Each year, approximately 2 million children worldwide die from diarrhea, one fourth of these are caused by rotavirus infections. Indian scientists have developed a live, oral Rotavirus Vaccine (HRV 116E) which is being evaluated in a phase III trial partl y funded by the Research council of Norway (RCN). Live, oral vaccines often induce lower responses in children of low-income countries. It has been suggested that this could be caused by several factors such as interference with maternal antibodies in bre ast milk or with other intestinal infections. In a randomized controlled trial we will therefore assess whether or not breast milk given with the vaccine reduces it's immune response. We will also collect stool samples from all enrolled children and test these samples for other enteric viruses. Anti rotavirus antibodies will be measured in maternal and child serum, saliva from the child and in breast milk. The proportion who seroconvert defined by a four fold increase in serum anti VP-6 antibodies from ba seline to one month after the third vaccine dose will be compared between children where breast milk is withheld and those who are encouraged to give breast milk and between those with and without other enteric virus infections at enrolment. This project will be carried out in collaboration with the partners of the phase III project and we will use the Indian HRV 116E vaccine strain. The collaborative activities will further include a course in vaccinology to be held in India as well as joint supervision of postgraduate students from Norway and India. Partners in this project are the Christian Medical College in Vellore, India, the Society for Applied Studies in New Delhi, India and the University of Bergen, Norway.