Since the discovery of rotavirus in 1973, vaccine technology has moved from the use of monovalent attenuated animal rotavirus strains to the development of multivalent human-animal reassortment vaccines. The first licensed vaccine, a rhesus-human tetravalent vaccine, was licensed in 1998. This vaccine was withdrawn from the market a year later when it was noted that administration of vaccine was associated with an increased risk of intussusception. The future of rotavirus vaccine is dependent on the reasons for this association that have yet to be discovered.