Rotaviruses are a major cause of gastroenteritis in infants and children. In the US, Australia and Japan, 34 to 63% of hospitalisations of children for acute diarrhoeal diseases are associated with rotavirus infection. An effective vaccine would therefore have a major impact. Live attenuated bovine rotavirus vaccines have had variable protective efficacy in clinical trials. A reassortant human bovine vaccine containing the bovine rotavirus WC3 and the human serotype G1 rotavirus W179 (W179-9) is under phase III development with Merck & Co and the National Institutes of Health in the US. The vaccine appears to be highly effective in the prevention of clinically significant serotype G1 human rotavirus infection.