[Comparison between killed subunit influenza vaccines and whole virion preparations: study of reactions and protective efficacy in children and adults].

Three hundred eight subjects (of whom 103 children aged 6-12 years) were vaccinated with trivalent--A/USSR/90/77 (H1N1), A/Texas/1/77 (H3N2), B/Hong Kong/8/73 strains--influenza virus vaccines, two of them sub-unit and the third whole-virus preparation. Children and adolescent received two doses with an interval of 4 weeks, adults one dose only. The results of the determination by single radial diffusion test of the hemagglutinin amount for each of the three vaccinal strains and the data of the mouse immunogenicity test show that the antigenic content of A/USSR/90/77 strain in the sub-unit preparations was lower than expected from the concentration in I.U. reported by the vaccine manufacturers. Therefore it is pointed out the necessity to control the antigenic content of inactivated influenza virus vaccines with methods more adequate than those currently adopted. Sub-unit vaccines were much less reactogenic than the whole-virus preparation particularly in the youngest group of vaccinees. The immunogenicity (assessed by serum h.i.a. titers) of sub-unit vaccines, even after a single dose, turned out to be good and equal to that of the whole-virus preparation in primed subjects. In unprimed individuals, as it is shown by the data relative to the A/USSR/90/77 strain in sero-negative children, a two dose regimen is required. In these vaccines the whole-virus vaccine was more immunogenic than the sub-unit preparations, probably because of the lower content in the H1N1 strain of the latter. The increase from 1 ml (1 dose) to 1.6 ml the amount of vaccine, as experimented in adults with one sub-unit preparation, was not followed by an increase in reactogenicity. The larger dose did not influence the antibody response of primed subjects. On the contrary in unprimed vaccinees, as the youngest under 24 years without preexisting antibodies to the H1N1 strain in the present trial, the higher antigenic content produced a marked positive effect.