Oral influenza vaccination with live attenuated viruses. 1. Acceptability, immunogenicity and transmissibility.

151 subjects were vaccinated by oral route with live attenuated influenza virus vaccine, bivalent A and B, prepared in the U.S.S.R. Each subject received two vaccine doses with a 10-day interval. Vaccination did not bring about any important clinical manifestation and the incidende of the symptoms after vaccination was not significantly different in comparison with what observed in the non vaccinated cohabitants. The vaccine showed good immunizing activity: among the subjects who before vaccination, had a HI antibody titer lower than 1/16, 91% responded for A type, and 70% for B type. Several subjects with starting low antibody titers also responded to vaccination. Among the cohabitants of the vaccinated no influenza virus infections were serologically ascertained, thus showing that no transmission of the virus from the vaccinated to the cohabitants occurred.