This piece from Reuters shows something unexpected: according to the US Centers for Disease Control, rotavirus vaccines do not simply prevent diarrhoea in young children (they seem to prevent about 80 percent of cases); they stop illness in the adults and older children who live around infected children (about half of adult cases were prevented although hardly any adults were immunised). These findings are about the US where the major concern is reducing hospital stays; rotavirus disease kills millions of babies in the developing world.