CSL Ltd of Australia reported that it has produced the smallest vaccine does that can protect humans against the bird flu virus. However, it admitted that it does not know how this vaccine will work if the virus mutates further. Experts say that it will take months before they can start working on a mutated strain. The H5N1 strain has killed 91 people in East Asia and Middle East and there are a total of 169 confirmed human cases. Cases have been reported in Nigeria and Europe recently.