Northern hemisphere countries have so far ordered more than one
billion doses of swine flu vaccine, the World Health Organisation said.
This intense demand coupled with production delays could create
shortages, forcing governments that are preparing for a second,
possibly more deadly, wave of flu in the fall to make hard choices
about who to vaccinate first, experts said.
"Pandemic vaccine orders put in by northern hemisphere countries
stand at over one billion," WHO spokeswoman Melinda Henry said.
"In the early days, there will be a very limited supply of
vaccine. There won't be sufficient supply to vaccinate whole
populations, or even huge proportions of populations," Henry said.
Some countries -- notably Greece, The Netherlands, Canada and
Israel --have ordered enough double doses to inoculate their entire
Others, such as Germany, the United States, Britain and France,
have put in orders that would cover between 30 and 78%.
Clinical tests ‘not encouraging’
In July, the WHO said that the 25 drug companies which had
announced their intention to manufacture vaccines could crank out
up to 94 million doses per week starting in mid-October.
The global health body revised these numbers sharply downward
when the top half-dozen vaccine makers -- accounting for 85%
of global production -- reported that the swine flu strains with
which they were working did not reproduce as quickly as expected.
"The current vaccine strain would only yield 25 to 50%"
of the original estimate, as low as 23 million doses per week, said
Clinical tests have not yet confirmed whether new strains under
development will produce higher yields, and initial results for at
least one, reviewed by WHO, are not encouraging.
There remains a big question mark, Henry said, as to whether one
or two doses will be needed for effective vaccination.
Double does may be needed
A Chinese drug company, Sinovac Biotech, announced that
it had completed clinical trials showing that its new vaccine
"induces good immunogenicity after one dose".
But many experts have said that double doses will be needed
because most people have no immunity to the so-called "novel"
Even with these uncertainties, a rough calculation shows a
sizable gap between firm orders and potential supply in the coming
months, a shortfall that will oblige national health authorities to
essentially ration the vaccine.
"Policy makers are still coming to terms with who the target
groups should be," said Mark Miller, an epidemiologist at the
Fogarty International Centre of the US National Institutes of
Virtually all international and national health authorities say
health sector professionals should be vaccinated first, because
they are frequently exposed to the virus but above all to insure
that health facilities can operate at maximum efficiency during
peak periods of infection.
Beyond that, there are no universal guidelines.
Experts differ on priority vaccinations
"Individual countries have to look at their own conditions and
adapt. They have to decide whether they want to stop transmission,
protect essential infrastructure, or reduce illness and death,"
Each of these priorities imply different strategies, and entail
protecting different sectors of society.
Some experts recommend vaccinating all school-age children and
their parents to stop the flu from spreading, while other say
vulnerable populations must be first in line.
But even knowing who is vulnerable is a problem, experts say.
Historically, during seasonal flu epidemics, priority has gone
to the elderly and those with chronic diseases, such as asthma or
other lung conditions.
Not all pandemics the same
"But we know from our research that it is actually younger
populations which are more affected during pandemics -- it is one
of the signature features of pandemics," Miller said.
In a study published in 2008, Miller showed that each of the
20th century's major pandemics would have required a different
vaccination strategy in order to save the maximum number of "years
of life lost".
Had vaccines existed at the time, inoculated persons under 45
would have been best in 1918. For 1957, the ideal target would have
been adults over 45, and for 1968 adults between 45 and 64, the
study found. – (Sapa, August 2009)
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