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HEALTH: Pre-Pandemic Vaccine at the Forefront in Bird Flu Fight

Stephen Leahy* - Tierramérica

TORONTO, Jul 3 2006 (IPS) - 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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