Immune responses in serum and respiratory secretions following vaccination with a live cold-recombinant (CR35) and inactivated A/USSR/77 (H1N1) influenza virus vaccine.

One hundred adult volunteers were administered inactivated vaccine (20 micrograms/0.5 cc) intramuscularly (IM) or intranasally (IN), or 10(4.7) TCID50 of a live cold-adapted vaccine (CR35) IN. Microneutralization (Nt) and radioimmunoprecipitation methods were employed to measure hemagglutinin antibody responses in sera, nasal washes, and in bronchopulmonary lavage fluids. In unprimed recipients, the relative frequency of serum antibody response and magnitude of rise was highest following the IM-inactivated vaccine (100%) and lowest after IN-live vaccine (29%). However, in individuals with pre-existing antibody, the three vaccines given were comparably immunogenic. Occurrences of secretory IgA hemagglutinin antibody in nasal washings were more frequently associated with topical administration of live or inactivated vaccine, whereas, IgG hemagglutinin antibody responses occurred with equal frequency in nasal washings in all three vaccine groups. Analysis of the hemagglutinin antibody responses in the lower respiratory tract showed that the IN-live vaccine favored the induction of secretory IgA hemagglutinin antibody and the IM-inactivated vaccine stimulated a more frequent IgG hemagglutinin antibody response.