21 December 2006

The WHO Global Influenza Programme is continuing to monitor the antigenic and genetic evolution of circulating H5N1 viruses and their human isolates. In August 2006, WHO reported¹ that analysis of newly isolated viruses collected from both animals and humans indicated that the H5 haemagglutinin (HA) genes had become genetically distinguishable from the H5N1 viruses that had previously been selected for vaccine development. Furthermore, there was also evidence of antigenic variation among the recent viruses. Since then, WHO Collaborating Centres (WHO CCs) and H5 Reference Laboratories have been developing several new recombinant H5N1 vaccine viruses that are representative of this newly discovered genetic sub-group of clade 2 viruses.

The WHO CC in the Centers for Disease Control and Prevention (CDC), Atlanta USA and the China Centers for Disease Control, Beijing China have together developed a new recombinant H5N1 virus from A/Anhui/1/2005 selected from clade 2, sub-clade 3. The recombinant vaccine virus is available for distribution, under a Material Transfer Agreement (MTA). The sequences of haemagglutinin (HA) and neuraminidase (NA) of the new H5N1 recombinant vaccine virus can be found on the public web site of Los Alamos National Laboratory database together with all other WHO selected and developed influenza vaccine viruses for both seasonal and H5N1 influenza.

Institutions, companies and others interested in pandemic vaccine development, who wish to receive this recombinant vaccine virus should contact either the WHO Global Influenza Programme at whoinfluenza@who.int or WHO CC CDC at the address below:

WHO Collaborating Center for Surveillance, Epidemiology and Control of Influenza, Centers for Disease Control and Prevention, 1600 Clifton Road, Mail stop G16, Atlanta, GA 30333, USA (fax: +1 404 639 23 34; e-mail: rdonis@cdc.gov).

Review of the needs and the actual development of H5N1 vaccine viruses representative of circulating strains in the world are ongoing in WHO CCs and H5 Reference Laboratories. The WHO Global Influenza Programme will continue to select, verify and develop new H5N1 candidate vaccine viruses from genetically and/or antigenically different groups of circulating viruses for the purposes of vaccine research and development.