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Asplin P, Keeling MJ, Mancy R, Hill EM. Epidemiological and health economic implications of symptom propagation in respiratory pathogens: A mathematical modelling investigation. PLoS Comput Biol 2024; 20:e1012096. [PMID: 38701066 PMCID: PMC11095726 DOI: 10.1371/journal.pcbi.1012096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Revised: 05/15/2024] [Accepted: 04/19/2024] [Indexed: 05/05/2024] Open
Abstract
BACKGROUND Respiratory pathogens inflict a substantial burden on public health and the economy. Although the severity of symptoms caused by these pathogens can vary from asymptomatic to fatal, the factors that determine symptom severity are not fully understood. Correlations in symptoms between infector-infectee pairs, for which evidence is accumulating, can generate large-scale clusters of severe infections that could be devastating to those most at risk, whilst also conceivably leading to chains of mild or asymptomatic infections that generate widespread immunity with minimal cost to public health. Although this effect could be harnessed to amplify the impact of interventions that reduce symptom severity, the mechanistic representation of symptom propagation within mathematical and health economic modelling of respiratory diseases is understudied. METHODS AND FINDINGS We propose a novel framework for incorporating different levels of symptom propagation into models of infectious disease transmission via a single parameter, α. Varying α tunes the model from having no symptom propagation (α = 0, as typically assumed) to one where symptoms always propagate (α = 1). For parameters corresponding to three respiratory pathogens-seasonal influenza, pandemic influenza and SARS-CoV-2-we explored how symptom propagation impacted the relative epidemiological and health-economic performance of three interventions, conceptualised as vaccines with different actions: symptom-attenuating (labelled SA), infection-blocking (IB) and infection-blocking admitting only mild breakthrough infections (IB_MB). In the absence of interventions, with fixed underlying epidemiological parameters, stronger symptom propagation increased the proportion of cases that were severe. For SA and IB_MB, interventions were more effective at reducing prevalence (all infections and severe cases) for higher strengths of symptom propagation. For IB, symptom propagation had no impact on effectiveness, and for seasonal influenza this intervention type was more effective than SA at reducing severe infections for all strengths of symptom propagation. For pandemic influenza and SARS-CoV-2, at low intervention uptake, SA was more effective than IB for all levels of symptom propagation; for high uptake, SA only became more effective under strong symptom propagation. Health economic assessments found that, for SA-type interventions, the amount one could spend on control whilst maintaining a cost-effective intervention (termed threshold unit intervention cost) was very sensitive to the strength of symptom propagation. CONCLUSIONS Overall, the preferred intervention type depended on the combination of the strength of symptom propagation and uptake. Given the importance of determining robust public health responses, we highlight the need to gather further data on symptom propagation, with our modelling framework acting as a template for future analysis.
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Affiliation(s)
- Phoebe Asplin
- EPSRC & MRC Centre for Doctoral Training in Mathematics for Real-World Systems, University of Warwick, Coventry, United Kingdom
- Mathematics Institute, University of Warwick, Coventry, United Kingdom
- The Zeeman Institute for Systems Biology & Infectious Disease Epidemiology Research, University of Warwick, Coventry, United Kingdom
| | - Matt J. Keeling
- Mathematics Institute, University of Warwick, Coventry, United Kingdom
- The Zeeman Institute for Systems Biology & Infectious Disease Epidemiology Research, University of Warwick, Coventry, United Kingdom
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
| | - Rebecca Mancy
- School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow, United Kingdom
- MRC/CSO Social and Public Health Sciences Unit, University of Glasgow, Glasgow, United Kingdom
| | - Edward M. Hill
- Mathematics Institute, University of Warwick, Coventry, United Kingdom
- The Zeeman Institute for Systems Biology & Infectious Disease Epidemiology Research, University of Warwick, Coventry, United Kingdom
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Servadio JL, Choisy M, Thai PQ, Boni MF. Influenza vaccination allocation in tropical settings under constrained resources. MEDRXIV : THE PREPRINT SERVER FOR HEALTH SCIENCES 2024:2024.02.08.24302551. [PMID: 38370625 PMCID: PMC10871372 DOI: 10.1101/2024.02.08.24302551] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2024]
Abstract
Influenza virus seasonality, synchronicity, and vaccine supply differ substantially between temperate and tropical settings, and optimal vaccination strategy may differ on this basis. Most national vaccine recommendations focus on high-risk groups, elderly populations, and healthcare workers despite previous analyses demonstrating broad benefits to vaccinating younger high-contact age groups. Here, we parameterized an age-structured non-seasonal asynchronous epidemiological model of influenza virus transmission for a tropical low-income setting. We evaluated timing and age allocation of vaccines across vaccine supplies ranging from 10% to 90% using decade-based age groups. Year-round vaccination was beneficial when comparing to vaccination strategies focused on a particular time of year. When targeting a single age-group for vaccine prioritization, maximum vaccine allocation to the 10-19 high-contact age group minimized annual influenza mortality for all but one vaccine supply. When evaluating across all possible age allocations, optimal strategies always allocated a plurality of vaccines to school-age children (10-19). The converse however was not true as not all strategies allocating a plurality to children aged 10-19 minimized mortality. Allocating a high proportion of vaccine supply to the 10-19 age group is necessary but not sufficient to minimize annual mortality as distribution of remaining vaccine doses to other age groups also needs to be optimized. Strategies focusing on indirect benefits (vaccinating children) showed higher variance in mortality outcomes than strategies focusing on direct benefits (vaccinating the elderly). However, the indirect benefit approaches showed lower mean mortality and lower minimum mortality than vaccination focused on the elderly.
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Affiliation(s)
- Joseph L Servadio
- Center for Infectious Disease Dynamics and Department of Biology, Pennsylvania State University, University Park, PA, United States
- Department of Biology, Temple University, Philadelphia, PA, United States
| | - Marc Choisy
- Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Pham Quang Thai
- National Institute of Hygiene and Epidemiology, Hanoi, Vietnam
- School of Preventative Medicine and Public Health, Hanoi Medical University, Hanoi, Vietnam
| | - Maciej F Boni
- Center for Infectious Disease Dynamics and Department of Biology, Pennsylvania State University, University Park, PA, United States
- Department of Biology, Temple University, Philadelphia, PA, United States
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
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Servadio JL, Thai PQ, Choisy M, Boni MF. Repeatability and timing of tropical influenza epidemics. PLoS Comput Biol 2023; 19:e1011317. [PMID: 37467254 PMCID: PMC10389745 DOI: 10.1371/journal.pcbi.1011317] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Accepted: 06/29/2023] [Indexed: 07/21/2023] Open
Abstract
Much of the world experiences influenza in yearly recurring seasons, particularly in temperate areas. These patterns can be considered repeatable if they occur predictably and consistently at the same time of year. In tropical areas, including southeast Asia, timing of influenza epidemics is less consistent, leading to a lack of consensus regarding whether influenza is repeatable. This study aimed to assess repeatability of influenza in Vietnam, with repeatability defined as seasonality that occurs at a consistent time of year with low variation. We developed a mathematical model incorporating parameters to represent periods of increased transmission and then fitted the model to data collected from sentinel hospitals throughout Vietnam as well as four temperate locations. We fitted the model for individual (sub)types of influenza as well as all combined influenza throughout northern, central, and southern Vietnam. Repeatability was evaluated through the variance of the timings of peak transmission. Model fits from Vietnam show high variance (sd = 64-179 days) in peak transmission timing, with peaks occurring at irregular intervals and throughout different times of year. Fits from temperate locations showed regular, annual epidemics in winter months, with low variance in peak timings (sd = 32-57 days). This suggests that influenza patterns are not repeatable or seasonal in Vietnam. Influenza prevention in Vietnam therefore cannot rely on anticipation of regularly occurring outbreaks.
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Affiliation(s)
- Joseph L Servadio
- Center for Infectious Disease Dynamics and Department of Biology, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Pham Quang Thai
- National Institute of Hygiene and Epidemiology, Hanoi, Vietnam
- School of Preventative Medicine and Public Health, Hanoi Medical University, Hanoi, Vietnam
| | - Marc Choisy
- Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Maciej F Boni
- Center for Infectious Disease Dynamics and Department of Biology, Pennsylvania State University, University Park, Pennsylvania, United States of America
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
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Leng T, Hill EM, Thompson RN, Tildesley MJ, Keeling MJ, Dyson L. Assessing the impact of lateral flow testing strategies on within-school SARS-CoV-2 transmission and absences: A modelling study. PLoS Comput Biol 2022; 18:e1010158. [PMID: 35622860 PMCID: PMC9182264 DOI: 10.1371/journal.pcbi.1010158] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 06/09/2022] [Accepted: 05/02/2022] [Indexed: 12/05/2022] Open
Abstract
Rapid testing strategies that replace the isolation of close contacts through the use of lateral flow device tests (LFTs) have been suggested as a way of controlling SARS-CoV-2 transmission within schools that maintain low levels of pupil absences. We developed an individual-based model of a secondary school formed of exclusive year group bubbles (five year groups, with 200 pupils per year) to assess the likely impact of strategies using LFTs in secondary schools over the course of a seven-week half-term on transmission, absences, and testing volume, compared to a policy of isolating year group bubbles upon a pupil returning a positive polymerase chain reaction (PCR) test. We also considered the sensitivity of results to levels of participation in rapid testing and underlying model assumptions. While repeated testing of year group bubbles following case detection is less effective at reducing infections than a policy of isolating year group bubbles, strategies involving twice weekly mass testing can reduce infections to lower levels than would occur under year group isolation. By combining regular testing with serial contact testing or isolation, infection levels can be reduced further still. At high levels of pupil participation in lateral flow testing, strategies replacing the isolation of year group bubbles with testing substantially reduce absences, but require a high volume of testing. Our results highlight the conflict between the goals of minimising within-school transmission, minimising absences and minimising testing burden. While rapid testing strategies can reduce school transmission and absences, they may lead to a large number of daily tests. During the COVID-19 pandemic, a range of measures have been implemented to reduce transmission in schools. If an infected pupil is detected, one approach involves ‘isolating’ their contacts, who must then remain at home and not attend school. However, this may lead to high levels of pupil absences, which in turn may impact educational attainment. An alternative approach involves testing the contacts of infected individuals each day, who are allowed to attend school if they test negative. This can be achieved using lateral flow device tests, which can be taken at home and return a result in under thirty minutes. In this paper, using an individual-based model, we compare the impact of strategies that use lateral flow device tests to rapidly test secondary school pupils to strategies that require the contacts of infected individuals to isolate. We find that a strategy that combines testing pupils regularly with testing the contacts of identified infected individuals for a period of seven days has the potential to keep both transmission and absences low. However, such a strategy requires a high number of tests. Our results demonstrate the conflict between the competing aims of minimising transmission, minimising absences, and minimising test burden.
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Affiliation(s)
- Trystan Leng
- The Zeeman Institute for Systems Biology & Infectious Disease Epidemiology Research, School of Life Sciences and Mathematics Institute, University of Warwick, Coventry, United Kingdom
- JUNIPER – Joint UNIversities Pandemic and Epidemiological Research, https://maths.org/juniper/
- * E-mail:
| | - Edward M. Hill
- The Zeeman Institute for Systems Biology & Infectious Disease Epidemiology Research, School of Life Sciences and Mathematics Institute, University of Warwick, Coventry, United Kingdom
- JUNIPER – Joint UNIversities Pandemic and Epidemiological Research, https://maths.org/juniper/
| | - Robin N. Thompson
- The Zeeman Institute for Systems Biology & Infectious Disease Epidemiology Research, School of Life Sciences and Mathematics Institute, University of Warwick, Coventry, United Kingdom
- JUNIPER – Joint UNIversities Pandemic and Epidemiological Research, https://maths.org/juniper/
| | - Michael J. Tildesley
- The Zeeman Institute for Systems Biology & Infectious Disease Epidemiology Research, School of Life Sciences and Mathematics Institute, University of Warwick, Coventry, United Kingdom
- JUNIPER – Joint UNIversities Pandemic and Epidemiological Research, https://maths.org/juniper/
| | - Matt J. Keeling
- The Zeeman Institute for Systems Biology & Infectious Disease Epidemiology Research, School of Life Sciences and Mathematics Institute, University of Warwick, Coventry, United Kingdom
- JUNIPER – Joint UNIversities Pandemic and Epidemiological Research, https://maths.org/juniper/
| | - Louise Dyson
- The Zeeman Institute for Systems Biology & Infectious Disease Epidemiology Research, School of Life Sciences and Mathematics Institute, University of Warwick, Coventry, United Kingdom
- JUNIPER – Joint UNIversities Pandemic and Epidemiological Research, https://maths.org/juniper/
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BOCCALINI SARA, PARIANI ELENA, CALABRÒ GIOVANNAELISA, DE WAURE CHIARA, PANATTO DONATELLA, AMICIZIA DANIELA, LAI PIEROLUIGI, RIZZO CATERINA, AMODIO EMANUELE, VITALE FRANCESCO, CASUCCIO ALESSANDRA, DI PIETRO MARIALUISA, GALLI CRISTINA, BUBBA LAURA, PELLEGRINELLI LAURA, VILLANI LEONARDO, D’AMBROSIO FLORIANA, CAMINITI MARTA, LORENZINI ELISA, FIORETTI PAOLA, MICALE ROSANNATINDARA, FRUMENTO DAVIDE, CANTOVA ELISA, PARENTE FLAVIO, TRENTO GIACOMO, SOTTILE SARA, PUGLIESE ANDREA, BIAMONTE MASSIMILIANOALBERTO, GIORGETTI DUCCIO, MENICACCI MARCO, D’ANNA ANTONIO, AMMOSCATO CLAUDIA, LA GATTA EMANUELE, BECHINI ANGELA, BONANNI PAOLO. [Health Technology Assessment (HTA) of the introduction of influenza vaccination for Italian children with Fluenz Tetra ®]. JOURNAL OF PREVENTIVE MEDICINE AND HYGIENE 2021; 62:E1-E118. [PMID: 34909481 PMCID: PMC8639053 DOI: 10.15167/2421-4248/jpmh2021.62.2s1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- SARA BOCCALINI
- Dipartimento di Scienze della Salute, Università degli Studi di Firenze, Firenze, Italia
- Autore corrispondente: Sara Boccalini, Dipartimento di Scienze della Salute, Università degli Studi di Firenze, 50134 Firenze, Italia - Tel.: 055-2751084 - E-mail:
| | - ELENA PARIANI
- Dipartimento di Scienze Biomediche per la Salute, Università degli Studi di Milano, Milano, Italia
- Centro Interuniversitario per la Ricerca sull'Influenza e le altre Infezioni Trasmissibili CIRI-IT, Italia
| | - 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
| | - CHIARA DE WAURE
- Dipartimento di Medicina e Chirurgia, Università degli Studi di Perugia, Perugia, Italia
| | - DONATELLA PANATTO
- Centro Interuniversitario per la Ricerca sull'Influenza e le altre Infezioni Trasmissibili CIRI-IT, Italia
- Dipartimento di Scienze della Salute, Università degli Studi di Genova, Genova, Italia
| | - DANIELA AMICIZIA
- Centro Interuniversitario per la Ricerca sull'Influenza e le altre Infezioni Trasmissibili CIRI-IT, Italia
- Dipartimento di Scienze della Salute, Università degli Studi di Genova, Genova, Italia
| | - PIERO LUIGI LAI
- Centro Interuniversitario per la Ricerca sull'Influenza e le altre Infezioni Trasmissibili CIRI-IT, Italia
- Dipartimento di Scienze della Salute, Università degli Studi di Genova, Genova, Italia
| | - CATERINA RIZZO
- Area Funzionale Percorsi Clinici ed Epidemiologia, Ospedale Pediatrico Bambino Gesù, IRCCS, Roma, Italia
| | - EMANUELE AMODIO
- Dipartimento Promozione della Salute, Materno-Infantile, di Medicina Interna e Specialistica di Eccellenza “G. D'Alessandro”, Università degli Studi di Palermo, Palermo, Italia
| | - FRANCESCO VITALE
- Dipartimento Promozione della Salute, Materno-Infantile, di Medicina Interna e Specialistica di Eccellenza “G. D'Alessandro”, Università degli Studi di Palermo, Palermo, Italia
| | - ALESSANDRA CASUCCIO
- Dipartimento Promozione della Salute, Materno-Infantile, di Medicina Interna e Specialistica di Eccellenza “G. D'Alessandro”, Università degli Studi di Palermo, Palermo, Italia
| | - MARIA LUISA DI PIETRO
- Sezione di Igiene, Dipartimento Universitario di Scienze della Vita e Sanità Pubblica, Università Cattolica del Sacro Cuore, Roma, Italia
| | - CRISTINA GALLI
- Dipartimento di Scienze Biomediche per la Salute, Università degli Studi di Milano, Milano, Italia
| | - LAURA BUBBA
- Dipartimento di Scienze Biomediche per la Salute, Università degli Studi di Milano, Milano, Italia
| | - LAURA PELLEGRINELLI
- Dipartimento di Scienze Biomediche per la Salute, Università degli Studi di Milano, Milano, Italia
| | - LEONARDO VILLANI
- Sezione di Igiene, Dipartimento Universitario di Scienze della Vita e Sanità Pubblica, Università Cattolica del Sacro Cuore, Roma, Italia
| | - FLORIANA D’AMBROSIO
- Sezione di Igiene, Dipartimento Universitario di Scienze della Vita e Sanità Pubblica, Università Cattolica del Sacro Cuore, Roma, Italia
| | - MARTA CAMINITI
- Dipartimento di Medicina e Chirurgia, Università degli Studi di Perugia, Perugia, Italia
| | - ELISA LORENZINI
- Dipartimento di Medicina e Chirurgia, Università degli Studi di Perugia, Perugia, Italia
| | - PAOLA FIORETTI
- Dipartimento di Medicina e Chirurgia, Università degli Studi di Perugia, Perugia, Italia
| | | | - DAVIDE FRUMENTO
- Dipartimento di Scienze della Salute, Università degli Studi di Genova, Genova, Italia
| | - ELISA CANTOVA
- Dipartimento di Scienze della Salute, Università degli Studi di Genova, Genova, Italia
| | - FLAVIO PARENTE
- Dipartimento di Scienze della Salute, Università degli Studi di Genova, Genova, Italia
| | - GIACOMO TRENTO
- Dipartimento di Scienze della Salute, Università degli Studi di Genova, Genova, Italia
| | - SARA SOTTILE
- Università degli Studi di Trento, Trento, Italia
| | | | | | - DUCCIO GIORGETTI
- Dipartimento di Scienze della Salute, Università degli Studi di Firenze, Firenze, Italia
| | - MARCO MENICACCI
- Dipartimento di Scienze della Salute, Università degli Studi di Firenze, Firenze, Italia
| | - ANTONIO D’ANNA
- Dipartimento Promozione della Salute, Materno-Infantile, di Medicina Interna e Specialistica di Eccellenza “G. D'Alessandro”, Università degli Studi di Palermo, Palermo, Italia
| | - CLAUDIA AMMOSCATO
- Dipartimento Promozione della Salute, Materno-Infantile, di Medicina Interna e Specialistica di Eccellenza “G. D'Alessandro”, Università degli Studi di Palermo, Palermo, Italia
| | - EMANUELE LA GATTA
- Sezione di Igiene, Dipartimento Universitario di Scienze della Vita e Sanità Pubblica, Università Cattolica del Sacro Cuore, Roma, Italia
| | - ANGELA BECHINI
- Dipartimento di Scienze della Salute, Università degli Studi di Firenze, Firenze, Italia
| | - PAOLO BONANNI
- Dipartimento di Scienze della Salute, Università degli Studi di Firenze, Firenze, Italia
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