[Development of a rotavirus vaccine. Field trials in Venezuela]

The significance of rotavirus as an agent in acute diarrhea in children is well established, and much effort has been made towards the development of a vaccine for its prevention. In Venezuela, between the years 1985 and 1991, 3 different strategies for a rotavirus vaccine testing in children have been evaluated. The first consisted on the utilization of simian rotavirus (RRV-ser 3). This vaccine was found to be innocuous, immunogenic and induced homotypic protection. However, because there are 4 epidemiologically important virus serotypes, a new strategy was evaluated. This used a reassortant virus that had 10 genes from the simian viral genome and 1 from the human viral genome, that designated the serotype. Three different reassortants with serotypes 1, 2 and 4 were obtained. The studies with these new viruses demonstrated them to be innocuous but, apparently, the immunogenicity was lower when the four serotypes were mixed in a quadrivalent vaccine than when they were applied individually, or in bivalent vaccines. In consequence, a third strategy was tested, using a virus, M37, isolated from a newborn child. This has the advantage with respect to others, that it is from human origin. However the levels of seroresponse to this virus were no very different from those obtained with the quadrivalent vaccine. At the present time, higher concentrations of the quadrivalent vaccine, in 3 doses, are being applied. We hope to develop ta greater response in these children. If this is achieved, we will then evaluate the efficacy of the vaccine to determine the protection against most severe cases of rotavirus diarrhea.