Immunogenicity of Two Dosages of Inactivated, Split-Virion Influenza Vaccine Given by an Alternate Route in the Elderly

All marketed influenza vaccines are injected by the intramuscular route. This study will test whether an influenza vaccine is effective when injected by other route than into the muscle. In order to prove this, the amount of antibodies in the blood will be measured before and after vaccination. In addition, the safety of both influenza vaccines will be tested by evaluating all serious reactions occurring after vaccination. The vaccine injected in this study is similar to the sponsor's marketed intramuscular influenza vaccine (Vaxigrip).

Primary Objective:

To demonstrate and compare the immune response of two dosages of influenza vaccine administered by an alternate route to the intramuscular administration of the vaccine.

Secondary Objectives:

• To compare the immune response 21 days after vaccination between each investigational group versus intramuscular group for each influenza strain.
• To describe the safety profile after the vaccination in each study group
• To describe the compliance of the two dosages of the vaccine administered by the alternate route with the European Medicine Agency.

Observational Objectives:

• To describe the safety profile during the 21-day period following an intramuscular revaccination in each group and the possibility of any reaction at the first injection site.
• To describe the pain at the injection site with a Visual Analog Scale and the acceptability of the injection using a questionnaire in each group.
• To describe the leakage appearing at the injection site immediately after the alternate route injection and to explore the relationship with immunogenicity.
• To evaluate the cellular mediated immune response in a subset of subjects.