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Zinsou JF, Diemert DJ, Dejon-Agobé JC, Adégbité BR, Honkpehedji YJ, Vodonou KG, Bikangui R, Edoa JR, Massinga Loembe M, Li G, Yazdanbakhsh M, Bottazzi ME, van Leeuwen R, Kremsner PG, Hotez PJ, Bethony JM, Grobusch MP, Adegnika AA. Safety and immunogenicity of the co-administered Na-APR-1 and Na-GST-1 hookworm vaccines in school-aged children in Gabon: a randomised, controlled, observer-blind, phase 1, dose-escalation trial. THE LANCET. INFECTIOUS DISEASES 2024; 24:760-774. [PMID: 38513684 DOI: 10.1016/s1473-3099(24)00104-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/01/2024] [Revised: 02/07/2024] [Accepted: 02/08/2024] [Indexed: 03/23/2024]
Abstract
BACKGROUND A human hookworm vaccine is being developed to protect children against iron deficiency and anaemia associated with chronic infection with hookworms. Necator americanus aspartic protease-1 (Na-APR-1) and N americanus glutathione S-transferase-1 (Na-GST-1) are components of the blood digestion pathway critical to hookworm survival in the host. Recombinant Na-GST-1 and catalytically inactive Na-APR-1 (Na-APR-1[M74]) adsorbed to Alhydrogel were safe and immunogenic when delivered separately or co-administered to adults in phase 1 trials in non-endemic and endemic areas. We aimed to investigate the safety and immunogenicity of these antigens in healthy children in a hookworm-endemic area. METHODS This was a randomised, controlled, observer-blind, phase 1, dose-escalation trial, conducted in a clinical research centre, in 60 children aged six to ten years in Lambaréné, a hookworm-endemic region of Gabon. Healthy children (determined by clinical examination and safety laboratory testing) were randomised 4:1 to receive co-administered Na-GST-1 on Alhydrogel plus Na-APR-1(M74) on Alhydrogel and glucopyranosyl lipid A in aqueous formulation (GLA-AF), or co-administered ENGERIX-B hepatitis B vaccine (HBV) and saline placebo, injected into the deltoid of each arm. Allocation to vaccine groups was observer-masked. In each vaccine group, children were randomised 1:1 to receive intramuscular injections into each deltoid on two vaccine schedules, one at months 0, 2, and 4 or at months 0, 2, and 6. 10 μg, 30 μg, and 100 μg of each antigen were administered in the first, second, and third cohorts, respectively. The intention-to-treat population was used for safety analyses; while for immunogenicity analyses, the per-protocol population was used (children who received all scheduled vaccinations). The primary outcome was to evaluate the vaccines' safety and reactogenicity in healthy children aged between six and ten years. The secondary outcome was to measure antigen-specific serum IgG antibody levels at pre-vaccination and post-vaccination timepoints by qualified ELISAs. The trial is registered with ClinicalTrials.gov, NCT02839161, and is completed. FINDINGS Between Jan 23 and Oct 3, 2017, 137 children were screened, of whom 76 were eligible for this trial. 60 children were recruited, and allocated to either 10 μg of the co-administered antigens (n=8 for each injection schedule), 30 μg (n=8 for each schedule), 100 μg (n=8 for each schedule), or HBV and placebo (n=6 for each schedule) in three sequential cohorts. Co-administration of the vaccines was well tolerated; the most frequent solicited adverse events were mild-to-moderate injection-site pain, observed in up to 12 (75%) of 16 participants per vaccine group, and mild headache (12 [25%] of 48) and fever (11 [23%] of 48). No vaccine-related serious adverse events were observed. Significant anti-Na-APR-1(M74) and anti-Na-GST-1 IgG levels were induced in a dose-dependent manner, with peaks seen 14 days after the third vaccinations, regardless of dose (for Na-APR-1[M74], geometric mean levels [GML]=2295·97 arbitrary units [AU] and 726·89 AU, while for Na-GST-1, GMLs=331·2 AU and 21·4 AU for the month 0, 2, and 6 and month 0, 2, and 4 schedules, respectively). The month 0, 2, and 6 schedule induced significantly higher IgG responses to both antigens (p=0·01 and p=0·04 for Na-APR-1[M74] and Na-GST-1, respectively). INTERPRETATION Co-administration of recombinant Na-APR-1(M74) and Na-GST-1 to school-aged Gabonese children was well tolerated and induced significant IgG responses. These results justify further evaluation of this antigen combination in proof-of-concept controlled-infection and efficacy studies in hookworm-endemic areas. FUNDING European Union Seventh Framework Programme.
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Affiliation(s)
- Jeannot F Zinsou
- Centre de Recherches Médicales de Lambaréné (CERMEL), Lambaréné, Gabon; Institut für Tropenmedizin, Universität Tübingen and German Center for Infection Research, Tübingen, Germany; Fondation pour la Recherche Scientifique (FORS), Cotonou, Benin
| | - David J Diemert
- Department of Medicine, School of Medicine and Health Sciences, The George Washington University, Washington DC, USA; Department of Microbiology, Immunology and Tropical Medicine, School of Medicine and Health Sciences, The George Washington University, Washington DC, USA.
| | | | - Bayodé R Adégbité
- Centre de Recherches Médicales de Lambaréné (CERMEL), Lambaréné, Gabon; Institut für Tropenmedizin, Universität Tübingen and German Center for Infection Research, Tübingen, Germany; Center of Tropical Medicine and Travel Medicine, Department of Infectious Diseases, Division of Internal Medicine, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands
| | - Yabo Josiane Honkpehedji
- Centre de Recherches Médicales de Lambaréné (CERMEL), Lambaréné, Gabon; Fondation pour la Recherche Scientifique (FORS), Cotonou, Benin; Department of Parasitology, Leiden University Medical Center, Leiden, Netherlands
| | - Kafui G Vodonou
- Centre de Recherches Médicales de Lambaréné (CERMEL), Lambaréné, Gabon
| | - Rodrigue Bikangui
- Centre de Recherches Médicales de Lambaréné (CERMEL), Lambaréné, Gabon
| | - Jean Ronald Edoa
- Centre de Recherches Médicales de Lambaréné (CERMEL), Lambaréné, Gabon
| | | | - Guangzhao Li
- Department of Microbiology, Immunology and Tropical Medicine, School of Medicine and Health Sciences, The George Washington University, Washington DC, USA
| | - Maria Yazdanbakhsh
- Department of Parasitology, Leiden University Medical Center, Leiden, Netherlands
| | - Maria Elena Bottazzi
- Departments of Pediatrics, Division of Pediatric Tropical Medicine, and Molecular Virology and Microbiology, Texas Children's Hospital Center for Vaccine Development, National School of Tropical Medicine, Baylor College of Medicine, Houston, TX, USA
| | - Remko van Leeuwen
- Amsterdam Institute for Global Development (AIGHD), Amsterdam, Netherlands
| | - Peter G Kremsner
- Centre de Recherches Médicales de Lambaréné (CERMEL), Lambaréné, Gabon; Institut für Tropenmedizin, Universität Tübingen and German Center for Infection Research, Tübingen, Germany
| | - Peter J Hotez
- Departments of Pediatrics, Division of Pediatric Tropical Medicine, and Molecular Virology and Microbiology, Texas Children's Hospital Center for Vaccine Development, National School of Tropical Medicine, Baylor College of Medicine, Houston, TX, USA
| | - Jeffrey M Bethony
- Department of Microbiology, Immunology and Tropical Medicine, School of Medicine and Health Sciences, The George Washington University, Washington DC, USA
| | - Martin P Grobusch
- Centre de Recherches Médicales de Lambaréné (CERMEL), Lambaréné, Gabon; Institut für Tropenmedizin, Universität Tübingen and German Center for Infection Research, Tübingen, Germany; Center of Tropical Medicine and Travel Medicine, Department of Infectious Diseases, Division of Internal Medicine, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands; Department of Parasitology, Leiden University Medical Center, Leiden, Netherlands
| | - Ayola A Adegnika
- Centre de Recherches Médicales de Lambaréné (CERMEL), Lambaréné, Gabon; Institut für Tropenmedizin, Universität Tübingen and German Center for Infection Research, Tübingen, Germany; Fondation pour la Recherche Scientifique (FORS), Cotonou, Benin; Department of Parasitology, Leiden University Medical Center, Leiden, Netherlands
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Hoogerwerf MA, Coffeng LE, Brienen EAT, Janse JJ, Langenberg MCC, Kruize YCM, Gootjes C, Manurung MD, Dekker M, Becker L, Erkens MAA, van der Beek MT, Ganesh MS, Feijt C, Winkel BMF, Westra IM, Meij P, Loukas A, Visser LG, de Vlas SJ, Yazdanbakhsh M, van Lieshout L, Roestenberg M. New Insights Into the Kinetics and Variability of Egg Excretion in Controlled Human Hookworm Infections. J Infect Dis 2020; 220:1044-1048. [PMID: 31077279 DOI: 10.1093/infdis/jiz218] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Accepted: 05/10/2019] [Indexed: 12/29/2022] Open
Abstract
Four healthy volunteers were infected with 50 Necator americanus infective larvae (L3) in a controlled human hookworm infection trial and followed for 52 weeks. The kinetics of fecal egg counts in volunteers was assessed with Bayesian multilevel analysis, which revealed an increase between weeks 7 and 13, followed by an egg density plateau of about 1000 eggs/g of feces. Variation in egg counts was minimal between same-day measurements but varied considerably between days, particularly during the plateau phase. These analyses pave the way for the controlled human hookworm model to accelerate drug and vaccine efficacy studies.
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Affiliation(s)
| | - Luc E Coffeng
- Department of Public Health, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, the Netherlands
| | - Eric A T Brienen
- Department of Parasitology, Leiden University Medical Center, Leiden
| | | | | | - Yvonne C M Kruize
- Department of Parasitology, Leiden University Medical Center, Leiden
| | - Chelsea Gootjes
- Department of Parasitology, Leiden University Medical Center, Leiden
| | | | - Mark Dekker
- Department of Parasitology, Leiden University Medical Center, Leiden
| | - Luke Becker
- Centre for Biodiscovery and Molecular Development of Therapeutics, Australian Institute of Tropical Health and Medicine, James Cook University, Cairns
| | | | | | - Munisha S Ganesh
- Department of Parasitology, Leiden University Medical Center, Leiden
| | - Carola Feijt
- Department of Parasitology, Leiden University Medical Center, Leiden
| | | | - Inge M Westra
- Department of Clinical Pharmacy and Toxicology, Leiden University Medical Center, Leiden
| | - Pauline Meij
- Department of Clinical Pharmacy and Toxicology, Leiden University Medical Center, Leiden
| | - Alex Loukas
- Centre for Biodiscovery and Molecular Development of Therapeutics, Australian Institute of Tropical Health and Medicine, James Cook University, Cairns
| | - Leo G Visser
- Department of Infectious Diseases, Leiden University Medical Center, Leiden
| | - Sake J de Vlas
- Department of Public Health, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, the Netherlands
| | | | | | - Meta Roestenberg
- Department of Parasitology, Leiden University Medical Center, Leiden.,Department of Infectious Diseases, Leiden University Medical Center, Leiden
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Diemert D, Campbell D, Brelsford J, Leasure C, Li G, Peng J, Zumer M, Younes N, Bottazzi ME, Mejia R, Pritchard DI, Hawdon JM, Bethony JM. Controlled Human Hookworm Infection: Accelerating Human Hookworm Vaccine Development. Open Forum Infect Dis 2018; 5:ofy083. [PMID: 29780848 PMCID: PMC5952933 DOI: 10.1093/ofid/ofy083] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Accepted: 04/16/2018] [Indexed: 11/14/2022] Open
Abstract
Background Controlled human hookworm infection (CHHI) is a central component of a proposed hookworm vaccination-challenge model (HVCM) to test the efficacy of candidate vaccines. Critical to CHHI is the manufacture of Necator americanus infective larvae (NaL3) according to current Good Manufacturing Practice (cGMP) and the determination of an inoculum of NaL3 that is safe and reliably induces patent infection. Methods cGMP-grade NaL3 were produced for a phase 1 trial in 20 healthy, hookworm-naïve adults in the United States, who received either 25 or 50 NaL3. Participants were monitored for 12–18 weeks postinfection for safety, tolerability, and patency of N. americanus infection. Results Both NaL3 doses were well tolerated. Early manifestations of infection included pruritus, pain, and papulovesicular rash at the application site. Gastrointestinal symptoms and eosinophilia appeared after week 4 postinfection. The 50 NaL3 inoculum induced patent N. americanus infection in 90% of this dose group. Conclusions The inoculum of 50 NaL3 was well tolerated and consistently induced patent N. americanus infection suitable for future HVCM trials. Clinical Trials Registration NCT01940757.
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Affiliation(s)
- David Diemert
- Department of Microbiology, Immunology and Tropical Medicine, Washington DC.,Department of Medicine, Washington DC
| | - Doreen Campbell
- Department of Microbiology, Immunology and Tropical Medicine, Washington DC
| | - Jill Brelsford
- Department of Microbiology, Immunology and Tropical Medicine, Washington DC
| | - Caitlyn Leasure
- Department of Microbiology, Immunology and Tropical Medicine, Washington DC
| | - Guangzhao Li
- Department of Microbiology, Immunology and Tropical Medicine, Washington DC
| | - Jin Peng
- Department of Microbiology, Immunology and Tropical Medicine, Washington DC
| | | | - Naji Younes
- Milken Institute School of Public Health, The George Washington University, Washington DC
| | - Maria Elena Bottazzi
- Department of Pediatrics, Section of Pediatric Tropical Medicine, Texas Children's Hospital Center for Vaccine Development, National School of Tropical Medicine, Baylor College of Medicine, Houston, Texas
| | - Rojelio Mejia
- Department of Pediatrics, Section of Pediatric Tropical Medicine, Texas Children's Hospital Center for Vaccine Development, National School of Tropical Medicine, Baylor College of Medicine, Houston, Texas
| | - David I Pritchard
- Department of Pharmacy, University of Nottingham, Nottingham, United Kingdom
| | - John M Hawdon
- Department of Microbiology, Immunology and Tropical Medicine, Washington DC
| | - Jeffrey M Bethony
- Department of Microbiology, Immunology and Tropical Medicine, Washington DC
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Silver ZA, Kaliappan SP, Samuel P, Venugopal S, Kang G, Sarkar R, Ajjampur SSR. Geographical distribution of soil transmitted helminths and the effects of community type in South Asia and South East Asia - A systematic review. PLoS Negl Trop Dis 2018; 12:e0006153. [PMID: 29346440 PMCID: PMC5773013 DOI: 10.1371/journal.pntd.0006153] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Accepted: 12/05/2017] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND Soil-transmitted helminth (STH) infections are among the most prevalent neglected tropical diseases (NTD) worldwide. Since the publication of the WHO road map to combat NTD in 2012, there has been a renewed commitment to control STH. In this study, we analysed the geographical distribution and effect of community type on prevalence of hookworm, Trichuris and Ascaris in south Asia and south east Asia. METHODOLOGY We conducted a systematic review of open-access literature published in PubMed Central and the Global Atlas of Helminth Infection. A total of 4182 articles were available and after applying selection criteria, 174 studies from the region were retained for analysis. PRINCIPAL FINDINGS Ascaris was the commonest STH identified with an overall prevalence of 18% (95% CI, 14-23%) followed by Trichuris (14%, 9-19%) and hookworm (12%, 9-15%). Hookworm prevalence was highest in Laos, Vietnam and Cambodia. We found a geographical overlap in countries with high prevalence rates for Trichuris and Ascaris (Malaysia, Philippines, Myanmar, Vietnam and Bangladesh). When the effect of community type was examined, prevalence rates of hookworm was comparable in rural (19%, 14-24%) and tribal communities (14%, 10-19%). Tribal communities, however, showed higher prevalence of Trichuris (38%, 18-63%) and Ascaris (32%, 23-43%) than rural communities (13%, 9-20% and 14%, 9-20% respectively). Considerable between and within country heterogeneity in the distribution of STH (I2 >90%) was also noted. When available data from school aged children (SAC) were analysed, prevalence of Ascaris (25% 16-31%) and Trichuris (22%, 14-34%) were higher than among the general population while that of hookworm (10%, 7-16%) was comparable. CONCLUSIONS/SIGNIFICANCE Our analysis showed significant variation in prevalence rates between and within countries in the region. Highlighting the importance of community type in prevalence and species mix, we showed that tribal and rural communities had higher hookworm infections than urban communities and for ascariasis and trichuriasis, tribal populations had higher levels of infection than rural populations. We also found a higher prevalence of ascariasis and trichuriasis in SAC compared to the general population but comparable levels of hookworm infections. These key findings need to be taken into account in planning future MDA and other interventions.
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Affiliation(s)
- Zachary A. Silver
- Division of Geographic Medicine and Infectious Diseases, Tufts University School of Medicine, Boston, MA, United States of America
| | | | - Prasanna Samuel
- Division of Gastrointestinal Sciences, Christian Medical College, Vellore, India
- Department of Biostatistics, Christian Medical College, Vellore, India
| | - Srinivasan Venugopal
- Division of Gastrointestinal Sciences, Christian Medical College, Vellore, India
| | - Gagandeep Kang
- Division of Gastrointestinal Sciences, Christian Medical College, Vellore, India
| | - Rajiv Sarkar
- Division of Gastrointestinal Sciences, Christian Medical College, Vellore, India
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Camacho A, Eggo RM, Goeyvaerts N, Vandebosch A, Mogg R, Funk S, Kucharski AJ, Watson CH, Vangeneugden T, Edmunds WJ. Real-time dynamic modelling for the design of a cluster-randomized phase 3 Ebola vaccine trial in Sierra Leone. Vaccine 2016; 35:544-551. [PMID: 28024952 DOI: 10.1016/j.vaccine.2016.12.019] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Revised: 11/17/2016] [Accepted: 12/12/2016] [Indexed: 01/03/2023]
Abstract
BACKGROUND Declining incidence and spatial heterogeneity complicated the design of phase 3 Ebola vaccine trials during the tail of the 2013-16 Ebola virus disease (EVD) epidemic in West Africa. Mathematical models can provide forecasts of expected incidence through time and can account for both vaccine efficacy in participants and effectiveness in populations. Determining expected disease incidence was critical to calculating power and determining trial sample size. METHODS In real-time, we fitted, forecasted, and simulated a proposed phase 3 cluster-randomized vaccine trial for a prime-boost EVD vaccine in three candidate regions in Sierra Leone. The aim was to forecast trial feasibility in these areas through time and guide study design planning. RESULTS EVD incidence was highly variable during the epidemic, especially in the declining phase. Delays in trial start date were expected to greatly reduce the ability to discern an effect, particularly as a trial with an effective vaccine would cause the epidemic to go extinct more quickly in the vaccine arm. Real-time updates of the model allowed decision-makers to determine how trial feasibility changed with time. CONCLUSIONS This analysis was useful for vaccine trial planning because we simulated effectiveness as well as efficacy, which is possible with a dynamic transmission model. It contributed to decisions on choice of trial location and feasibility of the trial. Transmission models should be utilised as early as possible in the design process to provide mechanistic estimates of expected incidence, with which decisions about sample size, location, timing, and feasibility can be determined.
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Affiliation(s)
- A Camacho
- Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, Keppel Street, London WC1E 7HT, UK
| | - R M Eggo
- Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, Keppel Street, London WC1E 7HT, UK.
| | | | | | - R Mogg
- Janssen Research & Development, LLC, Spring House, PA, USA
| | - S Funk
- Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, Keppel Street, London WC1E 7HT, UK
| | - A J Kucharski
- Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, Keppel Street, London WC1E 7HT, UK
| | - C H Watson
- Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, Keppel Street, London WC1E 7HT, UK
| | | | - W J Edmunds
- Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, Keppel Street, London WC1E 7HT, UK
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Abstract
The 2000 Millennium Development Goals helped stimulate the development of life-saving childhood vaccines for pneumococcal and rotavirus infections while greatly expanding coverage of existing vaccines. However, there remains an urgent need to develop new vaccines for HIV/AIDS, malaria, and tuberculosis, as well as for respiratory syncytial virus and those chronic and debilitating (mostly parasitic) infections known as neglected tropical diseases (NTDs). The NTDs represent the most common diseases of people living in extreme poverty and are the subject of this review. The development of NTD vaccines, including those for hookworm infection, schistosomiasis, leishmaniasis, and Chagas disease, is being led by nonprofit product development partnerships (PDPs) working in consortia of academic and industrial partners, including vaccine manufacturers in developing countries. NTD vaccines face unique challenges with respect to their product development and manufacture, as well as their preclinical and clinical testing. We emphasize global efforts to accelerate the development of NTD vaccines and some of the hurdles to ensuring their availability to the world's poorest people.
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Affiliation(s)
- Peter J Hotez
- Department of Pediatrics, National School of Tropical Medicine, Baylor College of Medicine, Houston, Texas 77030; .,Department of Molecular Virology & Microbiology, National School of Tropical Medicine, Baylor College of Medicine, Houston, Texas 77030; , .,Sabin Vaccine Institute and Texas Children's Hospital Center for Vaccine Development, Houston, Texas 77030.,Sabin Vaccine Institute, Washington, DC and Houston, Texas.,Baker Institute, Rice University, Houston, Texas 77030.,Department of Biology, Baylor University, Waco, Texas 76706
| | - Maria Elena Bottazzi
- Department of Pediatrics, National School of Tropical Medicine, Baylor College of Medicine, Houston, Texas 77030; .,Department of Molecular Virology & Microbiology, National School of Tropical Medicine, Baylor College of Medicine, Houston, Texas 77030; , .,Sabin Vaccine Institute and Texas Children's Hospital Center for Vaccine Development, Houston, Texas 77030.,Sabin Vaccine Institute, Washington, DC and Houston, Texas.,Department of Biology, Baylor University, Waco, Texas 76706
| | - Ulrich Strych
- Department of Pediatrics, National School of Tropical Medicine, Baylor College of Medicine, Houston, Texas 77030; .,Sabin Vaccine Institute and Texas Children's Hospital Center for Vaccine Development, Houston, Texas 77030
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Sample size calculations for skewed distributions. BMC Med Res Methodol 2015; 15:28. [PMID: 25886883 PMCID: PMC4423589 DOI: 10.1186/s12874-015-0023-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2014] [Accepted: 03/24/2015] [Indexed: 11/10/2022] Open
Abstract
Background Sample size calculations should correspond to the intended method of analysis. Nevertheless, for non-normal distributions, they are often done on the basis of normal approximations, even when the data are to be analysed using generalized linear models (GLMs). Methods For the case of comparison of two means, we use GLM theory to derive sample size formulae, with particular cases being the negative binomial, Poisson, binomial, and gamma families. By simulation we estimate the performance of normal approximations, which, via the identity link, are special cases of our approach, and for common link functions such as the log. The negative binomial and gamma scenarios are motivated by examples in hookworm vaccine trials and insecticide-treated materials, respectively. Results Calculations on the link function (log) scale work well for the negative binomial and gamma scenarios examined and are often superior to the normal approximations. However, they have little advantage for the Poisson and binomial distributions. Conclusions The proposed method is suitable for sample size calculations for comparisons of means of highly skewed outcome variables. Electronic supplementary material The online version of this article (doi:10.1186/s12874-015-0023-0) contains supplementary material, which is available to authorized users.
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8
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New concepts in diagnostics for infectious diarrhea. Mucosal Immunol 2013; 6:876-85. [PMID: 23881355 DOI: 10.1038/mi.2013.50] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2013] [Accepted: 06/11/2013] [Indexed: 02/04/2023]
Abstract
Conventional approaches to the diagnosis of infectious diarrhea must include several modalities to detect an array of potential viruses, bacteria, and parasites. We will provide a general overview of the wide range of diagnostic modalities available for enteropathogens, briefly discuss some of the limitations of conventional methods, and then focus on new molecular methods, including real-time PCR and next-generation sequencing. In particular, we will discuss quantitation of pathogen load with these techniques. We will then describe examples whereby novel diagnostics may help illuminate the etiology of infectious diarrhea, where they may not, and how they may benefit studies of immunity to enteric infections.
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Abstract
OBJECTIVE To review methods for the statistical analysis of parasite and other skewed count data. METHODS Statistical methods for skewed count data are described and compared, with reference to a 10-year period of Tropical Medicine and International Health (TMIH). Two parasitological datasets are used for illustration. RESULTS The review of TMIH found 90 articles, of which 89 used descriptive methods and 60 used inferential analysis. A lack of clarity is noted in identifying the measures of location, in particular the Williams and geometric means. The different measures are compared, emphasising the legitimacy of the arithmetic mean for the skewed data. In the published articles, the t test and related methods were often used on untransformed data, which is likely to be invalid. Several approaches to inferential analysis are described, emphasising (1) non-parametric methods, while noting that they are not simply comparisons of medians, and (2) generalised linear modelling, in particular with the negative binomial distribution. Additional methods, such as the bootstrap, with potential for greater use are described. CONCLUSIONS Clarity is recommended when describing transformations and measures of location. It is suggested that non-parametric methods and generalised linear models are likely to be sufficient for most analyses.
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Affiliation(s)
- Neal Alexander
- London School of Hygiene and Tropical Medicine, London, UK.
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Cundill B, Alexander N, Bethony JM, Diemert D, Pullan RL, Brooker S. Rates and intensity of re-infection with human helminths after treatment and the influence of individual, household, and environmental factors in a Brazilian community. Parasitology 2011; 138:1406-16. [PMID: 21819640 PMCID: PMC3827741 DOI: 10.1017/s0031182011001132] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
This study quantifies the rate and intensity of re-infection with human hookworm and Schistosoma mansoni infection 12 months following successful treatment, and investigates the influence of socio-economic, geographical and environmental factors. A longitudinal study of 642 individuals aged over 5 years was conducted in Minas Gerais State, Brazil from June 2004 to March 2006. Risk factors were assessed using interval censored regression for the rate and negative binomial regression for intensity. The crude rate and intensity of hookworm re-infection was 0·21 per year (95% confidence interval (CI) 0·15-0·29) and 70·9 epg (95% CI 47·2-106·6). For S. mansoni the rate was 0·06 per year (95% CI 0·03-0·10) and intensity 6·51 epg (95% CI 3·82-11·11). Rate and intensity of re-infection with hookworm were highest among males and positively associated with previous infection status, absence of a toilet and house structure. Rate and intensity of S. mansoni re-infection were associated with previous infection status as well as geographical, environmental and socio-economic factors. The implications of findings for the design of anti-helminth vaccine trials are discussed.
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Affiliation(s)
- Bonnie Cundill
- London School of Hygiene and Tropical Medicine, London, UK.
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