Technically, the high mutation rate should not be problematic provided the vaccine is produced fast enough (and six weeks is very fast for a flu vaccine). However, conventional methods are slow and rely on the annual prediction of the emerging strains. So far attempts to produce an H5-vaccine have failed because the H5 protein is not very immunogenic. That is: it does not elict a strong immune response so it does not confer strong protection.

All this indicates that they use a new way to produce a flu vaccine. Which is good, because with conventional methods the production capacity of all flu vaccine-producers put together will not be sufficient to provide the West (let alone the world) with vaccines in a timely manner when the pandemic breaks out.

Still, it may be a good idea to hoard some anti-flu drugs.