The United Nations health agency has reported "encouraging progress" in producing vaccine against human bird flu which, in worst case scenario, could mutate to cause pandemic with the potential of killing millions.
But the World Health Organization (WHO) said the bad news is that the world does not have the capacity to meet potential global demand even as some independent experts said that the efficacy of the vaccine in humans is yet to be fully demonstrated.
The agency is negotiating with 16 manufacturers in ten country developing prototype of the vaccine against H5N1 virus, five of whom are developing focusing on other strains including H9N2, H5N2 and H5N3.
The results presented at just concluded experts meeting, WHO said, have "convincingly demonstrated" that vaccines can bring about a potentially protective immune response against strains of H5N1 virus found in a variety of geographical locations, WHO said.
Some of the vaccines, it said, work with low doses of antigen, which means that significantly more vaccine doses can be available in case of a pandemic.
But it warned that in spite of the encouraging progress, the world still lacks the manufacturing capacity to meet potential global pandemic influenza vaccine demand as current capacity is estimated at less than 400 million doses per year of trivalent seasonal influenza vaccine.