An evaluation of influenza immunization: influence of route of administration and vaccine strain.

A field study was undertaken in Tampa, Fla., to assess the efficacy of subcutaneous and aerosol methods of administering vaccine, and to compare the protection afforded by bivalent (A2 and B) influenza virus vaccine and by A2/Hong Kong/68 virus vaccine. Further objectives of the study included a comparison of the effectiveness of single-dose and 2-dose immunization. Approximately 2100 volunteers received, in a double-blind manner, both an injection and an aerosol administration on 2 occasions 3 weeks apart. The results showed that aerosol administration gave a lower over-all protection rate, although the booster dose seemed to have a marked effect. The protection afforded by A2/Hong Kong/68 virus vaccine was considerably greater than that afforded by the bivalent vaccine, particularly when administration was subcutaneous. Results are also given on the occurrence of side-effects and on the correlation between cigarette smoking and the occurrence of influenza-like illness.