1
|
CALABRÒ GIOVANNAELISA, VITALE FRANCESCO, RIZZO CATERINA, PUGLIESE ANDREA, BOCCALINI SARA, BECHINI ANGELA, PANATTO DONATELLA, AMICIZIA DANIELA, DOMNICH ALEXANDER, AMODIO EMANUELE, COSTANTINO CLAUDIO, DI PIETRO MARIALUISA, SALVATI CRISTINA, D’AMBROSIO FLORIANA, ORSINI FRANCESCA, MAIDA ADA, DOMINICI ANNA, CLEMENTE DANIA, CECCI MARINA, PELLACCHIA ANDREA, DI SERAFINO FRANCESCA, BAKKER KEVIN, MALIK TUFAILMOHAMMAD, SHAROMI OLUWASEUN, BELLUZZO MIRIAM, LEONFORTE FRANCESCO, ZAGRA LUIGI, LA GATTA EMANUELE, PETRELLA LUIGI, BONANNI PAOLO, DE WAURE CHIARA. [The new 15-valent pneumococcal conjugate vaccine for the prevention of S. pneumoniae infections in pediatric age: a Health Technology Assessment]. JOURNAL OF PREVENTIVE MEDICINE AND HYGIENE 2023; 64:E1-E160. [PMID: 37655211 PMCID: PMC10468156 DOI: 10.15167/2421-4248/jpmh2023.64.1s1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 09/02/2023]
Affiliation(s)
- GIOVANNA ELISA CALABRÒ
- Sezione di Igiene, Dipartimento Universitario di Scienze della Vita e Sanità Pubblica, Università Cattolica del Sacro Cuore, Roma, Italia
- VIHTALI (Value In Health Technology and Academy for Leadership & Innovation), Spin-off dell’Università Cattolica del Sacro Cuore, Roma, Italia
| | - FRANCESCO VITALE
- Dipartimento di Promozione della Salute, Materno-Infantile, di Medicina Interna e Specialistica di Eccellenza “G. D’Alessandro”, Università degli Studi di Palermo
| | - CATERINA RIZZO
- Dipartimento di Ricerca Traslazionale e delle Nuove Tecnologie in Medicina e Chirurgia, Università degli Studi di Pisa, Pisa, Italia
| | - ANDREA PUGLIESE
- Dipartimento di Matematica, Università di Trento, Trento, Italia
| | - SARA BOCCALINI
- Dipartimento di Scienze della Salute, Università degli di Studi di Firenze, Firenze, Italia
| | - ANGELA BECHINI
- Dipartimento di Scienze della Salute, Università degli di Studi di Firenze, Firenze, Italia
| | - DONATELLA PANATTO
- Dipartimento di Scienze della Salute, Università degli Studi di Genova, Genova, Italia
- Centro Interuniversitario di Ricerca sull’Influenza e le altre Infezioni Trasmissibili (CIRI-IT), Genova, Italia
| | - DANIELA AMICIZIA
- Dipartimento di Scienze della Salute, Università degli Studi di Genova, Genova, Italia
- Centro Interuniversitario di Ricerca sull’Influenza e le altre Infezioni Trasmissibili (CIRI-IT), Genova, Italia
| | | | - EMANUELE AMODIO
- Dipartimento di Promozione della Salute, Materno-Infantile, di Medicina Interna e Specialistica di Eccellenza “G. D’Alessandro”, Università degli Studi di Palermo
| | - CLAUDIO COSTANTINO
- Dipartimento di Promozione della Salute, Materno-Infantile, di Medicina Interna e Specialistica di Eccellenza “G. D’Alessandro”, Università degli Studi di Palermo
| | - MARIA LUISA DI PIETRO
- Sezione di Igiene, Dipartimento Universitario di Scienze della Vita e Sanità Pubblica, Università Cattolica del Sacro Cuore, Roma, Italia
| | - CRISTINA SALVATI
- Dipartimento di Scienze della Salute, Università degli di Studi di Firenze, Firenze, Italia
| | - FLORIANA D’AMBROSIO
- Sezione di Igiene, Dipartimento Universitario di Scienze della Vita e Sanità Pubblica, Università Cattolica del Sacro Cuore, Roma, Italia
| | - FRANCESCA ORSINI
- Alta Scuola di Economia e Management dei Sistemi Sanitari (ALTEMS), Università Cattolica del Sacro Cuore, Roma, Italia
| | - ADA MAIDA
- Sezione di Igiene, Dipartimento Universitario di Scienze della Vita e Sanità Pubblica, Università Cattolica del Sacro Cuore, Roma, Italia
| | - ANNA DOMINICI
- Dipartimento di Medicina e Chirurgia, Università degli di Studi di Perugia, Italia
| | - DANIA CLEMENTE
- Dipartimento di Medicina e Chirurgia, Università degli di Studi di Perugia, Italia
| | - MARINA CECCI
- Dipartimento di Medicina e Chirurgia, Università degli di Studi di Perugia, Italia
| | - ANDREA PELLACCHIA
- Dipartimento di Medicina e Chirurgia, Università degli di Studi di Perugia, Italia
| | - FRANCESCA DI SERAFINO
- Dipartimento di Ricerca Traslazionale e delle Nuove Tecnologie in Medicina e Chirurgia, Università degli Studi di Pisa, Pisa, Italia
| | - KEVIN BAKKER
- Health Economic and Decision Sciences (HEDS), Biostatistics & Research Decision Sciences (BARDS), Merck Research Laboratories, West Point, Pennsylvania
| | - TUFAIL MOHAMMAD MALIK
- Health Economic and Decision Sciences (HEDS), Biostatistics & Research Decision Sciences (BARDS), Merck Research Laboratories, West Point, Pennsylvania
| | - OLUWASEUN SHAROMI
- Health Economic and Decision Sciences (HEDS), Biostatistics & Research Decision Sciences (BARDS), Merck Research Laboratories, West Point, Pennsylvania
| | - MIRIAM BELLUZZO
- Dipartimento di Promozione della Salute, Materno-Infantile, di Medicina Interna e Specialistica di Eccellenza “G. D’Alessandro”, Università degli Studi di Palermo
| | - FRANCESCO LEONFORTE
- Dipartimento di Promozione della Salute, Materno-Infantile, di Medicina Interna e Specialistica di Eccellenza “G. D’Alessandro”, Università degli Studi di Palermo
| | - LUIGI ZAGRA
- Dipartimento di Promozione della Salute, Materno-Infantile, di Medicina Interna e Specialistica di Eccellenza “G. D’Alessandro”, Università degli Studi di Palermo
| | - EMANUELE LA GATTA
- Sezione di Igiene, Dipartimento Universitario di Scienze della Vita e Sanità Pubblica, Università Cattolica del Sacro Cuore, Roma, Italia
| | - LUIGI PETRELLA
- Sezione di Igiene, Dipartimento Universitario di Scienze della Vita e Sanità Pubblica, Università Cattolica del Sacro Cuore, Roma, Italia
| | - PAOLO BONANNI
- Dipartimento di Scienze della Salute, Università degli di Studi di Firenze, Firenze, Italia
| | - CHIARA DE WAURE
- Dipartimento di Medicina e Chirurgia, Università degli di Studi di Perugia, Italia
| |
Collapse
|
2
|
Modelling the effect of within-host dynamics on the diversity of a multi-strain pathogen. J Theor Biol 2022; 548:111185. [PMID: 35700769 DOI: 10.1016/j.jtbi.2022.111185] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Revised: 05/10/2022] [Accepted: 06/01/2022] [Indexed: 11/23/2022]
Abstract
Multi-strain pathogens such as Group A Streptococcus, Streptococcus pneumoniae, and Staphylococcus aureus cause millions of infections each year with a substantial health burden. Control of multi-strain pathogens can be complicated by the high strain diversity often observed in endemic settings. It is not well understood how high strain diversity is maintained in populations, given that they compete with each other both directly (within an individual host) and indirectly (via host immunity). Previous modelling studies have investigated how indirect competition affects the prevalence and diversity of strains. However, these studies often make simplifying assumptions about the direct competition that occurs within hosts. Currently, little data is available to validate these assumptions, hence there is a need to clarify how sensitive model outputs are to these assumptions. In this study, we compare the dynamics of multi-strain pathogens under different assumptions about direct competition between strains using an agent-based model. We find that the assumptions made about direct competition can affect the epidemiological dynamics, particularly when there is no long-term immunity following infections and a low rate of importation of non-circulating strains. Our results suggest that while direct and indirect competition can each decrease strain diversity when they act in isolation, they may increase strain diversity when they act together. This finding highlights the importance of examining sensitivity to assumptions about strain competition. In particular, omitting consideration of direct competition can lead to inaccurate estimates of the likely effectiveness of control strategies as changes in strain diversity shift the level of direct strain competition.
Collapse
|
3
|
Malik TM, Mohammed-Awel J, Gumel AB, Elbasha EH. Mathematical assessment of the impact of cohort vaccination on pneumococcal carriage and serotype replacement. JOURNAL OF BIOLOGICAL DYNAMICS 2021; 15:S214-S247. [PMID: 33594952 DOI: 10.1080/17513758.2021.1884760] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Accepted: 01/20/2021] [Indexed: 06/12/2023]
Abstract
Although pneumococcal vaccines are quite effective in reducing disease burden, factors such as imperfect vaccine efficacy and serotype replacement present an important challenge against realizing direct and herd protection benefits of the vaccines. In this study, a novel mathematical model is designed and used to describe the dynamics of two Streptococcus pneumoniae (SP) serotypes, in response to the introduction of a cohort vaccination program which targets one of the two serotypes. The model is fitted to a pediatric SP carriage prevalence data from Atlanta, GA. The model, which is rigorously analysed to investigate the existence and asymptotic stability properties of the associated equilibria (in addition to exploring conditions for competitive exclusion), is simulated to assess the impact of vaccination under different levels of serotype-specific competition and illustrate the phenomenon of serotype replacement. The calibrated model is used to forecast the carriage prevalence in the pediatric cohort over 30 years.
Collapse
Affiliation(s)
- Tufail M Malik
- Merck & Co. Inc., 2000 Galloping Hill Road, Kenilworth, NJ, USA
| | | | - Abba B Gumel
- School of Mathematical and Statistical Sciences, Arizona State University, Tempe, AZ, USA
| | | |
Collapse
|
4
|
Lourenço J, Daon Y, Gori A, Obolski U. Pneumococcal Competition Modulates Antibiotic Resistance in the Pre-Vaccination Era: A Modelling Study. Vaccines (Basel) 2021; 9:265. [PMID: 33809706 PMCID: PMC8002235 DOI: 10.3390/vaccines9030265] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 03/06/2021] [Accepted: 03/09/2021] [Indexed: 11/30/2022] Open
Abstract
The ongoing emergence of antibiotic resistant strains and high frequencies of antibiotic resistance of Streptococcus pneumoniae poses a major public health challenge. How and which ecological and evolutionary mechanisms maintain the coexistence of antibiotic resistant and susceptible strains remains largely an open question. We developed an individual-based, stochastic model expanding on a previous pneumococci modelling framework. We explore how between- and within-host mechanisms of competition can sustain observed levels of resistance to antibiotics in the pre-vaccination era. Our framework considers that within-host competition for co-colonization between resistant and susceptible strains can arise via pre-existing immunity (immunological competition) or intrinsic fitness differences due to resistance costs (ecological competition). We find that beyond stochasticity, population structure or movement, competition at the within-host level can explain observed resistance frequencies. We compare our simulation results to pneumococcal antibiotic resistance data in the European region using approximate Bayesian computation. Our results demonstrate that ecological competition for co-colonization can explain the variation in co-existence of resistant and susceptible pneumococci observed in the pre-vaccination era. Furthermore, we show that within-host pneumococcal competition can facilitate the maintenance of resistance in the pre-vaccination era. Accounting for these competition-related components of pneumococcal dynamics can improve our understanding of drivers for the emergence and maintenance of antibiotic resistance in pneumococci.
Collapse
Affiliation(s)
- José Lourenço
- Department of Zoology, University of Oxford, Oxford OX1 3SZ, UK
| | - Yair Daon
- School of Public Health, Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel;
- Porter School of the Environment and Earth Sciences, Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Andrea Gori
- NIHR Global Health Research Unit on Mucosal Pathogens, Division of Infection and Immunity, University College London, London WC1E 6BT, UK;
| | - Uri Obolski
- School of Public Health, Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel;
- Porter School of the Environment and Earth Sciences, Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| |
Collapse
|
5
|
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.
Collapse
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.
| |
Collapse
|
6
|
Choi YH, Andrews N, Miller E. Estimated impact of revising the 13-valent pneumococcal conjugate vaccine schedule from 2+1 to 1+1 in England and Wales: A modelling study. PLoS Med 2019; 16:e1002845. [PMID: 31269018 PMCID: PMC6608946 DOI: 10.1371/journal.pmed.1002845] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/11/2018] [Accepted: 05/30/2019] [Indexed: 01/20/2023] Open
Abstract
BACKGROUND In October 2017, the United Kingdom Joint Committee on Vaccination and Immunisation (JCVI) recommended removal of one primary dose of the 13-valent pneumococcal conjugate vaccine (PCV13) from the existing 2+1 schedule (2, 4, 12 months). We conducted a mathematical modelling study to investigate the potential impact of a 1+1 (3, 12 month) schedule on invasive pneumococcal disease (IPD) and pneumococcal community-acquired pneumonia (CAP). Our results and those from a 1+1 immunogenicity study formed the key evidence reviewed by JCVI. METHODS AND FINDINGS We developed age-structured, dynamic, deterministic models of pneumococcal transmission in England and Wales to describe the impact on IPD of 7-valent PCV (PCV7; introduced in 2006) and PCV13 (introduced in 2010). Key transmission and vaccine parameters were estimated by fitting to carriage data from 2001/2002 and post-PCV IPD data to 2015, using vaccine coverage, mixing patterns between ages, and population data. We considered various models to investigate potential reasons for the rapid increase in non-PCV13 (non-vaccine serotype [NVT]) IPD cases since 2014. After searching a large parameter space, 500 parameter sets were identified with a likelihood statistically close to the maximum and these used to predict future cases (median, prediction range from 500 parameter sets). Our findings indicated that the emergence of individual NVTs with higher virulence resulting from ongoing replacement was likely responsible; the NVT increase was predicted to plateau from 2020. Long-term simulation results suggest that changing to a 1+1 schedule would have little overall impact, as the small increase in vaccine-type IPD would be offset by a reduction in NVT IPD. Our results were robust to changes in vaccine assumptions in a sensitivity analysis. Under the base case scenario, a change to a 1+1 schedule in 2018 was predicted to produce 31 (6, 76) additional IPD cases over five years and 83 (-10, 242) additional pneumococcal-CAP cases, with together 8 (-2, 24) additional deaths, none in children under 15 years. Long-term continuation with the 2+1 schedule, or changing to a 1+1, was predicted to sustain current reductions in IPD cases in under-64-year-olds, but cases in 65+-year-olds would continue to increase because of the effects of an aging population. Limitations of our model include difficulty in fitting to past trends in NVT IPD in some age groups and inherent uncertainty about future NVT behaviour, sparse data for defining the mixing matrix in 65+-year-olds, and the methodological challenge of defining uncertainty on predictions. CONCLUSIONS Our findings suggest that, with the current mature status of the PCV programme in England and Wales, removing one primary dose in the first year of life would have little impact on IPD or pneumococcal CAP cases or associated deaths at any age. A reduction in the number of priming doses would improve programmatic efficiency and facilitate the introduction of new vaccines by reducing the number of coadministered vaccines given at 2 and 4 months of age in the current UK schedule. Our findings should not be applied to other settings with different pneumococcal epidemiology or with immature programmes and poor herd immunity.
Collapse
Affiliation(s)
- Yoon Hong Choi
- Statistics, Modelling and Economics Department, Data and Analytical Sciences, National Infection Service, Public Health England, London, United Kingdom
| | - Nick Andrews
- Statistics, Modelling and Economics Department, Data and Analytical Sciences, National Infection Service, Public Health England, London, United Kingdom
| | - Elizabeth Miller
- Immunisation and Countermeasures Division, National Infection Service, Public Health England, London, United Kingdom
| |
Collapse
|
7
|
Davies NG, Flasche S, Jit M, Atkins KE. Within-host dynamics shape antibiotic resistance in commensal bacteria. Nat Ecol Evol 2019; 3:440-449. [PMID: 30742105 PMCID: PMC6420107 DOI: 10.1038/s41559-018-0786-x] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Accepted: 12/11/2018] [Indexed: 12/21/2022]
Abstract
The spread of antibiotic resistance, a major threat to human health, is poorly understood. Simple population-level models of bacterial transmission predict that above a certain rate of antibiotic consumption in a population, resistant bacteria should completely eliminate non-resistant strains, while below this threshold they should be unable to persist at all. This prediction stands at odds with empirical evidence showing that resistant and non-resistant strains coexist stably over a wide range of antibiotic consumption rates. Not knowing what drives this long-term coexistence is a barrier to developing evidence-based strategies for managing the spread of resistance. Here, we argue that competition between resistant and sensitive pathogens within individual hosts gives resistant pathogens a relative fitness benefit when they are rare, promoting coexistence between strains at the population level. To test this hypothesis, we embed mechanistically explicit within-host dynamics in a structurally neutral pathogen transmission model. Doing so allows us to reproduce patterns of resistance observed in the opportunistic pathogens Escherichia coli and Streptococcus pneumoniae across European countries and to identify factors that may shape resistance evolution in bacteria by modulating the intensity and outcomes of within-host competition.
Collapse
Affiliation(s)
- Nicholas G Davies
- Centre for Mathematical Modelling of Infectious Diseases, London School of Hygiene and Tropical Medicine, London, UK.
- Department for Infectious Disease Epidemiology, Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, UK.
| | - Stefan Flasche
- Centre for Mathematical Modelling of Infectious Diseases, London School of Hygiene and Tropical Medicine, London, UK
- Department for Infectious Disease Epidemiology, Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, UK
| | - Mark Jit
- Centre for Mathematical Modelling of Infectious Diseases, London School of Hygiene and Tropical Medicine, London, UK
- Department for Infectious Disease Epidemiology, Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, UK
- Modelling and Economics Unit, Public Health England, London, UK
| | - Katherine E Atkins
- Centre for Mathematical Modelling of Infectious Diseases, London School of Hygiene and Tropical Medicine, London, UK
- Department for Infectious Disease Epidemiology, Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, UK
- Centre for Global Health, Usher Institute of Population Health Sciences and Informatics, Edinburgh Medical School, The University of Edinburgh, Edinburgh, UK
| |
Collapse
|
8
|
Assessment of Postvaccine Immunity against Streptococcus pneumoniae in Patients with Asplenia, including an Analysis of Its Impact on Bacterial Flora of the Upper Respiratory Tract and Incidence of Infections. J Immunol Res 2018; 2018:1691347. [PMID: 30687764 PMCID: PMC6330813 DOI: 10.1155/2018/1691347] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Accepted: 11/29/2018] [Indexed: 11/29/2022] Open
Abstract
S. pneumoniae is a microorganism that may cause a serious threat in postsplenectomy patients due to a potentially invasive course of infection. In order to assess a protective activity after vaccination with the 23-valent vaccine, we made an analysis of the level of antibodies in patients with asplenia compared to a control group of healthy donors. Additionally, colonization by potentially pathogenic microorganisms of the upper respiratory tract was analyzed to determine the carrier state by strains with vaccine serotype. No such strains were found in the research, yet three non-vaccine-serotype strains were found. Colonization of the upper respiratory tract by potentially pathogenic microorganisms may be connected with increased susceptibility observed and incidence of infections in patients with asplenia. However, colonization by S. pneumoniae may not have an effect on the level of specific antibodies with the 23-valent vaccine against S. pneumoniae (PPV23) in postsplenectomy patients and healthy people. The response to vaccination against S. pneumoniae showed a lower level of specific antibodies in patients with splenectomy performed more than 2 years before the test than in patients with a recently removed spleen, i.e., from 1 month to 2 years before the test. Vaccination against pneumococci also has positive effects on incidence of other etiology infections, which is of high significance in the prophylaxis of infectious diseases in this group of patients.
Collapse
|
9
|
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.
Collapse
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
| |
Collapse
|
10
|
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.
Collapse
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
| |
Collapse
|
11
|
Willem L, Verelst F, Bilcke J, Hens N, Beutels P. Lessons from a decade of individual-based models for infectious disease transmission: a systematic review (2006-2015). BMC Infect Dis 2017; 17:612. [PMID: 28893198 PMCID: PMC5594572 DOI: 10.1186/s12879-017-2699-8] [Citation(s) in RCA: 72] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2016] [Accepted: 08/22/2017] [Indexed: 02/18/2023] Open
Abstract
Background Individual-based models (IBMs) are useful to simulate events subject to stochasticity and/or heterogeneity, and have become well established to model the potential (re)emergence of pathogens (e.g., pandemic influenza, bioterrorism). Individual heterogeneity at the host and pathogen level is increasingly documented to influence transmission of endemic diseases and it is well understood that the final stages of elimination strategies for vaccine-preventable childhood diseases (e.g., polio, measles) are subject to stochasticity. Even so it appears IBMs for both these phenomena are not well established. We review a decade of IBM publications aiming to obtain insights in their advantages, pitfalls and rationale for use and to make recommendations facilitating knowledge transfer within and across disciplines. Methods We systematically identified publications in Web of Science and PubMed from 2006-2015 based on title/abstract/keywords screening (and full-text if necessary) to retrieve topics, modeling purposes and general specifications. We extracted detailed modeling features from papers on established vaccine-preventable childhood diseases based on full-text screening. Results We identified 698 papers, which applied an IBM for infectious disease transmission, and listed these in a reference database, describing their general characteristics. The diversity of disease-topics and overall publication frequency have increased over time (38 to 115 annual publications from 2006 to 2015). The inclusion of intervention strategies (8 to 52) and economic consequences (1 to 20) are increasing, to the detriment of purely theoretical explorations. Unfortunately, terminology used to describe IBMs is inconsistent and ambiguous. We retrieved 24 studies on a vaccine-preventable childhood disease (covering 7 different diseases), with publication frequency increasing from the first such study published in 2008. IBMs have been useful to explore heterogeneous between- and within-host interactions, but combined applications are still sparse. The amount of missing information on model characteristics and study design is remarkable. Conclusions IBMs are suited to combine heterogeneous within- and between-host interactions, which offers many opportunities, especially to analyze targeted interventions for endemic infections. We advocate the exchange of (open-source) platforms and stress the need for consistent “branding”. Using (existing) conventions and reporting protocols would stimulate cross-fertilization between research groups and fields, and ultimately policy making in decades to come. Electronic supplementary material The online version of this article (doi:10.1186/s12879-017-2699-8) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Lander Willem
- Centre for Health Economics Research & Modeling Infectious Diseases, Vaccine and Infectious Disease Institute, University of Antwerp, Antwerp, Belgium.
| | - Frederik Verelst
- Centre for Health Economics Research & Modeling Infectious Diseases, Vaccine and Infectious Disease Institute, University of Antwerp, Antwerp, Belgium
| | - Joke Bilcke
- Centre for Health Economics Research & Modeling Infectious Diseases, Vaccine and Infectious Disease Institute, University of Antwerp, Antwerp, Belgium
| | - Niel Hens
- Centre for Health Economics Research & Modeling Infectious Diseases, Vaccine and Infectious Disease Institute, University of Antwerp, Antwerp, Belgium.,Interuniversity Institute for Biostatistics and statistical Bioinformatics, UHasselt, Hasselt, Belgium
| | - Philippe Beutels
- Centre for Health Economics Research & Modeling Infectious Diseases, Vaccine and Infectious Disease Institute, University of Antwerp, Antwerp, Belgium.,School of Public Health and Community Medicine, The University of New South Wales, Sydney, Australia
| |
Collapse
|
12
|
Ojal J, Flasche S, Hammitt LL, Akech D, Kiti MC, Kamau T, Adetifa I, Nurhonen M, Scott JAG, Auranen K. Sustained reduction in vaccine-type invasive pneumococcal disease despite waning effects of a catch-up campaign in Kilifi, Kenya: A mathematical model based on pre-vaccination data. Vaccine 2017; 35:4561-4568. [PMID: 28729018 PMCID: PMC5571446 DOI: 10.1016/j.vaccine.2017.07.019] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Revised: 07/04/2017] [Accepted: 07/05/2017] [Indexed: 01/22/2023]
Abstract
We predict a substantial decline in the carriage prevalence of vaccine serotypes. About a 56% reduction in invasive pneumococcal disease is also predicted. The decline is predicted to be sustainable ten years post-vaccination. The current vaccination schedule is unlikely to achieve elimination of vaccine serotypes.
Background In 2011, Kenya introduced the 10-valent pneumococcal conjugate vaccine together with a catch-up campaign for children aged <5 years in Kilifi County. In a post-vaccination surveillance study based in Kilifi, there was a substantial decline in invasive pneumococcal disease (IPD). However, given the continued circulation of the vaccine serotypes it is possible that vaccine-serotype disease may re-emerge once the effects of the catch-up campaign wear off. Methods We developed a compartmental, age-structured dynamic model of pneumococcal carriage and invasive disease for three serotype groups: the 10-valent vaccine serotypes and two groups of non-vaccine serotypes based on their susceptibility to mutual competition. The model was calibrated to age- and serotype-specific data on carriage and IPD in the pre-vaccination era and used to predict carriage prevalence and IPD up to ten years post-vaccination in Kilifi. The model was validated against the observed carriage prevalence after vaccine introduction. Results The model predicts a sustained reduction in vaccine-type pneumococcal carriage prevalence from 33% to 8% in infants and from 30% to 8% in 1–5 year olds over the 10-year period following vaccine introduction. The incidence of IPD is predicted to decline across all age groups resulting in an overall reduction of 56% in the population, corresponding to 10.4 cases per 100,000 per year. The vaccine-type IPD incidence is estimated to decline by 83% while non-vaccine-type IPD incidence is predicted to increase by 52%. The model's predictions of carriage prevalence agrees well with the observed data in the first five years post-vaccination. Conclusion We predict a sustained and substantial decline in IPD through PCV vaccination and that the current regimen is insufficient to fully eliminate vaccine-serotype circulation in the model. We show that the observed impact is likely to be sustained despite waning effects of the catch-up campaign.
Collapse
Affiliation(s)
- John Ojal
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine-Coast, Kilifi, Kenya; Department of Infectious Disease Epidemiology, Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, United Kingdom.
| | - Stefan Flasche
- Department of Infectious Disease Epidemiology, Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Laura L Hammitt
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine-Coast, Kilifi, Kenya; Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Donald Akech
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine-Coast, Kilifi, Kenya
| | - Moses C Kiti
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine-Coast, Kilifi, Kenya
| | - Tatu Kamau
- Kenya Ministry of Health, Nairobi, Kenya
| | - Ifedayo Adetifa
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine-Coast, Kilifi, Kenya; Department of Infectious Disease Epidemiology, Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Markku Nurhonen
- Department of Public Health Solutions, National Institute for Health and Welfare (THL), Finland
| | - J Anthony G Scott
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine-Coast, Kilifi, Kenya; Department of Infectious Disease Epidemiology, Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Kari Auranen
- Department of Public Health Solutions, National Institute for Health and Welfare (THL), Finland; Department of Mathematics and Statistics, University of Turku, Finland
| |
Collapse
|
13
|
Geographic variation in pneumococcal vaccine efficacy estimated from dynamic modeling of epidemiological data post-PCV7. Sci Rep 2017; 7:3049. [PMID: 28607461 PMCID: PMC5468270 DOI: 10.1038/s41598-017-02955-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Accepted: 04/28/2017] [Indexed: 11/09/2022] Open
Abstract
Although mean efficacy of multivalent pneumococcus vaccines has been intensively studied, variance in vaccine efficacy (VE) has been overlooked. Different net individual protection across settings can be driven by environmental conditions, local serotype and clonal composition, as well as by socio-demographic and genetic host factors. Understanding efficacy variation has implications for population-level effectiveness and other eco-evolutionary feedbacks. Here I show that realized VE can vary across epidemiological settings, by applying a multi-site-one-model approach to data post-vaccination. I analyse serotype prevalence dynamics following PCV7, in asymptomatic carriage in children attending day care in Portugal, Norway, France, Greece, Hungary and Hong-Kong. Model fitting to each dataset provides site-specific estimates for vaccine efficacy against acquisition, and pneumococcal transmission parameters. According to this model, variable serotype replacement across sites can be explained through variable PCV7 efficacy, ranging from 40% in Norway to 10% in Hong-Kong. While the details of how this effect is achieved remain to be determined, here I report three factors negatively associated with the VE readout, including initial prevalence of serotype 19F, daily mean temperature, and the Gini index. The study warrants more attention on local modulators of vaccine performance and calls for predictive frameworks within and across populations.
Collapse
|
14
|
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.
Collapse
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
| |
Collapse
|
15
|
Paulo AC, Sá-Leão R. Periodic cycles of pneumococcal serotypes carried by children before and after 7-valent pneumococcal conjugate vaccine. PLoS One 2017; 12:e0176723. [PMID: 28453533 PMCID: PMC5409052 DOI: 10.1371/journal.pone.0176723] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Accepted: 04/15/2017] [Indexed: 01/30/2023] Open
Abstract
BACKGROUND Periodic cycles in the serotype-specific incidence of invasive pneumococcal disease have been described but less is known in carriage. METHODS We analyzed serotype carriage prevalence among children 0-6 years old over a 15-year period that included pre-PCV7 data and a decade of PCV7 use. Mixed generalized additive models were used to study periodic cycles and how PCV7 impacted on them. RESULTS Pneumococcal carriage data of 7,463 children were analyzed. Periodic cycles ranging from 3 to 6 years were observed for PCV7-serotypes (VT) 14, 19F and 23F and for non-PCV7 types (NVT) 3, 6A, 6C, 11A, and NT. An indirect impact of PCV7 on periodic cycles of NVT was observed and could be translated in three ways: (i) a higher amplitude in the PCV7 period (serotypes 3 and 11A), (ii) sustained increase in the prevalence of carriage (serotypes 6C, 19A and NT) and (iii) an increase in the inter-epidemic period (serotypes 3, 6A and NT). An increase in the child's mean age of carriage of VTs 6B, 19F and 23F was observed. Serotypes 3, 6C, 11A and 15A became more frequent in ages previously associated with carriage of VTs. CONCLUSIONS Periodic cycles among serotypes frequently carried exist and can be modeled. These cycles can be perturbed upon introduction of PCVs and can lead to shifts in the mean age of carriage. Cyclic re-emergence of VTs can occur in settings with non-universal vaccine use. These results should be taken into account when interpreting surveillance data on pneumococcal carriage.
Collapse
Affiliation(s)
- Ana Cristina Paulo
- Laboratory of Molecular Microbiology of Human Pathogens, Instituto de Tecnologia Quimíca e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Raquel Sá-Leão
- Laboratory of Molecular Microbiology of Human Pathogens, Instituto de Tecnologia Quimíca e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal.,Departamento de Biologia Vegetal, Faculdade de Ciências, Universidade de Lisboa, Lisboa, Portugal
| |
Collapse
|
16
|
Flasche S, Givon-Lavi N, Dagan R. Using Pneumococcal Carriage Data to Monitor Postvaccination Changes in the Incidence of Pneumococcal Otitis Media. Am J Epidemiol 2016; 184:652-659. [PMID: 27744387 DOI: 10.1093/aje/kww012] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2015] [Accepted: 01/12/2016] [Indexed: 11/13/2022] Open
Abstract
Pneumococcal conjugate vaccines (PCVs) have substantially reduced the burden of pneumococcal disease, including the incidence of otitis media (OM). However, in most countries, no surveillance exists to monitor the change in pneumococcal OM incidence after the introduction of PCVs. We explored whether measuring pneumococcal carriage was a useful surrogate for monitoring postvaccination changes in the incidence of pneumococcal OM. The 7-valent PCV was introduced to Israel's national immunization program in July 2009 and gradually replaced by the 13-valent PCV starting in November 2010. Each day since 2009, nasopharyngeal swabs have been obtained from the first 4 Bedouin children and the first 4 Jewish children who were younger than 5 years old and attended a pediatric emergency room in southern Israel. During the same time, OM surveillance in southern Israel included all children younger than 2 years of age who were diagnosed with OM and had undergone a middle-ear fluid culture. The relative change in the prevalence of vaccine-serotype (VT) pneumococcal carriage was predictive of the relative change in incidence of OM due to VT pneumococcus. However, the serotype replacement observed in non-VT carriage is not paralleled in the incidence of OM due to non-VT pneumococcus. This could indicate that there are more complex mechanisms of the immune response involved in preventing initial and consecutive episodes of OM, which has been changed through declining prevalence of the most virulent serotypes as a result of vaccination.
Collapse
|
17
|
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.
Collapse
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
| |
Collapse
|
18
|
Mitchell PK, Lipsitch M, Hanage WP. Carriage burden, multiple colonization and antibiotic pressure promote emergence of resistant vaccine escape pneumococci. Philos Trans R Soc Lond B Biol Sci 2016; 370:20140342. [PMID: 25918447 PMCID: PMC4424439 DOI: 10.1098/rstb.2014.0342] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Pneumococcal conjugate vaccines target the limited subset of the more than 90 known serotypes of Streptococcus pneumoniae responsible for the greatest burden of pneumococcal disease and antibiotic resistance. Following the introduction of these vaccines, serotypes not targeted were able to expand and resistance became more common within these types. Here we use a stochastic dynamic model of pediatric pneumococcal carriage to evaluate potential influences on the emergence of new resistant lineages following the introduction of a vaccine targeting more common resistant types. Antibiotic pressure was the strongest driver, with no emergence at low levels and universal emergence at high levels. At intermediate levels of antibiotic pressure, higher carriage burden and a greater degree of dual carriage promoted emergence. This may have implications for current plans to introduce childhood pneumococcal vaccination in several high-burden countries.
Collapse
Affiliation(s)
- Patrick K Mitchell
- Center for Communicable Disease Dynamics, Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA
| | - Marc Lipsitch
- Center for Communicable Disease Dynamics, Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA
| | - William P Hanage
- Center for Communicable Disease Dynamics, Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA
| |
Collapse
|
19
|
Nguyen CT, Park SS, Rhee DK. Stress responses in Streptococcus species and their effects on the host. J Microbiol 2015; 53:741-9. [PMID: 26502957 DOI: 10.1007/s12275-015-5432-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Revised: 09/30/2015] [Accepted: 09/30/2015] [Indexed: 12/15/2022]
Abstract
Streptococci cause a variety of diseases, such as dental caries, pharyngitis, meningitis, pneumonia, bacteremia, endocarditis, erysipelas, and necrotizing fasciitis. The natural niche of this genus of bacteria ranges from the mouth and nasopharynx to the skin, indicating that the bacteria will inevitably be subjected to environmental changes during invasion into the host, where it is exposed to the host immune system. Thus, the Streptococcus-host interaction determines whether bacteria are cleared by the host's defenses or whether they survive after invasion to cause serious diseases. If this interaction was to be deciphered, it could aid in the development of novel preventive and therapeutic agents. Streptococcus species possess many virulent factors, such as peroxidases and heat-shock proteins (HSPs), which play key roles in protecting the bacteria from hostile host environments. This review will discuss insights into the mechanism(s) by which streptococci adapt to host environments. Additionally, we will address how streptococcal infections trigger host stress responses; however, the mechanism by which bacterial components modulate host stress responses remains largely unknown.
Collapse
Affiliation(s)
- Cuong Thach Nguyen
- School of Pharmacy, Sungkyunkwan University, Su-Won, 16419, Republic of Korea
| | - Sang-Sang Park
- School of Pharmacy, Sungkyunkwan University, Su-Won, 16419, Republic of Korea
| | - Dong-Kwon Rhee
- School of Pharmacy, Sungkyunkwan University, Su-Won, 16419, Republic of Korea.
| |
Collapse
|
20
|
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.
Collapse
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
| |
Collapse
|
21
|
Vaccination Drives Changes in Metabolic and Virulence Profiles of Streptococcus pneumoniae. PLoS Pathog 2015; 11:e1005034. [PMID: 26181911 PMCID: PMC4504489 DOI: 10.1371/journal.ppat.1005034] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Accepted: 06/19/2015] [Indexed: 11/20/2022] Open
Abstract
The bacterial pathogen, Streptococcus pneumoniae (the pneumococcus), is a leading cause of life-threatening illness and death worldwide. Available conjugate vaccines target only a small subset (up to 13) of >90 known capsular serotypes of S. pneumoniae and, since their introduction, increases in non-vaccine serotypes have been recorded in several countries: a phenomenon termed Vaccine Induced Serotype Replacement (VISR). Here, using a combination of mathematical modelling and whole genome analysis, we show that targeting particular serotypes through vaccination can also cause their metabolic and virulence-associated components to transfer through recombination to non-vaccine serotypes: a phenomenon we term Vaccine-Induced Metabolic Shift (VIMS). Our results provide a novel explanation for changes observed in the population structure of the pneumococcus following vaccination, and have important implications for strain-targeted vaccination in a range of infectious disease systems.
Collapse
|
22
|
|
23
|
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.
Collapse
|
24
|
Metcalf CJE, Andreasen V, Bjørnstad ON, Eames K, Edmunds WJ, Funk S, Hollingsworth TD, Lessler J, Viboud C, Grenfell BT. Seven challenges in modeling vaccine preventable diseases. Epidemics 2015; 10:11-5. [PMID: 25843375 PMCID: PMC6777947 DOI: 10.1016/j.epidem.2014.08.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2014] [Revised: 06/19/2014] [Accepted: 08/18/2014] [Indexed: 11/22/2022] Open
Abstract
Vaccination has been one of the most successful public health measures since the introduction of basic sanitation. Substantial mortality and morbidity reductions have been achieved via vaccination against many infections, and the list of diseases that are potentially controllable by vaccines is growing steadily. We introduce key challenges for modeling in shaping our understanding and guiding policy decisions related to vaccine preventable diseases.
Collapse
Affiliation(s)
- C J E Metcalf
- Department of Ecology and Evolutionary Biology and the Woodrow Wilson School, Princeton University, Princeton, NJ, USA.
| | - V Andreasen
- Department of Science, Systems and Models, Universitetsvej 1, 27.1, DK-4000 Roskilde, Denmark
| | - O N Bjørnstad
- Centre for Infectious Disease Dynamics, the Pennsylvania State University, State College, PA, USA
| | - K Eames
- Centre for the Mathematical Modelling of Infectious Diseases, London School of Hygiene & Tropical Medicine, London, UK
| | - W J Edmunds
- Centre for the Mathematical Modelling of Infectious Diseases, London School of Hygiene & Tropical Medicine, London, UK
| | - S Funk
- Centre for the Mathematical Modelling of Infectious Diseases, London School of Hygiene & Tropical Medicine, London, UK
| | - T D Hollingsworth
- Warwick Mathematics Institute, University of Warwick, Coventry CV4 7AL, UK; School of Life Sciences, University of Warwick, Coventry CV4 7AL, UK; Department of Clinical Sciences, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
| | - J Lessler
- Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - C Viboud
- Division of Epidemiology and Population Studies, Fogarty International Center, National Institutes of Health, Bethesda, MD, USA
| | - B T Grenfell
- Department of Ecology and Evolutionary Biology and the Woodrow Wilson School, Princeton University, Princeton, NJ, USA; Division of Epidemiology and Population Studies, Fogarty International Center, National Institutes of Health, Bethesda, MD, USA
| |
Collapse
|
25
|
Abstract
Host immunity is a major driver of pathogen evolution and thus a major determinant of pathogen diversity. Explanations for pathogen diversity traditionally assume simple interactions between pathogens and the immune system, a view encapsulated by the susceptible-infected-recovered (SIR) model. However, there is growing evidence that the complexity of many host-pathogen interactions is dynamically important. This revised perspective requires broadening the definition of a pathogen's immunological phenotype, or what can be thought of as its immunological niche. After reviewing evidence that interactions between pathogens and host immunity drive much of pathogen evolution, I introduce the concept of a pathogen's immunological phenotype. Models that depart from the SIR paradigm demonstrate the utility of this perspective and show that it is particularly useful in understanding vaccine-induced evolution. This paper highlights questions in immunology, evolution, and ecology that must be answered to advance theories of pathogen diversity.
Collapse
Affiliation(s)
- Sarah Cobey
- Department of Ecology and Evolution, University of Chicago, Chicago, Illinois
| |
Collapse
|