine serotypes compared to non-vaccine serotypes. This is an argument in favour of important serotype replacement. It would be important to validate the result for infants, who are known to be the main reservoir in maintaining transmission. Overall reduction in pathogenicity should also be taken into account in forecasting the future burden of pneumococcal colonization in vaccinated populations.
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Affiliation(s)
- Simon Cauchemez
- INSERM U707, Paris, France
- Université Pierre et Marie Curie, Paris, France
| | | | - Alain-Jacques Valleron
- INSERM U707, Paris, France
- Université Pierre et Marie Curie, Paris, France
- Assistance Publique – Hôpitaux de Paris, Paris, France
| | - Emmanuelle Varon
- Centre de Référence du Pneumocoque, Hôpital Européen George Pompidou, Paris, France
| | - Guy Thomas
- INSERM U707, Paris, France
- Université Pierre et Marie Curie, Paris, France
- Assistance Publique – Hôpitaux de Paris, Paris, France
| | | | - Pierre-Yves Boëlle
- INSERM U707, Paris, France
- Université Pierre et Marie Curie, Paris, France
- Assistance Publique – Hôpitaux de Paris, Paris, France
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