The optimistic projection is based on information provided at a meeting
called by the World Health Organization and three other international agencies
to prepare for a possible influenza pandemic. The projection assumes that the
bird flu virus now circulating in Asia and Europe -- or some other exotic strain
-- will not be able to infect people easily for at least several years.
The virulent strain of the virus, known as H5N1, has infected 124 people and
killed 63, according to WHO statistics. But so far, almost all of the people who
have contracted the disease had close contact with infected birds. The virus
does not pass easily among humans, but specialists say it could gain that
capacity over time through mutation or recombination with other strains of flu,
eventually leading to a pandemic.
For a vaccine to reach a quarter to a half of the world's population -- 1.7
billion to 3.4 billion people -- current plans by manufacturers to expand
production would have to go forward uninterrupted. In order to immunize the
maximum number of people, doses would also have to be used with
immunity-boosting substances that would make the vaccine more effective. The
projections assume there will be enough trained technicians and needles on hand
to administer the vaccines.
The projection of reaching up to 3.4 billion people also assumes the use of a
technique that would double the vaccine's potency, based on research being
Few specialists think that everything will go so smoothly. WHO, which has
analyzed global vaccine production, is unwilling to certify the projection of
3.4 billion vaccinations. Nevertheless, even the projection of 1.7 billion
represents a major expansion over the current annual production of 300 million
seasonal flu shots.