offit worked for 25 years on the development of a safe and effective vaccine against rotavirus, which is a cause of diarrhea, and which kills almost 600,000 children a year worldwide, about half as many as malaria kills; most deaths are outside the west. his interest in the disease stemmed from the death of a 9-month-old infant from rotavirus-caused dehydration while under his care as a pediatric resident in 1979.