Shu Yuelong, senior official with Chinese CDC, said the new vaccine virus was developed by the Chinese CDC and U.S. CDC from the cases of human infections of the deadly virus in southern China.

Researchers found that a newly isolated virus collected from people infected with H5N1 in southern China was distinguishable in terms of antigen from the viruses that had previously been selected for vaccine development, Shu said.

Shu said it was the first time for China to develop a new humanH5N1 vaccine virus, which will be a great contribution to the prevention of the fatal epidemic.

The World Health Organization (WHO) has put the new development on its Web site and said it's available for "institutions, companies and others interested in pandemic vaccine development."

The cases of human infection with bird flu in China numbered 13in 2006, and seven in 2005.

In August 2006, the WHO found that there was antigenic variation among the recent H5N1 viruses. Since then, the WHO Collaborating Centers and H5 Reference Laboratories have been developing several new recombinant H5N1 vaccine viruses