Further researches on live influenza virus vaccines.

A/Port Chalmers 1/73 and A/Victoria 3/75 live vaccines were well tolerated after oral administration and showed good immunogenic properties in subjects devoid of immune-defence or having low antibody titer. A/Victoria 3/75 vaccine was prepared before the epidemiological appearance of the corresponding virus which demonstrates that the preparation of a vaccine with new strains can be made in a comparatively short time. Our experiments and controls allow us to establish that the oral administration of influenza virus, grown on chicken kidney embryo, elicits the appearance of HI antibodies in a high number of susceptible subjects. A 60% seroconversion rate obtained after administration of two doses represents a favourable result, the more so as the vaccine can be considered absolutely safe in very young subjects.