Studies with a live influenza A vaccine in army personnel

A live attenuated influenza A vaccine, produced from an inhibitor-resistant recombinant strain, was administered intranasally to 46 volunteers from the Army during the southern winter of 1973. To compare the acceptibility, immunogenicity and efficacy of this vaccine, a killed subunit vaccine was administered to 20 volunteers, and an intranasal placebo to 45 others. Results indicate that the live intranasal vaccine was as well tolerated as the killed vaccine and that there was no evidence of shedding of virus from the nose in the 14 days following vaccination. Both the killed and the live vaccines stimulated the production of circulating haemagglutination-inhibition antibody, but antibody to neuraminidase was induced only by the live vaccine. No conclusions could be drawn about the efficacy of the two vaccines in producing local antibodies because these were largely undetectable by the methods used. Volunteers were followed for a 12-month period, which included the 1973 and 1974 influenza seasons, and an attempt was made to determine the virological aetiology of all their respiratory infections during this period. Epidemic influenza did not occur in thepopulation group from which these volunteers were drawn, so the comparative protection rates of the two vaccines could not be assessed.