Rotavirus is the most common cause of severe diarrhea worldwide. In developing countries, rotavirus may cause 600,000 to 870,000 deaths each year, accounting for an estimated 20 to 25% of all deaths due to diarrhea and 6% of all deaths among children< 5 years of age [1, 2]. Because of the magnitude of disease associated with rotavirus infections and because public health interventions to provide clean water and improved sanitation are unlikely to decrease the incidence of disease, vaccines are being developed as the first strategy for prevention. Several live, oral rotavirus vaccines have been tested in field trials and have demonstrated an efficacy of 80% or more against severe rotavirus infections with minimal adverse side effects. The first rotavirus vaccine, tetravalent rhesus rotavirus vaccine (RRV-TV), was licensed for use in the United States in 1998. In the past, rotavirus vaccines that demonstrated high efficacy in developed countries appeared to have lower efficacy in developing countries. This highlights the need for further evaluation of rotavirus vaccines in developing countries, where they would have the greatest impact in preventing childhood mortality. The successful development of rotavirus vaccines and their public health application could bring together two global agendas for child survival in developing countries promoted by the World Health

Organization (WHO), the control of both diarrheal diseases and vaccine-preventable diseases. Immunization is recognized to be the most cost-effective public health program in developing countries. Between 1980 and 1990, vaccine coverage by the Expanded Program of Immunization (EPI) increased from less than 20% to nearly 80%, making immunizations accessible to most of the world's children. Furthermore, diarrheal diseases are recognized to be a major cause of childhood mortality, responsible for 20ą25% of deaths among children< 5 years, but efforts to prevent this mortality by programs of oral rehydration therapy, breast-feeding or improving sanitary and water infrastructures, have failed to achieve the anticipated gains. The inclusion into EPI of rotavirus vaccines that potentially could prevent the most common cause of severe diarrhea in children could reinforce efforts to sustain high levels and timeliness of immunization coverage. In January 1997 and in July 1998, WHO's Global Programme on Vaccines, the Children's Vaccine Initiative and the Centers for Disease Control and Prevention (CDC) convened meetings to assess the status of rotavirus vaccine for use in developing countries and to outline plans to speed the availability and introduction of rotavirus vaccines. This paper served as the background document for the meeting in 1997 to (1) review the epidemiology and burden of disease associated with rotaviruses in developing countries;(2) reexamine the status of rotavirus vaccine development and the experience with these vaccines in developing countries;(3) discuss factors that will affect the introduction of rotavirus vaccines and their use by EPI; and (4) identify areas in which further research will be necessary to expedite introduction of a rotavirus vaccine in developing countries.