Availability of new H5N1 prototype strain for influenza pandemic vaccine development

May 2006

Since October 2005, it has been observed that H5 HA genes of the majority of virus isolates from animals and humans received by the WHO H5 Reference Laboratory Network are genetically distinguishable from the earlier virus isolates from South- East Asia, which were represented by the 2 H5N1 prototype vaccine strains, A/Vietnam/1203/2004 and A/Vietnam/1194/2004, developed by WHO in 2004-2005.

At the same time, along with the genetic differences, antigenic variation has also been observed. The 3rd H5N1 prototype vaccine strain, which is the 1st from the new genetic group, was developed from A/Indonesia/5/2005 and made available to the companies/institutions in March 2006 from the WHO Collaborating Centre for Reference and Research on Influenza in CDC Atlanta.

Now, two new H5N1 recombinant vaccine strains developed from A/Bar headed goose/Qinghai/1A/2005 and A/Whooping swan/Mongolia/244/2005 selected from the new genetic group, by the WHO Collaborating Centre at the St. Jude Children's Research Hospital, Memphis USA, are available for distribution, under a Material Transfer Agreement (MTA). As is the case for all other WHO selected and developed influenza prototype vaccine strains, including seasonal and A(H5N1) influenza vaccines, the sequences of haemagglutinin (HA) and neuraminidase (NA) of these new H5N1 recombinant stains can be found on the public web site of Los Alamos National Laboratory database.

Institutions, companies and others interested in pandemic vaccine development who wish to receive these two prototype strains should contact either the WHO Global Influenza Programme at or WHO Collaborating Centre St Jude Hospital at the address below:

WHO Collaborating Centre for Studies on the Ecology of Influenza in Animals, Department of Virology & Molecular Biology, St. Jude Children's Research Hospital, University of Tennessee, 332 North Lauderdale, P.O. Box 318, Memphis, TN 38105, USA (Fax: +1 901 523 2622; email:

Another new H5N1 recombinant vaccine strain developed from A/Turkey/Turkey/1/2005 is in the final stage of safety testing in the National Institute for Biological Standards and Control, United Kingdom.

Studies on antigenic properties of these vaccine reference strains and their relations with the emerging H5N1 viruses are ongoing in the WHO H5 Reference Laboratory Network.

The Global Influenza Programme has been closely monitoring the antigenic and genetic evolution of the circulating viruses, especially human isolates. Countries are encouraged to share with WHO their specimens/isolates, both from humans and animals, in order to be included in WHO's H5N1 vaccine selection/development and other activities of public health significance.