Zambia recently introduced routine infant immunization against rotavirus - the most important cause of severe gastroenteritis and diarrhoea mortality in children. Although vaccines like Rotarix are a cost effective tool against infectious diseases, live oral vaccines can be less immunogenic and efficacious in developing world settings as compared with industrialized countries. Reasons behind this phenomenon are not well understood, but may relate to continued maternal antigen exposure and high level maternal immunity that is passed to the foetus/newborn transplacentally and/or through breast milk.