MANILA, Jan. 27 (Xinhuanet) -- Scientists need at least six monthsto formulate a vaccine against the bird flu virus, a World Health Organization (WHO) official said Tuesday.

    "It's mutated. We have to start from the drawing board and create a prototype vaccine for this virus," the Philippine Daily Inquirer on-line news quoted Peter Cordingley, spokesman of the Manila-based WHO Western Pacific Region Office, as saying.

    The bird flu disease has killed at least six people in Asia andresulted in a temporary ban on the importation of chickens from affected countries.

    The Philippine Department of Health had said humans could only contract bird flu from contaminated fowl but doctors feared the virus could mutate to allow its transmission from an infected human to a healthy one.

    Poultry farms in Asian countries like Japan, China, Vietnam, South Korea and Thailand have been affected by the bird Flu.

    President Gloria Macapagal-Arroyo has ordered a ban on all poultry imports from Asian neighbors to prevent the virus from entering the country.

    Meanwhile, the WHO also warned people carrying out poultry culls to don protective equipment or risk contracting the deadly virus in view of the bird flu epidemic in Asia, adding that exposure to infected poultry and their feces, or dust or soil contaminated with feces, could result in human infection.

    Likewise, it said environmental clean-up should be carried out in areas of culling, using the same protective measures. Enditem