Researchers Race to Boost Supply of Bird Flu Vaccine
Sunday, February 12, 2006
Medical researchers bracing for a global influenza epidemic are in frantic search of a way to perform a loaves-and-fishes miracle with the world's skimpy annual production of flu vaccine.
That production -- about 300 million flu shots a year -- cannot be increased quickly or easily, no matter how dire the circumstances. If the supply is going to protect more than a tiny fraction of the world's 6.5 billion people, some way has to be found to stretch it.
Nearly all the experts believe that a vaccine is the only tool capable of stopping a flu pandemic. They also agree the world is closer today to that potentially calamitous event than it has been in decades.
In the last six months, the H5N1 strain of "bird flu" that first caused human deaths in Hong Kong in 1997 has moved across Central Asia into Eastern Europe and Africa. Just in the last month, it has appeared in three new places: Iraq, Cyprus and Nigeria. Of the 150 confirmed human victims worldwide, 85 have died. All the virus needs to trigger a pandemic is the capacity to spread easily among humans.
To prepare for that -- to try to work the miracle -- biologists have turned to "adjuvants," substances added to conventional vaccines to increase their potency.
Adjuvants make small doses of vaccine act big. They focus the immune system's attention on the "antigen" -- the substance that stimulates the protective effect. Some adjuvants even broaden immunity and make it longer-lasting. Scientists do not know exactly how adjuvants do all this. But they do know they make it possible to dilute a vaccine with no loss of effect.
"The global demand for pandemic vaccines will be immense," said David S. Fedson, a physician, epidemiologist and former consultant to the World Health Organization. The only way to meet the demand, he believes, "is to use an adjuvant."
To pharmaceutical companies, these peculiar substances are hot properties.
"We are in possession of one of the key ingredients of a potential solution to the pandemic threat," said Howard Pien, president of Chiron Corp. The California biotech firm has an adjuvant, an emulsion called MF59 whose main constituent is shark-liver oil. It is already in use in a flu vaccine in Europe.
"We believe that the adjuvant may become the holy grail of vaccines," Chrystyna Bedrij, an analyst with Griffin Securities, wrote in November in a review of avian flu-related business.
Since their discovery in 1925, adjuvants have been mostly curiosities -- occasionally useful, occasionally dangerous. It now appears they will make or break a pandemic flu vaccine. Nineteen clinical trials of pandemic flu shots -- against H5N1 and three other types of avian influenza -- are scheduled to be run this year. Seventeen of the vaccines will contain an adjuvant.
But it probably will be an uphill battle. The only study completed of an H5N1 vaccine made in the manner of a traditional flu shot found that adding an adjuvant did not help much. The reason might lie as much with the virus as with the adjuvant. There is growing evidence that H5N1 is inherently less stimulating to the immune system than other influenza strains -- yet another dangerous trait it possesses.