Study to Evaluate Safety and Immunogenicity of Different Priming and Booster Regimens With Adjuvanted H5N8 and/or H5N6 Influenza Vaccine in Adults

MF59-adjuvanted cell-culture derived subunit inactivated monovalent A/H5N8 vaccine (aH5N8c) for intramuscular administration, containing intermediate dose H5N8 hemagglutinin + standard dose MF59 (approximately 0.5 mL total volume)

MF59-adjuvanted cell-culture derived subunit inactivated monovalent A/H5N6 vaccine (aH5N6c) for intramuscular administration, containing intermediate dose H5N6 hemagglutinin + standard dose MF59 (approximately 0.5 mL total volume)

MF59-adjuvanted cell-culture derived subunit inactivated monovalent A/H5N8 vaccine (aH5N8c) for intramuscular administration, containing intermediate dose H5N8 hemagglutinin + standard dose MF59 (approximately 0.5 mL total volume)

MF59-adjuvanted cell-culture derived subunit inactivated monovalent A/H5N6 vaccine (aH5N6c) for intramuscular administration, containing intermediate dose H5N6 hemagglutinin + standard dose MF59 (approximately 0.5 mL total volume)

MF59-adjuvanted cell-culture derived subunit inactivated monovalent A/H5N8 vaccine (aH5N8c) for intramuscular administration, containing intermediate dose H5N8 hemagglutinin + standard dose MF59 (approximately 0.5 mL total volume)