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Khanam F, Kim DR, Liu X, Voysey M, Pitzer VE, Zaman K, Pollard AJ, Qadri F, Clemens JD. Assessment of vaccine herd protection in a cluster-randomised trial of Vi conjugate vaccine against typhoid fever: results of further analysis. EClinicalMedicine 2023; 58:101925. [PMID: 37090439 PMCID: PMC10114505 DOI: 10.1016/j.eclinm.2023.101925] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Revised: 03/07/2023] [Accepted: 03/09/2023] [Indexed: 04/25/2023] Open
Abstract
Background A cluster-randomised trial of Vi-tetanus toxoid (Vi-TT) conjugate vaccine conducted in urban Bangladeshi children found a high level of direct protection by Vi-TT but no significant vaccine herd protection. We reassessed the trial using a "fried egg" analysis to evaluate whether herd protection might have been obscured by transmission of typhoid into the clusters from the outside. Methods A participant- and observer-blind, cluster-randomised trial was conducted between February 14, 2018 and August 12, 2019 in three wards of Mirpur, a densely populated urban area of Dhaka, Bangladesh. Children 9 months to under 16 years of age in 150 geographic clusters, which had a total of 311,289 persons present at baseline or entering during follow-up, were randomised by cluster to a single-dose of Vi-TT or Japanese encephalitis (JE) vaccine. Vi-TT protection against typhoid fever, detected at 8 treatment centres serving the study population, was compared in the original clusters for the trial, and for progressively more central subclusters ("yolks" of the "fried egg") of the cluster residents. If transmission of typhoid into the clusters had diluted observed vaccine herd protection, we hypothesised that analysis of the innermost "yolks" would reveal vaccine herd protection that was not evident in analysis of the entire clusters. The trial is registered at www.isrctn.com as ISRCTN11643110. Findings At ≤18 months of follow-up, total vaccine effectiveness (protection of Vi-TT recipients relative to JE vaccine recipients) was 85% (95% CI: 76%, 90%); indirect effectiveness (protection of non-Vi-TT recipients in Vi-TT clusters relative to non-JE vaccine recipients in JE vaccine clusters) was 17% (95% CI: -13%, 40%); and overall effectiveness (protection of all residents in the Vi-TT clusters relative to all residents of the JE vaccine clusters) was 57% (95% CI: 44%, 66%). Analyses of subpopulations in inner 75%, 50% and 25% "yolks" of the clusters failed to reveal significant changes in any of these estimates. Interpretation Our analysis did not reveal Vi-TT herd protection in the trial. Consideration should be given to exploring whether targeting adults as well as children with Vi-TT yields appreciable levels of vaccine herd protection. Funding Bill & Melinda Gates Foundation (OPP1151153, INV-025388).
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Affiliation(s)
- Farhana Khanam
- International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), Dhaka, Bangladesh
- Corresponding author. Infectious Diseases Division, International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh.
| | | | - Xinxue Liu
- Oxford Vaccine Group, Department of Paediatrics, University of Oxford and the NIHR Oxford Biomedical Research Centre, Oxford, UK
| | - Merryn Voysey
- Oxford Vaccine Group, Department of Paediatrics, University of Oxford and the NIHR Oxford Biomedical Research Centre, Oxford, UK
| | - Virginia E. Pitzer
- Department of Epidemiology of Microbial Disease and Public Health Modeling Unit, Yale School of Public Health, Yale University, New Haven, CT, USA
| | - K. Zaman
- International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), Dhaka, Bangladesh
| | - Andrew J. Pollard
- Oxford Vaccine Group, Department of Paediatrics, University of Oxford and the NIHR Oxford Biomedical Research Centre, Oxford, UK
| | - Firdausi Qadri
- International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), Dhaka, Bangladesh
| | - John D. Clemens
- International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), Dhaka, Bangladesh
- International Vaccine Institute, Seoul, South Korea
- Department of Epidemiology, UCLA Fielding School of Public Health, Los Angeles, CA, USA
- Center for Vaccine Innovation, Korea University, Seoul, South Korea
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2
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Chowdhury F, Aziz AB, Ahmmed F, Ahmed T, Kang SS, Im J, Park J, Tadesse BT, Islam MT, Kim DR, Hoque M, Pak G, Khanam F, McMillan NAJ, Liu X, Zaman K, Khan AI, Kim JH, Marks F, Qadri F, Clemens JD. The interplay between WASH practices and vaccination with oral cholera vaccines in protecting against cholera in urban Bangladesh: Reanalysis of a cluster-randomized trial. Vaccine 2023; 41:2368-2375. [PMID: 36898931 PMCID: PMC10102718 DOI: 10.1016/j.vaccine.2023.02.054] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2022] [Revised: 02/06/2023] [Accepted: 02/16/2023] [Indexed: 03/11/2023]
Abstract
The current global initiative to end Cholera by 2030 emphasizes the use of oral cholera vaccine (OCV) combined with feasible household Water-Sanitation-Hygiene (WASH) interventions. However, little is known about how improved WASH practices and behaviors and OCV interact to reduce the risk of cholera. We reanalyzed two arms of a cluster-randomized trial in urban Bangladesh, to evaluate the effectiveness of OCV given as a 2-dose regimen. One arm (30 clusters, n = 94,675) was randomized to vaccination of persons aged one year and older with OCV, and the other arm (30 clusters, n = 80,056) to no intervention. We evaluated the prevention of cholera by household WASH, classified at baseline using a previously validated rule, and OCV over 2 years of follow-up. When analyzed by assignment to OCV clusters rather than receipt of OCV, in comparison to persons living in "Not Better WASH" households in the control clusters, reduction of severe cholera (the primary outcome) was similar for persons in "Not Better WASH" households in vaccine clusters (46%, 95% CI:24,62), for persons in "Better WASH" households in the control clusters (48%, 95% CI:25,64), and for persons in "Better WASH" households in the vaccine clusters (48%, 95% CI:16,67). In contrast, when analyzed by actual receipt of a complete OCV regimen, , in comparison to persons in "Not Better WASH" households in the control clusters, protection against severe cholera increased steadily from 39% (95% CI:13,58) in residents of "Better WASH" households in the control clusters to 57% (95% CI:35,72) in vaccinated persons in "Not Better WASH" households to 63% (95% CI:21,83) in vaccinated persons in "Better WASH" households. This analysis suggests that improved household WASH and OCV received may interact to provide greater protection against cholera. However, the divergence between findings related to intent to vaccinate versus those pertaining to actual receipt of OCV underscores the need for further research on this topic.
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Affiliation(s)
- Fahima Chowdhury
- International Centre for Diarrheal Disease Research, Bangladesh, Dhaka, Bangladesh; Menzies Health Institute Queensland, Griffith University, Gold Coast, Australia.
| | | | - Faisal Ahmmed
- International Centre for Diarrheal Disease Research, Bangladesh, Dhaka, Bangladesh
| | - Tasnuva Ahmed
- International Centre for Diarrheal Disease Research, Bangladesh, Dhaka, Bangladesh
| | - Sophie Sy Kang
- International Vaccine Institute, Seoul, Republic of Korea
| | - Justin Im
- International Vaccine Institute, Seoul, Republic of Korea
| | - Juyeon Park
- International Vaccine Institute, Seoul, Republic of Korea; Department of Medicine, University of Cambridge, Cambridge, United Kingdom
| | | | - Md Taufiqul Islam
- International Centre for Diarrheal Disease Research, Bangladesh, Dhaka, Bangladesh
| | - Deok Ryun Kim
- International Vaccine Institute, Seoul, Republic of Korea
| | - Masuma Hoque
- International Centre for Diarrheal Disease Research, Bangladesh, Dhaka, Bangladesh
| | - Gideok Pak
- International Vaccine Institute, Seoul, Republic of Korea
| | - Farhana Khanam
- International Centre for Diarrheal Disease Research, Bangladesh, Dhaka, Bangladesh
| | - Nigel A J McMillan
- Menzies Health Institute Queensland, Griffith University, Gold Coast, Australia
| | - Xinxue Liu
- Oxford Vaccine Group, Department of Pediatrics, University of Oxford, Oxford OX3 9DU, United Kingdom
| | - Khalequ Zaman
- International Centre for Diarrheal Disease Research, Bangladesh, Dhaka, Bangladesh
| | - Ashraful Islam Khan
- International Centre for Diarrheal Disease Research, Bangladesh, Dhaka, Bangladesh
| | - Jerome H Kim
- International Vaccine Institute, Seoul, Republic of Korea
| | - Florian Marks
- International Vaccine Institute, Seoul, Republic of Korea; Department of Medicine, University of Cambridge, Cambridge, United Kingdom; University of Antananarivo, Antananarivo, Madagascar
| | - Firdausi Qadri
- International Centre for Diarrheal Disease Research, Bangladesh, Dhaka, Bangladesh
| | - John D Clemens
- International Centre for Diarrheal Disease Research, Bangladesh, Dhaka, Bangladesh; International Vaccine Institute, Seoul, Republic of Korea; UCLA Fielding School of Public Health, Los Angeles, CA 90095-1772, USA
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3
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Reidpath DD, Allotey P, Barker SF, Clasen T, French M, Leder K, Ramirez-Lovering D, Rhule ELM, Siri J. Implementing "from here to there": A case study of conceptual and practical challenges in implementation science. Soc Sci Med 2022; 301:114959. [PMID: 35398672 DOI: 10.1016/j.socscimed.2022.114959] [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: 10/21/2021] [Revised: 03/28/2022] [Accepted: 03/31/2022] [Indexed: 11/27/2022]
Abstract
There is a significant challenge in global health and development research that pivots on the difficulties of delivering (cost-)effective treatments or interventions that are scalable andtransferable across settings. That is, how does one deliver "true effects", proven treatments, into new settings? This is often addressed in pragmatic trials or implementation research in which one makes adjustments to the delivery of the treatment to ensure that it works here and there. In this critical analytical review, we argue that the approach mis-characterises the cause-effect relationship and fails to recognise the local, highly contextual nature of what it means to say an intervention "works". We use an ongoing randomised controlled trial (RCT)-an informal settlement redevelopment intervention in Indonesia and Fiji to reduce human exposure to pathogenic faecal contamination-as a vehicle for exploring the ideas and implications of identifying interventions that work in global health and development. We describe the highly contextualised features of the research and the challenges these would pose in attempts to generalise the results. In other words, we detail that which is frequently elided from most RCTs. As our critical lens, we us the work of American philosopher, Nancy Cartwright, who argued that research produces dappled regions of causal insights-lacunae against a backdrop of causal ignorance. Rather than learn about a relationship between a treatment and an outcome, we learn that in the right sort of context, a treatment reliably produces a particular outcome. Moving a treatment from here to there becomes, therefore, something of an engineering exercise to ensure the right factors (or "shields") are in place so the cause-effect is manifest. As a consequence, one cannot assume that comparative effectiveness or cost-effectiveness would be maintained.
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Affiliation(s)
- Daniel D Reidpath
- Health Systems and Population Studies Division, icddr,b, Dhaka, Bangladesh; Jeffrey Cheah School of Medicine and Health Sciences, Monash University Malaysia, Sunway, Malaysia.
| | - Pascale Allotey
- Jeffrey Cheah School of Medicine and Health Sciences, Monash University Malaysia, Sunway, Malaysia; International Institute for Global Health, United Nations University, Kuala Lumpur, Malaysia
| | - S Fiona Barker
- School of Public Health and Preventive Medicine, Faculty of Medicine, Nursing and Health Sciences, Monash University, Melbourne, Victoria, Australia
| | - Thomas Clasen
- Gangarosa Department of Environmental Health, Rollins School of Public Health, Emory University, Atlanta, GA, USA
| | - Matthew French
- Monash Sustainable Development Institute, Monash University, Melbourne, Victoria, Australia
| | - Karin Leder
- School of Public Health and Preventive Medicine, Faculty of Medicine, Nursing and Health Sciences, Monash University, Melbourne, Victoria, Australia
| | - Diego Ramirez-Lovering
- Faculty of Art, Design and Architecture, Monash University, Caulfield, Victoria, Australia
| | - Emma L M Rhule
- International Institute for Global Health, United Nations University, Kuala Lumpur, Malaysia
| | - José Siri
- International Institute for Global Health, United Nations University, Kuala Lumpur, Malaysia
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Re-evaluation of population-level protection conferred by a rotavirus vaccine using the 'fried-egg' approach in a rural setting in Bangladesh. Vaccine 2021; 39:5876-5882. [PMID: 34454788 PMCID: PMC8494114 DOI: 10.1016/j.vaccine.2021.08.048] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Revised: 06/29/2021] [Accepted: 08/12/2021] [Indexed: 11/24/2022]
Abstract
The “fried-egg” analytic approach was applied to a cluster randomized trial (CRT). Overall analysis failed to reveal rotavirus vaccine (RV) herd protection. Same approach unmasked herd protection of other enteric vaccines failed for RV.
Background Vaccine herd protection assessed in a cluster-randomized trial (CRT) may be masked by disease transmission into the cluster from outside. However, herd effects can be unmasked using a ‘fried-egg’ approach whereby the analysis, restricted to the innermost households of clusters, ‘yolk’, creates an insulating ‘egg-white’ periphery. This approach has been demonstrated to unmask vaccine herd protection in reanalyses of cholera and typhoid vaccine CRTs. We applied this approach to an earlier CRT in Bangladesh of rotavirus vaccine (RV) whose overall analysis had failed to detect herd protection. Herein we present the results of this analysis. Methods In the study area, infants in 142 villages were randomized to receive two doses of RV with routine EPI vaccines (RV villages) or only EPI vaccines (non-RV villages). We analyzed RV protection against acute rotavirus diarrhoea for the entire cluster (P100) and P75, P50, P25 clusters, representing 75%, 50% and 25% of the innermost households for each cluster, respectively. Results During 2 years of follow-up, there was evidence of 27% overall (95 %CI: 7, 43) and 42% total protection (95 %CI: 23, 56) in the P100 cluster, but it did not increase when moved in smaller yolks. There was no evidence of indirect vaccine protection in the yolks at any cluster size. Conclusion Our reanalysis of the CRT using the fried- egg approach did not detect RV herd protection. Whether these findings reflect a true inability of the RV to confer herd protection in this setting, or are due to limitations of the approach, requires further study.
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Im J, Islam MT, Ahmmed F, Kim DR, Islam Khan A, Zaman K, Ali M, Marks F, Qadri F, Kim J, Clemens JD. Can Existing Improvements of Water, Sanitation, and Hygiene (WASH) in Urban Slums Reduce the Burden of Typhoid Fever in These Settings? Clin Infect Dis 2021; 72:e720-e726. [PMID: 32964216 DOI: 10.1093/cid/ciaa1429] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Accepted: 09/17/2020] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Sustained investments in water, sanitation, and hygiene (WASH) have lagged in resource-poor settings; incremental WASH improvements may, nonetheless, prevent diseases such as typhoid in disease-endemic populations. METHODS Using prospective data from a large cohort in urban Kolkata, India, we evaluated whether baseline WASH variables predicted typhoid risk in a training subpopulation (n = 28 470). We applied a machine learning algorithm to the training subset to create a composite, dichotomous (good, not good) WASH variable based on 4 variables, and evaluated sensitivity and specificity of this variable in a validation subset (n = 28 470). We evaluated in Cox regression models whether residents of "good" WASH households experienced a lower typhoid risk after controlling for potential confounders. We constructed virtual clusters (radius 50 m) surrounding each household to evaluate whether a prevalence of good WASH practices modified the typhoid risk in central household members. RESULTS Good WASH practices were associated with protection in analyses of all households (hazard ratio [HR] = 0.57; 95% confidence interval [CI], .37-.90; P = .015). This protection was evident in persons ≥5 years old at baseline (HR = 0.47; 95% CI, .34-.93; P = .005) and was suggestive, though not statistically significant, in younger age groups (HR = 0.61; 95% CI, .27-1.38; P = .235). The level of surrounding household good WASH coverage was also associated with protection (HR = 0.988; 95% CI, .979-.996; P = .004, for each percent coverage increase). However, collinearity between household WASH and WASH coverage prevented an assessment of their independent predictive contributions. CONCLUSIONS In this typhoid-endemic setting, natural variation in household WASH was associated with typhoid risk. If replicated elsewhere, these findings suggest that WASH improvements may enhance typhoid control, short of major infrastructural investments.
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Affiliation(s)
- Justin Im
- International Vaccine Institute, Seoul, Republic of Korea
| | - Md Taufiqul Islam
- International Centre for Diarrheal Disease Research, Bangladesh, Dhaka, Bangladesh
| | - Faisal Ahmmed
- International Centre for Diarrheal Disease Research, Bangladesh, Dhaka, Bangladesh
| | - Deok Ryun Kim
- International Vaccine Institute, Seoul, Republic of Korea
| | - Ashraful Islam Khan
- International Centre for Diarrheal Disease Research, Bangladesh, Dhaka, Bangladesh
| | - Khalequ Zaman
- International Centre for Diarrheal Disease Research, Bangladesh, Dhaka, Bangladesh
| | - Mohammad Ali
- Johns Hopkins University, Baltimore, Maryland, USA
| | - Florian Marks
- International Vaccine Institute, Seoul, Republic of Korea.,Department of Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Firdausi Qadri
- International Centre for Diarrheal Disease Research, Bangladesh, Dhaka, Bangladesh
| | - Jerome Kim
- International Vaccine Institute, Seoul, Republic of Korea
| | - John D Clemens
- International Centre for Diarrheal Disease Research, Bangladesh, Dhaka, Bangladesh.,University of California Los Angeles Fielding School of Public Health, Los Angeles, California, USA
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Ali M, Qadri F, Kim DR, Islam MT, Im J, Ahmmed F, Khan AI, Zaman K, Marks F, Kim JH, Clemens JD. Effectiveness of a killed whole-cell oral cholera vaccine in Bangladesh: further follow-up of a cluster-randomised trial. THE LANCET. INFECTIOUS DISEASES 2021; 21:1407-1414. [PMID: 34146473 DOI: 10.1016/s1473-3099(20)30781-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 08/24/2020] [Accepted: 09/24/2020] [Indexed: 11/19/2022]
Abstract
BACKGROUND Killed whole-cell oral cholera vaccines (OCVs) are widely used for prevention of cholera in developing countries. However, few studies have evaluated the protection conferred by internationally recommended OCVs for durations beyond 2 years of follow-up. METHODS In this study, we followed up the participants of a cluster-randomised controlled trial for 2 years after the end of the original trial. Originally, we had randomised 90 geographical clusters in Dhaka slums in Bangladesh in equal numbers (1:1:1) to a two-dose regimen of OCV alone (targeted to people aged 1 year or older), a two-dose regimen of OCV plus a water-sanitation-hygiene (WASH) intervention, or no intervention. There was no masking of group assignment. The WASH intervention conferred little additional protection to OCV and was discontinued at 2 years of follow-up. Surveillance for severe cholera was continued for 4 years. Because of the short duration and effect of the WASH intervention, we combined the two OCV intervention groups. The primary outcomes were OCV overall protection (protection of all members of the intervention clusters) and total protection (protection of individuals who got vaccinated in the intervention clusters) against severe cholera, which we assessed by multivariable survival models appropriate for cluster-randomised trials. This trial is registered on ClinicalTrials.gov, NCT01339845. FINDINGS The study was done between April 17, 2011, and Nov 1, 2015. 268 896 participants were present at the time of the first dose, with 188 206 in the intervention group and 80 690 in the control group. OCV coverage of the two groups receiving OCV was 66% (123 659 of 187 214 participants). During 4 years of follow-up, 441 first episodes of severe cholera were detected (243 episodes in the vaccinated groups and as 198 episodes in the unvaccinated group). Overall OCV protection was 36% (95% CI 19 to 49%) and total OCV protection was 46% (95% CI 32 to 58). Cumulative total vaccine protection was notably lower for people vaccinated before the age of 5 years (24%; -30 to 56) than for people vaccinated at age 5 years or older (49%; 35 to 60), although the differences in protection for the two age groups were not significant (p=0·3308). Total vaccine protection dropped notably (p=0·0115) after 3 years in children vaccinated at 1-4 years of age. INTERPRETATION These findings provide further evidence of long-term effectiveness of killed whole-cell OCV, and therefore further support for the use of killed whole-cell OCVs to control endemic cholera, but indicate that protection is shorter-lived in children vaccinated before the age of 5 years than in people vaccinated at the age of 5 years or older. FUNDING Bill & Melinda Gates Foundation. TRANSLATION For the Bengali translation of the abstract see Supplementary Materials section.
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Affiliation(s)
- Mohammad Ali
- Johns Hopkins Bloomberg School of Public Health, Baltimore, MA, USA
| | - Firdausi Qadri
- International Centre for Diarrheal Disease Research, Bangladesh, Dhaka, Bangladesh.
| | | | - Md Taufiqul Islam
- International Centre for Diarrheal Disease Research, Bangladesh, Dhaka, Bangladesh
| | - Justin Im
- International Vaccine Institute, Seoul, South Korea
| | - Faisal Ahmmed
- International Centre for Diarrheal Disease Research, Bangladesh, Dhaka, Bangladesh
| | - Ashraful Islam Khan
- International Centre for Diarrheal Disease Research, Bangladesh, Dhaka, Bangladesh
| | - K Zaman
- International Centre for Diarrheal Disease Research, Bangladesh, Dhaka, Bangladesh
| | - Florian Marks
- International Vaccine Institute, Seoul, South Korea; Department of Medicine, University of Cambridge, Cambridge, UK
| | - Jerome H Kim
- International Vaccine Institute, Seoul, South Korea
| | - John D Clemens
- International Centre for Diarrheal Disease Research, Bangladesh, Dhaka, Bangladesh; UCLA Fielding School of Public Health, Los Angeles, CA, USA
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Clemente-Suárez VJ, Hormeño-Holgado A, Jiménez M, Benitez-Agudelo JC, Navarro-Jiménez E, Perez-Palencia N, Maestre-Serrano R, Laborde-Cárdenas CC, Tornero-Aguilera JF. Dynamics of Population Immunity Due to the Herd Effect in the COVID-19 Pandemic. Vaccines (Basel) 2020; 8:E236. [PMID: 32438622 PMCID: PMC7349986 DOI: 10.3390/vaccines8020236] [Citation(s) in RCA: 58] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Revised: 05/14/2020] [Accepted: 05/15/2020] [Indexed: 02/07/2023] Open
Abstract
The novel Coronavirus 2 Severe Acute Respiratory Syndrome (SARS-Cov-2) has led to the Coronavirus Disease 2019 (COVID-19) pandemic, which has surprised health authorities around the world, quickly producing a global health crisis. Different actions to cope with this situation are being developed, including confinement, different treatments to improve symptoms, and the creation of the first vaccines. In epidemiology, herd immunity is presented as an area that could also solve this new global threat. In this review, we present the basis of herd immunology, the dynamics of infection transmission that induces specific immunity, and how the application of immunoepidemiology and herd immunology could be used to control the actual COVID-19 pandemic, along with a discussion of its effectiveness, limitations, and applications.
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Affiliation(s)
- Vicente Javier Clemente-Suárez
- Faculty of Sports Sciences, Universidad Europea de Madrid, 28670 Madrid, Spain;
- Grupo de Investigación en Cultura, Educación y Sociedad, Universidad de la Costa, Barranquilla 080002, Colombia
- Studies Centre in Applied Combat (CESCA), Toledo 45007, Spain;
| | | | - Manuel Jiménez
- Departamento de Didáctica de la Educación Física y Salud, Universidad Internacional de La Rioja, Logroño 26006, Spain;
| | | | - Eduardo Navarro-Jiménez
- Facultad de Ciencias de la Salud, Universidad Simón Bolívar, Barranquilla 080005, Colombia; (E.N.-J.); (R.M.-S.)
| | | | - Ronald Maestre-Serrano
- Facultad de Ciencias de la Salud, Universidad Simón Bolívar, Barranquilla 080005, Colombia; (E.N.-J.); (R.M.-S.)
| | | | - Jose Francisco Tornero-Aguilera
- Faculty of Sports Sciences, Universidad Europea de Madrid, 28670 Madrid, Spain;
- Studies Centre in Applied Combat (CESCA), Toledo 45007, Spain;
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Ali M, Sur D, Kanungo S, Qadri F, Kim DR, Islam T, Im J, Ahmmed F, Chon Y, Khan AI, Zaman K, Marks F, Dutta S, Bhattacharya SK, Clemens JD. Re-evaluating herd protection by Vi typhoid vaccine in a cluster randomized trial. Int Health 2020; 12:36-42. [PMID: 31608962 PMCID: PMC6964216 DOI: 10.1093/inthealth/ihz069] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Revised: 07/04/2019] [Accepted: 07/11/2019] [Indexed: 01/14/2023] Open
Abstract
Background In a cluster randomized trial (CRT) of a Vi polysaccharide vaccine against typhoid in the slums of Kolkata we found evidence of vaccine herd protection. However, transmission of typhoid into clusters from the outside likely occurred in this densely populated setting, which could have diminished our estimates of vaccine herd protection. Methods Eighty clusters (40 in each arm) were randomised to receive a single dose of either Vi or inactivated hepatitis A vaccine. We analysed protection for the entire cluster and for subclusters consisting of residents of the innermost households. Results During 2 y of follow-up, total protection was 61% (95% CI 41 to 75), overall protection was 57% (95% CI 37 to 71) and indirect protection was 44% (95% CI 2 to 69). Analyses of the innermost 75% and 50% of households of the clusters showed similar findings. However, in the innermost 25% of households of the clusters, total protection was 82% (95% CI 48 to 94) and overall protection was 66% (95% CI 27 to 84). There was not a sufficient sample size to demonstrate such a trend for indirect protection in these innermost households. Conclusions The findings suggest that analyses of the entire cluster may have led to underestimation of herd protection against typhoid by Vi vaccine and that restriction of the analyses to the inner subclusters may have led to a more accurate estimation of vaccine herd effects.
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Affiliation(s)
- Mohammad Ali
- Johns Hopkins Bloomberg School of Public Health, 615, N Wolfe Street, Baltimore, MD-21205, USA
| | - Dipika Sur
- National Institute of Cholera and Enteric Diseases, P-33 CIT Road, Scheme XM, Beliaghata, Kolkata, India
| | - Suman Kanungo
- National Institute of Cholera and Enteric Diseases, P-33 CIT Road, Scheme XM, Beliaghata, Kolkata, India
| | - Firdausi Qadri
- International Centre for Diarrhoeal Disease Research, Bangladesh, 68 Shaheed Tajuddin Ahmed Sarani Mohakhali, Dhaka 1212, Bangladesh
| | - Deok Ryun Kim
- International Vaccine Institute, SNU Research Park, 1 Gwanak-ro, Gwanak-gu, Seoul, Republic of Korea
| | - Taufiqul Islam
- International Centre for Diarrhoeal Disease Research, Bangladesh, 68 Shaheed Tajuddin Ahmed Sarani Mohakhali, Dhaka 1212, Bangladesh
| | - Justin Im
- International Vaccine Institute, SNU Research Park, 1 Gwanak-ro, Gwanak-gu, Seoul, Republic of Korea
| | - Faisal Ahmmed
- International Centre for Diarrhoeal Disease Research, Bangladesh, 68 Shaheed Tajuddin Ahmed Sarani Mohakhali, Dhaka 1212, Bangladesh
| | - Yun Chon
- International Vaccine Institute, SNU Research Park, 1 Gwanak-ro, Gwanak-gu, Seoul, Republic of Korea
| | - Ashraful Islam Khan
- International Centre for Diarrhoeal Disease Research, Bangladesh, 68 Shaheed Tajuddin Ahmed Sarani Mohakhali, Dhaka 1212, Bangladesh
| | - K Zaman
- International Centre for Diarrhoeal Disease Research, Bangladesh, 68 Shaheed Tajuddin Ahmed Sarani Mohakhali, Dhaka 1212, Bangladesh
| | - Florian Marks
- International Vaccine Institute, SNU Research Park, 1 Gwanak-ro, Gwanak-gu, Seoul, Republic of Korea.,Department of Medicine, University of Cambridge, Cambridge, UK
| | - Shanta Dutta
- National Institute of Cholera and Enteric Diseases, P-33 CIT Road, Scheme XM, Beliaghata, Kolkata, India
| | - Sujit K Bhattacharya
- National Institute of Cholera and Enteric Diseases, P-33 CIT Road, Scheme XM, Beliaghata, Kolkata, India
| | - John D Clemens
- International Centre for Diarrhoeal Disease Research, Bangladesh, 68 Shaheed Tajuddin Ahmed Sarani Mohakhali, Dhaka 1212, Bangladesh.,UCLA Fielding School of Public Health, Los Angeles, CA 90095-1772, USA
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Ali M, Clemens J. Assessing Vaccine Herd Protection by Killed Whole-Cell Oral Cholera Vaccines Using Different Study Designs. Front Public Health 2019; 7:211. [PMID: 31417890 PMCID: PMC6685418 DOI: 10.3389/fpubh.2019.00211] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2019] [Accepted: 07/16/2019] [Indexed: 11/25/2022] Open
Abstract
The population level effectiveness of a vaccine may arise as the result of direct protection of vaccinees and vaccine herd protection, which may protect non-vaccinees, vaccinees, or both. Indirect, total, enhanced, and overall vaccine protection are measures of vaccine herd protection. The level of population level effectiveness induced by a vaccine is driven by several factors, including known vaccine-induced protective efficacy, the magnitude, and distribution of vaccine coverage at a point in time and the extent to which different groups mix with one another in the community. Data on vaccine herd protection are valuable in understanding the importance and cost-effectiveness in deploying the e vaccine in public health program. Killed whole-cell (WC) oral cholera vaccines (OCVs) have been evaluated for herd protection in various study settings, leveraging geographic information system (GIS) tools for the analyses. This article provides a brief description of the herd protective effects of killed WC OCVs measured using various study deigns that include (a) individually randomized, controlled clinical trials, (b) cluster randomized clinical trials, (c) observational cohort studies, and (d) observational case-control studies. In all of the study designs, significant herd protection was observed in unvaccinated persons as well as in the community as a whole. The findings of these studies suggest that using killed WC OCV as a public health tool for controlling cholera is impactful and cost-effective.
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Affiliation(s)
- Mohammad Ali
- Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, United States
| | - John Clemens
- International Centre for Diarrhoeal Disease Research, Dhaka, Bangladesh
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