Vepacel (R) is a prepandemic influenza vaccine (whole virion, Vero cell-derived, inactivated) containing antigen of H5N1 strain A/Vietnam/1203/2004 and is approved for use in the EU. Clinical immunogenicity studies with the vaccine have demonstrated good functional neutralizing antibody responses against the vaccine strain (A/Vietnam/1203/2004), and cross-reactivity against H5N1 strains from other clades. In general, adverse events observed in clinical immunogenicity studies with a whole virions H5N1 vaccine (A/Vietnam/1203/2004) were similar to those reported with non-adjuvanted, inactivated, split virion seasonal influenza vaccines.