Oral immunization against influenza virus

Summary

Mice and ferrets were immunized by oral, intranasal or intraperitoneal route with attenuated or inactivated influenza A₂/Aichi/68. Production of antibodies in groups immunized orally was lower than in groups immunized intranasally or intraperitoneally when attenuated virus was administered. When inactivated virus was inoculated the serum antibody response was high following intraperitoneal injection, low following intranasal injection and nil following oral administration.

Deaths occurred between the 3rd and the 11th day after intranasal immunization with partially attenuated virus, showing that immunization by the intranasal route necessitates more attenuated strains than by oral or by intraperitoneal routes. Higher doses of vaccine were required by oral than intranasal or intraperitoneal route to confer an equivalent degree of protection.