In the coming weeks, at least two vaccine companies are expected to release clinical trial findings that could have an enormous impact on how many people worldwide will have access to flu shots if H5N1 avian flu triggers a pandemic. The data could illuminate a way to stretch the globe's meagre flu vaccine output, in Biblical loaves-fishes style, in response to a possible H5N1 crisis. The trials are expected to provide the first real evidence of whether adding an inexpensive and readily available chemical called alum to an H5N1 vaccine will substantially lower the dosage required to protect people against the worrisome strain. Currently, the world's flu vaccine plants can produce enough antigen to vaccinate about 450 million people a year, or just over seven per cent of the world's population. And that's only if two standard doses - of 15 micrograms each - are sufficient to achieve protection. Conversely, they could dash hopes that such a solution is at hand, leaving the hard realization that until additional vaccine capacity has been built and licensed some years down the road, vaccine will remain an option for a privileged few should a pandemic strike. But the first and to-date only publicized results from an H5N1 vaccine trial showed it took 12 times that much vaccine to protect each person. That dosing regime would mean only 75 million people or 1.2 per cent of the globe's population could be vaccinated in the first year of a pandemic.

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