The present status of rotavirus vaccine development.

Rotavirus infection is one of the most important causes of morbidity in young children throughout the world. The high associated mortality in Southeast Asia (and elsewhere) warrants the development of a vaccine. It is probable that most of the life-threatening watery diarrhoea due to rotavirus infection occurs as a result of primary infection in children aged 6-18 months after protection due to maternal antibody has diminished. Thus rotavirus vaccines are targeted at young infants from birth to 3 months of age. At present three candidate rotavirus vaccines (RIT-4237, MMU-18007, WC3) have undergone trials in young children. A bovine rotavirus strain (RIT-4237), was shown to be safe, immunogenic and efficacious in prevention of severe rotavirus diarrhoea in young children in Finland. However it was found to be weakly immunogenic in infants in developing countries, and to have only low efficacy in prevention of disease. A simian rotavirus strain (RRV, MMU-18006) has proved to be highly immunogenic and its reactinogenicity to be diminished by pre-existing maternal antibody (in infants aged 1-4 months). It has high efficacy against clinically severe rotavirus infection. However protection is homotypic against human serotype 3 only so that eventually a multivalent vaccine incorporating reassortant rotavirus strains that protect against human serotypes 1, 2, 4 (and other newer serotypes) may be required. It is hoped that, once safe immunogenic and protective candidate rotavirus vaccines are identified, they can be administered in an acceptable form with no alteration to existing immunization schedules.