Safety and Immunogenicity Study of a Booster Vaccination With a Non-Adjuvanted H5N1 Influenza Vaccine (Follow Up to Study 810501)

The purpose of this Phase II follow-up study (to study 810501) is to assess the immunogenicity and safety of a booster vaccination with a non-adjuvanted H5N1 influenza vaccine administered 12 to 17 months after a two-dose regimen of different doses of an adjuvanted or non-adjuvanted H5N1 influenza vaccine in a healthy young adult population. A data safety monitoring board will review the safety data after the booster vaccination. The H5N1 influenza antibody persistence 180 days after the booster vaccination will also be assessed.