[Effectiveness of live influenza vaccines obtained by strain recombination and passages].

A comparative study of the immunizing activity of strain variants derived from one epidemic influenza virus A/USSR/77 (H1N1) by using different attenuation methods was carried out. Serial passages in chick embryos preserved the biological activity of the virus better than genetic recombination which was manifested by a significant superiority of the passaged virus over the reassortant in the capacity of replicating in the upper respiratory tracts of the vaccinees, of inducing immune responses and creating the protection of the portals of entry of infection. The problem of optimal preservation of biological potentials of influenza virus in the process of attenuation is discussed.