BANGKOK, Thailand (AP) _ A new human bird flu vaccine being tested in the United States is a good step toward preventing a potential pandemic, but it shouldn't be mistaken for a ``silver bullet,'' the World Health Organization said Monday.
The promising results were based on a study involving healthy adults and did not include testing on children, the elderly and people with chronic illnesses _ the most vulnerable groups to flu _ raising questions about the vaccine's overall effectiveness, said Dick Thompson, a WHO spokesman in Geneva.
``This is a good beginning,'' Thompson said of the results. ``Is it perfect to produce? Is it the silver bullet? No, it's not, but it's a good start.''
Dr. Anthony S. Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases, who oversaw the study, announced over the weekend that preliminary data showed the vaccine produced an immune response in the first 115 people tested. Similar results are expected for the 185 others involved in the trial, he said.
But he also said the vaccine is difficult to produce and is only effective if given in large doses.
Other scientists say the development of any bird flu vaccine must be accompanied by international programs to distribute it in countries where a pandemic is likely to originate _ most likely in Asia where many poor countries will not be able to afford it.
Governments and international health officials are rushing to make preparations for the next flu pandemic, which experts say could kill millions of people and may emerge from a mutated strain of the avian flu virus that has swept Asia.
Some wealthy countries are stockpiling millions of doses of antiviral drugs like oseltamivir, known commercially as Tamiflu, while scientists are working on a vaccine.
Fauci said the U.S. government is ready to order significantly more than the 2 million doses it has already acquired from a French vaccine maker, and he predicted the U.S. Food and Drug Administration could approve the vaccine soon.
Thompson warned that if a flu pandemic ignited, the availability of any vaccine and antiviral drugs would be ``extremely limited'' and ``the reality is that ... we need to make decisions now about how we deal with a pandemic with those restrictions.''
Dr. Yuen Kwok-yung, a microbiologist at the University of Hong Kong, also welcomed the American development as an ``important step'' that showed vaccines could be developed quickly to battle possible mutations of the virus.
But the problem, in the event of a pandemic, of getting enough vaccine to people in poorer countries such as Vietnam, Thailand and Indonesia, where most of the 60 bird flu deaths have occurred remains unsolved.
``When the pandemic comes, it is difficult to have enough vaccines for those in the poorer area of the world because those who can produce it may hold it up for their own citizens,'' Yuen said.
He said the WHO should coordinate the stockpiling of drugs to combat the pandemic in places where it is likely to break out.
Thompson, speaking by telephone from Geneva as scores of WHO and other officials met in Bangkok, Thailand to discuss promoting health issues, said: ``There are a lot of steps along the way before we get to a vaccine that we're going to feel confident about and that will be widely used. We're a ways from that.''