Mohammad Ali, PhD, is a senior scientist in the Department of International Health at Johns Hopkins Bloomberg School of Public Health. He introduced geographic information systems in vaccine evaluation studies, and his newest spatial epidemiology studies investigate the herd effect as well as the effectiveness of cholera vaccines. Dr. Ali is the author or co-author of nearly 125 publications, a reviewer of several peer-reviewed journals, an adjunct professor at Seoul National University, and a research consultant at the University of North Carolina at Chapel Hill.