Virulence of temperature-sensitive mutants of influenza virus.

The acquisition of temperature-mutant (ts) defects in a strain of influenza virus has been shown in mice to be associated with diminished virulence, though the antibody-producing stimulus remained. It is suggested that three advantages may make ts strains potential sources of attenuated live influenza vaccine-the ease of obtaining the strains, the ease of testing the vaccine strain, and the high yield of vaccine doses from a single egg.