In the intellectual race against a possible avian flu pandemic, scientists such as Dr. Robert Edelman are beginning to talk publicly about a new idea.
Why not, the University of Maryland vaccine expert suggested recently to a group of Israeli doctors at Ben Gurion University Hospital, combine the avian influenza vaccine with the one for the regular flu?
"I presented the idea, and everyone jumped on it," said Edelman, one of several scientists pondering the notion to help ward off the bird flu in people.
But would it be a perfect solution? Hardly, as even Edelman attests. Instead, the idea shows the complexity of the riddle confronting public health authorities and the physicians and scientists who advise them.
The challenges include whether to vaccinate against avian flu when it has yet to spread from person to person, given all vaccines' risk of side effects. And there are manufacturing and scientific challenges, including how to engineer the vaccine so it packs more punch.
As bird flu spreads sporadically from flocks to people in a growing number of countries -- most recently, Turkey -- scientists look for flu-fighting solutions in hopes of preventing a pandemic. The World Health Organization says the disease has killed 80 of the 149 people confirmed to have contracted it, mostly in Asia.
Scientists are working hard to stay ahead of it. They are sequencing the genomes of dozens of strains of influenza to deduce how to disable them. They are testing different ways to make bird flu vaccine, including using eggs, using animal cells in big, brewerylike vats, and using cells from insects.
They're also exploring various ways to administer it, including injecting it into muscle or in the skin and spraying it up the nose. Another option might be to use a skin patch similar to the one people wear to quit smoking.
At the University of Maryland School of Medicine in Baltimore, clinical trials in about 150 healthy adults found no serious side effects. Trials will test whether adding a chemical to one version of the vaccine -- which now requires at least two shots to produce effects -- will make a smaller dose work better.
A combined vaccine is yet another idea designed to help ward off the spread of a virus that -- while now passed only from birds to people -- might change into one that could spread swiftly from person to person.
Dr. Bruce Gellin called the idea of priming the human immune system to develop a memory for potential pandemic viruses "an attractive immunological theory." But the director of the National Vaccine Program Office, part of the Department of Health and Human Services, cautioned that "we need to develop a sound scientific database before it can be considered as a public health policy."
The combination might help people fight off avian flu, if it ever began spreading among humans, scientists speculate. And the prospect of added protection might encourage people to get the annual shot, boosting the limited demand and relatively puny profits that have driven many companies out of the vaccine business, the thinking goes.
"All these considerations being expressed are worthy of careful analysis and investigation," said Dr. Roland Levandowski, chief of a National Institutes of Health section that studies respiratory diseases, including flu. "I think we need to make all the preparations we can."
To understand the proposed solutions, it's helpful to understand what public health authorities see as the major challenges of fighting avian flu.
First, influenza generally spreads quickly, potentially thwarting the effectiveness of quarantines.
A second challenge is that there aren't many manufacturers who want to make vaccines, and the ones that do are busy. Companies can make far more money with heart disease or cancer drugs, which are given repeatedly and sell for more than a once-a-year flu shot.
The seasonal flu vaccine must also be made fresh yearly, because the strains of the flu circulating change from one year to the next. Demand for the shots also fluctuates, subject to a fickle public, and what flu vaccine isn't sold each year must be thrown out.
As a result, there are only four companies licensed to sell seasonal flu vaccine in the United States. Production takes months, and manufacturing plants are few, meaning companies wouldn't be able to react quickly once avian flu began spreading.
Third, the avian flu virus spread among birds may be changing, and the exact strain scientists must target to protect people is not yet known. The virus has passed from birds to people who directly handle them but not from one person to another. Other changes in the virus may cause that to happen.
Viral changes mean any stockpiled avian flu vaccine might not be exactly the right one. And besides, the frozen vaccine has a shelf life of only about 18 months, said Dr. Phillip Russell, former director of the Walter Reed Army Institute of Research.