It was found that neonatal avirulent strains 116E and I321 induce protective immunity and offer clinical protection for at least one year. Both these strains are well characterized and the safety studies have been done in animal models. These candidate vaccine strains have been evaluated for safety and immunogenicity in adults and children (2 to 12 years of age) by a randomized double blind placebo controlled trial in Cincinnati, USA. In India, the diversity of rotavirus strains is greater and there is greater prevalence of malnutrition and co-infection with other enteric pathogens. These vaccines have therefore, also been tested in India.