The United States government hopes to obtain enough vaccine in 2006 to treat 4 million people. However, it is unclear whether this vaccine would be effective against a hypothetical mutated strain that would be easily transmitted through human populations, and the shelf life of stockpiled doses has yet to be determined.The New England Journal of Medicine reported on March 30, 2006, on one of dozens of vaccine studies being conducted. The Treanor et al. study was on vaccine produced from the human isolate (A/Vietnam/1203/2004 H5N1) of a virulent clade 1 influenza A (H5N1) virus with the use of a plasmid rescue system, with only the hemagglutinin and neuraminidase genes expressed and administered without adjuvant. "The rest of the genes were derived from an avirulent egg-adapted influenza A/PR/8/34 strain. The hemagglutinin gene was further modified to replace six basic amino acids associated with high pathogenicity in birds at the cleavage site between hemagglutinin 1 and hemagglutinin 2. Immunogenicity was assessed by microneutralization and hemagglutination-inhibition assays with the use of the vaccine virus, although a subgroup of samples were tested with the use of the wild-type influenza A/Vietnam/1203/2004 (H5N1) virus." The results of this study combined with others scheduled to be completed by spring 2007 is hoped will provide a highly immunogenic vaccine that is cross-protective against heterologous influenza strains.On August 18, 2006. the World Health Organization (WHO) changed the H5N1 strains recommended for candidate vaccines for the first time since 2004. "The WHOs new prototype strains, prepared by reverse genetics, include three new H5N1 subclades.
Aflunov, approved for medical use in the European Union in November 2010. Aflunov contains the flu strain A/turkey/Turkey/1/2005 (H5N1)-like strain (NIBRG-23) (clade 2.2.1). Pumarix, approved for medical use in the European Union in March 2011.In November 2013, the U.S. Food and Drug Administration (FDA) approved an experimental H5N1 bird flu vaccine to be held in stockpiles. In a clinical trial including 3,400 adults, 91% of people age 18-64 and 74% of people age 65 or older formed an immune response sufficient to provide protection. Reported adverse effects were generally mild, with pain at the injection site being the most common adverse effect.H5N1 continually mutates, meaning vaccines based on current samples of avian H5N1 cannot be depended upon to work in the case of a future pandemic of H5N1. While there can be some cross-protection against related flu strains, the best protection would be from a vaccine specifically produced for any future pandemic flu virus strain. Daniel R. Lucey, co-director of the Biohazardous Threats and Emerging Diseases graduate program at Georgetown University, has made this point, "There is no H5N1 pandemic so there can be no pandemic vaccine." However, "pre-pandemic vaccines" have been created; are being refined and tested; and do have some promise both in furthering research and preparedness for the next pandemic.