EXPERIMENTAL TRANSMISSION OF INFLUENZA VIRUS INFECTION IN MICE : III. DIFFERING EFFECTS OF IMMUNITY INDUCED BY INFECTION AND BY INACTIVATED INFLUENZA VIRUS VACCINE ON TRANSMISSION ON INFECTION

Immunization of mice by infection or intraperitoneal injection with homotypic A₂, heterotypic A₀, or recombinant A₀A₂ virus have differing effects on transmission of influenza A₂ virus infection. Immunization by infection with A₂ virus resulted in refractoriness to reinfection either by artificial aerosols or by exposure to infected cage-mates. Immunization by inoculation with inactivated A₂ virus vaccine resulted in a decreased susceptibility to transmitted infection in immunized contacts, but following A₂ virus challenge, transmission of infection by immunized infectors was not altered. Immunization by infection with influenza A₀ virus or recombinant A₀A₂ virus resulted in a decreased susceptibility to transmitted A₂ virus infection in immunized contacts, and to decreased transmission after A₂ virus infection in immunized infector mice. These differing effects on transmission of infection are attributed to differences in specific local immunologic responses following the various immunization procedures.