Early phase II trial of human rotavirus vaccine candidate RV3.

A naturally attenuated, human neonatal strain, rotavirus vaccine candidate RV3, was tested in a limited phase II randomized double-blind controlled trial. Doses of 1 ml, containing placebo or 6.5 x 10(5) fluorescent cell forming units (fcfu) of virus in AGMK cells, were given at 3, 5 and 7 months of age. Limited replication in the small intestine is implied by the lack of virus excretion, and by the occurrence of an immune response in only 46% of the infants. However, those who developed an immune response were partially protected against rotavirus disease during the subsequent winter epidemic (protective efficacy 54%), supporting observations of protection induced by natural infection by this strain. Protection appeared to be heterotypic. Further trials are warranted, employing strategies to increase immunogenicity of this human rotavirus candidate vaccine.