Secretory immune response after nasal vaccination with live attenuated influenza viruses

Immunoglobulins and virus-specific antibody in nasal secretions were measured in 18 volunteers before and after intra-nasal vaccination with two live-attenuated type A influenza virus strains. Specific serum antibody rises occurred in 14 out of 18 vaccinees; of those, 11 and 10, respectively, showed significant increase of IgA concentration and of virus-specific antibody in nasal secretions collected 2-4 weeks after vaccination. In one case, a volunteer showed appreciable increase of virus neutralizing antibody in nasal secretions without increase of local IgA concentration and of serum HI antibody. This data indicate that administration of live virus vaccines by upper respiratory route confers effective immunity associated with local antibody synthesis.