When the H5N1 avian influenza virus re-emerged in Hong Kong in 2003, it triggered a pandemic alert by the World Health Organization (WHO). The newer strains of the virus seem to have a greater pathogenic capacity in animals than did earlier strains. According to WHO, the virus has infected at least 275 people in 10 countries and killed at least 167. While the lethal virus has not yet appeared in the United States, U.S. Health Agencies are rapidly revamping disaster plans to include a coordinated national, state, and local community response to a respiratory pandemic.
One avenue of preparedness lies in the development of a safe and effective vaccine. Recombinant re-assortment technology is being used to prepare vaccines against H5N1 avian influenza strains and clinical trials have been, or are being, conducted at various facilities around the world.
The WHO Global Influenza Programme Network continues to monitor the antigenic and genetic evolution of circulating H5N1 viruses and is working to develop vaccines against these various strains. See www.who.int/csr/disease/avian_influenza/. A pre-pandemic candidate vaccine, (developed by WHO at the Centers for Disease Control and Prevention (CDC) in Atlanta and the China Centers for Disease Control in Beijing), using a new recombinant H5N1 virus from A/Anhui/1/2005 selected from clade 2, sub-clade 3, is available from WHO under a Material Transfer Agreement (MTA).
The March 2006 issue of The New England Journal of Medicine contained a study on a pandemic vaccine by Sanofi-Aventis that showed protective immune response initiation in 45% of healthy people who received the highest dose. A January 2007 meeting of the FDA failed to approve the vaccine. The FDA has approved a "Fast Track" for approval of new vaccines and drugs should the need arise. If approved later, the Sanofi-Aventis vaccine will be the first of its kind on the U.S. market.
However, it remains unclear if these vaccines will be truly effective against the avian influenza organism if it mutates into a strain with more efficient transmissibility from human to human AND maintains its current mortality rate of about 50%.