Model citizen – Authors' reply
Authors: Oliver J Brady, Hannah C Slater, Peter Pemberton-Ross, Edward Wenger, Richard J Maude, Azra C Ghani, Melissa A Penny, Jaline Gerardin, Lisa J White, Nakul Chitnis, Ricardo Aguas, Simon I Hay, David L Smith, Erin M Stuckey, Emelda A Okiro, Thomas A Smith, Lucy C Okell
Journal: The Lancet Global Health (2017)

Tom Peto and colleagues point out, reasonably, that the effect of mass drug administration (MDA) on malaria could be affected substantially by patterns of human movement, and that our Article1Brady OJ Slater HC Pemberton-Ross P et al.Role of mass drug administration in elimination of Plasmodium falciparum malaria: a consensus modelling study.Lancet Glob Health. 2017; 5: e680-e687Summary Full Text Full Text PDF PubMed Scopus (52) Google Scholar does not consider the effects of the specific patterns of movement they observed in Cambodia and west Africa. The purpose of our Article1Brady OJ Slater HC Pemberton-Ross P et al.Role of mass drug administration in elimination of Plasmodium falciparum malaria: a consensus modelling study.Lancet Glob Health. 2017; 5: e680-e687Summary Full Text Full Text PDF PubMed Scopus (52) Google Scholar was to derive general results about the possible effect of MDA and to test how robust these are to the assumptions in different models, so we avoided assumptions about population movement that are specific to any particular place. Migration is among several factors that the different groups in our collaboration have investigated as potential modifiers of the effects of mass treatment in specific situations. For those analyses, we have used field data or realistic assumptions of migration rates.2Crowell V Briet OJ Hardy D et al.Modelling the cost-effectiveness of mass screening and treatment for reducing Plasmodium falciparum malaria burden.Malar J. 2013; 12: 4Crossref PubMed Scopus (25) Google Scholar, 3Gerardin J Bever CA Bridenbecker D et al.Effectiveness of reactive case detection for malaria elimination in three archetypical transmission settings: a modelling study.Malar J. 2017; 16: 248Crossref PubMed Scopus (25) Google Scholar, 4Silal SP Little F Barnes KI White LJ Hitting a moving target: a model for malaria elimination in the presence of population movement.PLoS One. 2015; 10: e0144990Crossref Scopus (24) Google Scholar Human migration is a particularly complicated modifier; the endemicity of malaria in the places from which immigrants or temporary visitors originate could be important, not just the season and extent of migration. A thorough empirical investigation of the implications of different patterns of migration for the effect of MDA would require a prohibitively complex set of field trials. Corresponding in silico analyses, parameterised with local field data, are more feasible but still represent an extensive piece of research in their own right, which is well beyond the scope of our Article.1Brady OJ Slater HC Pemberton-Ross P et al.Role of mass drug administration in elimination of Plasmodium falciparum malaria: a consensus modelling study.Lancet Glob Health. 2017; 5: e680-e687Summary Full Text Full Text PDF PubMed Scopus (52) Google Scholar Some of our research groups use extensive field data collection for this exact purpose.5Marshall JM Toure M Ouedraogo AL et al.Key traveller groups of relevance to spatial malaria transmission: a survey of movement patterns in four sub-Saharan African countries.Malar J. 2016; 15: 200Crossref PubMed Scopus (30) Google Scholar The questions addressed in our Article1Brady OJ Slater HC Pemberton-Ross P et al.Role of mass drug administration in elimination of Plasmodium falciparum malaria: a consensus modelling study.Lancet Glob Health. 2017; 5: e680-e687Summary Full Text Full Text PDF PubMed Scopus (52) Google Scholar were raised by WHO for their Evidence Review Group on mass treatment of malaria, which contains many experts who work directly on MDA interventions. Furthermore, several ongoing modelling exercises are being carried out by the authors of our Article1Brady OJ Slater HC Pemberton-Ross P et al.Role of mass drug administration in elimination of Plasmodium falciparum malaria: a consensus modelling study.Lancet Glob Health. 2017; 5: e680-e687Summary Full Text Full Text PDF PubMed Scopus (52) Google Scholar in collaboration with control programmes to assess the potential effect of MDA in specific settings.6Stuckey EM Miller JM Littrell M Chitnis N Steketee R Operational strategies of anti-malarial drug campaigns for malaria elimination in Zambia's southern province: a simulation study.Malar J. 2016; 15: 148Crossref PubMed Scopus (19) Google Scholar We agree with Peto and colleagues on the importance of modelling groups and field researchers working closely together to better inform models and improve predictions of intervention outcomes. Involvement of modellers in trial design and operational planning for specific interventions allows questions to be framed as accurately as possible for relevant geographies and broader policy recommendations, and we hope that the number of these exercises will increase in the coming years. ACG declares grant funding from the UK Medical Research Council (MRC), Bill & Melinda Gates Foundation, the Wellcome Trust, the Medicines for Malaria Venture, and WHO. She has also received consultancy contracts in the past 3 years from the Medicines for Malaria Venture, Oxford Policy Management, and The Global Fund to Fight AIDS, Tuberculosis and Malaria. EMS and EAO are or have been employed by the Bill & Melinda Gates Foundation. LCO declares grant funding from WHO, the Bill & Melinda Gates Foundation, and Medicines for Malaria Venture, and has received consultancy contracts from Medicines for Malaria Venture and WHO. All other authors declare no competing interests. Role of mass drug administration in elimination of Plasmodium falciparum malaria: a consensus modelling studyMass drug administration has the potential to reduce transmission for a limited time, but is not an effective replacement for existing vector control. Unless elimination is achieved, mass drug administration has to be repeated regularly for sustained effect. Full-Text PDF Open AccessModel citizenOliver Brady and colleagues (May, 2017)1 collaborated with independent modelling groups and reached consensus on a few non-obvious points related to malaria elimination, one of which we find difficult to agree with. Full-Text PDF Open Access