A Long, Slow Journey
	Searching for A Vaccine
	By Bryan Walsh Hong Kong

Posted Monday, February 2, 2004; 21:00 HKT
You might think this would be an opportune moment to throw every available resource into developing a human vaccine capable of stopping avian flu. After all, it's spreading like the plague, and health officials openly worry that the world is only a roll of the genetic dice away from a human pandemic that could rival the 1918 Spanish flu, which claimed up to 40 million lives. But the slow-motion reality is less reassuring. Even though there is no available human vaccine for avian flu[EM]meaning the world's population has little defense, physiological or medical, against a possible pandemic[EM]production of a new vaccine won't begin until the disease shows "significant human-to-human transmission," says Dr. Klaus Stohr, head of the influenza team at the World Health Organization (WHO).

Under the WHO's aegis, laboratories in the U.S. and in Britain have begun preparing a vaccine seed from viral specimens taken from the current outbreak, but development and testing of the new vaccine could take up to half a year. Even then, says Stohr, "we will not have vaccine available for the whole globe." It would be "unrealistic" to expect more, says Stohr, because starting up a global vaccine-production program on short notice is like trying to turn an aircraft carrier on a dime. Nine pharmaceutical companies make more than 90% of the world's influenza vaccine, and they are already tied up producing human-flu vaccine. Diverting those resources to stockpile an avian-flu vaccine that might not be necessary will take up time and would disrupt the supply of human-flu vaccine. "To develop a vaccine up to the point where it can be used for human beings takes a lot of resources," says Professor Paul K.S. Chan, a virologist at the Chinese University of Hong Kong. "We really need to assess that need."

The deadly nature of the bird-flu virus presents another obstacle. Flu vaccines are traditionally made from viruses cultured in fertilized hen eggs, but H5N1 is as lethal to the embryo inside an egg as it is to adult birds. Instead, vaccine developers will have to use a new process called reverse genetics, in which scientists genetically engineer a weakened version of the virus so that it can grow in eggs and won't pose a threat to the researchers. But given that no vaccine derived from reverse genetics has ever been through full clinical trials, the process might be slower than normal procedures.

If H5N1 causes a pandemic in humans before a vaccine is ready, doctors will have to fall back on available drugs for standard flu. Unfortunately, the current strain of H5N1 is already showing resistance to amantadine, a cheap and widely available antiflu drug. Doctors are confident that a more expensive drug, Tamiflu, will remain effective against H5N1, but supplies are limited, and the impoverished Asian nations on the front line of any future pandemic will be hard-pressed to pay for treatments.

The good news is that making a vaccine for flu, even a new strain of avian flu, is easier than creating one for an entirely novel disease, as was required for AIDS and SARS. Although H5N1 has proved mutable, the WHO is confident that a new vaccine will remain effective even if the virus undergoes a genetic shift that enables it to pass easily between humans. Still, our best bet is to stop the virus in animals before a human vaccine ever becomes necessary. Says Dr. Yi Guan, a SARS and avian-flu expert at the University of Hong Kong: "Once this virus can spread from human to human, region to region, it's too late."

	Playing Chicken [January 26, 2004] Thaksin Shinawatra's government comes clean on the extent of avian flu in Thailand On High Alert [January 19, 2004] From Japan to Vietnam, Asian countries are culling millions of chickens infected with a strain of bird flu that can also prove deadly to humans. Can they prevent a pandemic? The Cycle of Death [April 7, 2003] SARS is only the latest in a string of epidemics to emerge from southern China Hong Kong's Fowl Problem [February 15, 2002] Hong Kong's latest bird flu scare points to a lack of Chinese cooperation More Related Items | Search all issues of TIME Magazine