PSI Vaccines SIG Webinar: Assessing Population Level Vaccine Effectiveness Under Different Study Designs

Date: Thursday 20th October 2022
Time: 16:00-17:00 BST | 17:00-18:00 CEST | 11:00-12:00 EDT
Location: Online
Speaker: Mohammad Ali

Who is this event intended for? Statisticians working in Vaccines.
What is the benefit of attending? Attendees will have the opportunity to learn about statistical methods.


You can now register for this webinar, which is free of charge for both Members and Non-Members of PSI.
To register, please click here.


The population level effectiveness of a vaccine may arise as the result of direct protection of vaccines and vaccine herd protection, which may protect non-vaccines, vaccines, 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 vaccine in public health program. This presentation provides a brief description of the herd protective effects of the oral cholera vaccines, as an example, that have been evaluated for herd protection in various study settings, leveraging the geographic information system (GIS) tools for analyses. The study designs include individually randomized clinical trials, cluster randomized clinical trials, observational cohort studies, and observational case-control studies. In all 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 use of the GIS tools may effectively assess population level vaccine effectiveness in different study designs.

Speaker details



Mohammed Aliedit
Mohammad Ali

In 1984, I started my research career at the International Center for Diarrheal Disease Research, Bangladesh (ICDDR,B) focusing on data management and statistical analysis of a large clinical trial. Subsequently, I was involved in various studies on population and health at the Center. After completion of my Ph.D. in the field of spatial epidemiology, I joined at the International Vaccine Institute (IVI), Seoul, Korea as the Senior Scientist, and the Head of Biostatistics Unit in early 2001. I introduced Geographic Information System in vaccine evaluation studies for the various research sites of IVI. My spatial epidemiology studies investigated the effectiveness of cholera vaccines, the approach demonstrated that the use of geographic variations in vaccine coverage can help evaluate the indirect protective effects of the vaccine. This method is applicable to trials of a wide range of vaccines before they are introduced into public health practice. In addition, I used GIS, satellite remote sensing, and spatial modeling techniques in research that is grounded in geographic theories of human-environment interaction for generating hypotheses about potential causes of the health problems. I created model for the emergence and fluctuations of cholera by integrating spatial data sets including satellite imagery derived from different sensors, climatic variables, and socio-demographic characteristics (population distribution, and socio-economic status) of the people. In late 2013, I joined at the Johns Hopkins University as a Senior Scientist. At the university, I developed protocols and research studies, published scientific papers, led statistical analysis activities involving multiple institutions, developed data management and statistical analysis plans for the clinical trials, ensured standardization of methods and the quality of the data by assessing and assisting study sites in the design and conduct of the study, mentored MSPH and PhD students, and taught a course on the spatial analysis of health events. Since beginning of 2020, I have working as a Biostatistics lead for pneumococcal franchise at the Pfizer VAC-Medical and involved in scientific data analysis of the various clinical studies around the globe.

I am author or co-author of more than 200 publications and book chapters, reviewer of several peer-reviewed journals, Editor of PLoS ONE, and worked as a Research Consultant in several research institutes.

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