Geographical Analysis in Vaccine Trials
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Project Summary
This project develops and tests spatial analytical methods for vaccine trials because existing methods limit the extrapolation of results and are sometimes of questionable validity. It uses these spatial methods to control for heterogeneous disease exposures (spatial effect modifiers) and spatial bias in disease outcomes (spatial confounders). In 1985, a community-based, individually randomized oral cholera vaccine trial was conducted in Matlab, Bangladesh. This study uses a geographic information system (GIS) to determine: (1) How cholera vaccine efficacy varies spatially in the study area; (2) What ecological socio-environmental variables are related to cholera vaccine efficacy (i.e., which variables are effect modifiers); (3) How protective efficacy varies with access to treatment facilities (i.e., whether access is a spatial confounder; and (4) Whether cholera incidence in the placebo group is related to vaccine coverage rates (i.e., is herd immunity important).
The project is presently being extended to include not only spatial analytical methods but also social network analysis methods for vaccine trial evaluation. The extended study uses social network analysis, a GIS, and remote sensing technologies to determine: (1) How cholera vaccine efficacy varies spatially within different spatial and environment contexts; (2) How protective efficacy varies within social networks; and (3) How spatial and social network information can jointly be used to assess the effectiveness of vaccines.
Project Team Members
Michael Emch
Elisabeth Root
Sophia Giebultowicz
Publications
Emch, M., M. Ali, E.D. Root and M. Yunus. 2009. Spatial and Environmental Connectivity Analysis in a Cholera Vaccine Trial. Social Science and Medicine, 68(4): 631-637. link to article
Ali, M.; Emch, M.; von Seidlein, L.; Yunus, M.; Sack, D.A.; Holmgren, J.; Rao, M.; and Clemens, J.D. (2005) Herd immunity conferred by killed oral cholera vaccines in Bangladesh: a reanalysis. Lancet. Jul 2-8;366(9479):44-9. link to article
Emch, M; Ali, M.; Park, J.K.; Yunus, M.; Sack, D.; and Clemens, J.D. (2006) Relationship between neighbourhood-level killed oral cholera vaccine coverage and protective efficacy: evidence for herd immunity. International Journal of Epidemiology. 35: 1044-1050. link to article
Ali, M.; Goovaerts, P.; Nazia, N.; Haq, MZ; Yunus, M.; Emch, M. (2006) Application of Poisson kriging to the mapping of cholera and dysentery incidence in an endemic area of Bangladesh. International Journal of Health Geographics. 5(45):1-11. link to article
Emch, M.; Ali, M.; Acosta, C.; Yunus, M.; Sack, D.; and Clemens, J.D. (2006) Efficacy calculation in randomized trials: Global or local measures? Health & Place. 13: 238-248. link to article
Ali, M.; Emch, M.; Yunus, M.; Sack, D.; Lopez, AL, Holmgren, J.; Clemens, J. (2008) Vaccine protection of Bangladeshi infants and young children against cholera: Implications for vaccine deployment and person-to-person transmission. The Pediatric Infectious Disease Journal. 27(1): 33-37. link to article
Emch, M.; Ali, M.; Root, E.D.; Yunus, M. (2009, in press) Spatial and environmental connectivity analysis in a cholera vaccine trial. Social Science & Medicine.
Presentations
Giebultowicz, S.; Root, E. and Emch, M. “Examining the Role of Social Networks and Herd Immunity in a Cholera Vaccine Trial in Bangladesh” Paper presented at Population Association of America Annual Meeting, Detroit, MI, 05/02/09.
Giebultowicz, S.; Root, E. and Emch, M. "Indirect Protection due to Social Networks and Space in a Cholera Vaccine Trial" SouthEastern Division of the Association of American Geographers Annual Conference, Greensboro, NC. Poster presented on 10/24/08.
Funding
National Science Foundation, BCS Program, “Geographical Analysis in Vaccine Efficacy Trials: Spatial Confounders, Effect Modifiers, and Herd Immunity Measurement.” 2003-06.
National Institute of Allergies and Infectious Disease, NIH, “Geographical Analysis in Vaccine Efficacy Trials.” 2003-05.
National Institute of Allergies and Infectious Disease, National Institutes of Health, “Integration of Spatial and Social Network Analysis in Vaccine Trials.” RO3, Emch, M.E. (PI); Bearman, P.; Ali, M.; Clemens, J. 2009-11 (in review).
Collaborating Institutions
International Centre for Diarrhoeal Disease Research, Bangladesh
