[Experience in selecting safe heat-sensitive influenza virus A recombinants].

Conditions for genetic recombination and laboratory testing of influenza A virus for rapid production of safe vaccine strains needed in human vaccination were developed. The best donors of attenuation were found to include limitingly attenuated outdated vaccine strains adapted to low temperature and having important differentiating features such as thermosensitivity and reduced optimal temperature of neuraminidase activity. Trials in volunteers of a large collection of recombinants produced by recombination of these donors with various virulent strains circulating in 1972--1976 (A/Victoria/72, A/Port Chalmers/73, and A/Virtoria/75) demonstrated complete safety for man of clones with different combinations of rct/40 and OTNA genetic markers.