HEALTH:
Pre-Pandemic Vaccine at the Forefront in Bird Flu Fight
Stephen Leahy*
TORONTO,
Jul 1 (Tierramérica) - Some 17 countries are hard at developing
experiments ultimately aimed at preventing the spread of bird flu
amongst humans. So far, avian influenza has killed 120 people. The
rapid production of effective, low-cost vaccines will not prevent a
pandemic from happening, but could sharply reduce its impact, say
experts.
In 28 clinical trials, scientists are testing
different forms of H5N1, the bird flu virus, to create pre-pandemic
vaccines, which could be a boon at a time when the much-feared mutation
that would facilitate human-to-human transmission has yet to occur.
"An unknown (mutated) virus could show up at any time, and
some of these (bird flu) efforts will help," John Treanor, a virus
expert at the University of Rochester School of Medicine, in New York
state, told Tierramérica.
Over the past year, newer strains of H5N1 have become highly
infectious amongst domestic and wild birds, but not in humans. However,
about 120 humans deaths have been linked to H5N1 since 2003 -- all the
result of close contact with infected birds.
The bird flu virus is evolving rapidly, making it very
difficult to predict whether there will be a pandemic or not, says
Treanor
Computer models have suggested that within three months a
pandemic virus could reach every continent. Within six to nine months,
it could reach every country. The bird flu could kill as many people as
the "Spanish flu" pandemic of 1918-1919, in which more than 50 million
people died, he said.
Once the mutated virus is identified, developing an effective
vaccine against a specific flu strain can take about six months.
Immunisation requires that some of the actual virus strain be injected
into our bodies to allow our immune system to build a defence against
the fully-functioning virus.
"Production cannot start before a pandemic strain of flu
emerges," said Klaus Stohr, head of the World Health Organisation's
(WHO) global influenza programme.
But efforts to come up with pre-pandemic vaccines are vital.
New reason for hope emerged two weeks ago with evidence that ferrets
immunised with a vaccine based on an H5N1 strain isolated in Hong Kong
in 2003 protected them against a newer variant of the virus.
Pre-pandemic H5N1 vaccines may stimulate a better immune response than
previously believed and merit being stockpiled as initial pandemic
vaccines, according to researchers at St. Jude Children's Research
Hospital in Memphis and the University of Tennessee, located in the
southeastern United States.
Human trials of other H5N1 vaccines are under way elsewhere, including
final phase-three trials by pharmaceutical giant GlaxoSmithKline,
involving 5,000 people from France, Germany, Netherlands, Russian
Federation, Spain and Sweden.
CSL Limited, an Australian pharmaceutical company, is also
studying the safety and effectiveness of its new vaccine in humans this
year.
The French laboratory Sanofi Pasteur has reported that its vaccine
produced a good immune response in two-thirds of the volunteers tested,
but more research is needed. Among the challenges is reducing the
amount of vaccine needed to confer immunity so that the drug will be
available to more people.
Worldwide, vaccine manufacturing has been on the decline for several
years, mainly because there was little profit in providing vaccines for
common childhood illnesses.
Instead, drug companies focus on medications for the ageing populations
of industrialised countries. Even seasonal flu vaccines were in short
supply in the United States because low manufacturing capacity.
Currently, the combined output of the world's flu vaccine manufacturers is about 900 million 15-milligram doses of antigen.
The Sanofi Pasteur H5N1 vaccine requires two 30-mg doses of antigen,
and even if it were fully effective only 225 million could
theoretically be protected.
To counter this shortage, a number of countries and companies are
making new investments. In May, the U.S. government awarded five
contracts totalling more than one billion dollars to develop cell-based
technologies for making flu vaccines.
Traditionally, vaccines are made by injecting the virus into chicken
eggs, where it replicates within the embryo. The method is slow,
requires a lot of space and one or two eggs per dose of vaccine --
obviously a problem if bird flu decimates chicken populations.
Producing flu vaccines in cell cultures, as is done with polio,
hepatitis A, and chickenpox vaccines, would be faster and a more
flexible approach. And the large pharmaceutical giants are seizing on
this new opportunity, buying and building vaccine manufacturing
facilities.
But few of these facilities are outside of the developed world.
Brazil announced last month that it will invest 13.6 million dollars to
build a new manufacturing plant for seasonal flu vaccine, scheduled to
open in 2007. It will be "a world-class plant, the first in a
developing country," says Jarbas Barbosa da Silva, Jr., undersecretary
of health surveillance for Brazil's Ministry of Health.
In addition, a "pilot unit" will begin production of a
pandemic influenza vaccine based on H5N1 this month, Da Silva said in a
statement.
Even if the dreaded bird flu pandemic fails to materialise, the
billions of dollars invested in research and manufacturing will not be
wasted, said virus expert Treanor. The results will help when some new,
unknown virus appears.
(*Stephen Leahy is a Tierramérica contributor. Originally published
June 24 by Latin American newspapers that are part of the Tierramérica
network. Tierramérica is a specialised news service produced by IPS
with the backing of the United Nations Development Programme and the
United Nations Environment Programme.)
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